Cu(In,Ga)Se₂ (CIGS) thin films were prepared by selenization of metal precursors using van Doorn apparatus. The apparatus provides advantages such as superior Se pressure controllability and simplicity. XRD measurements revealed that the selenized films had a chalcopyrite structure. EDX measurements revealed that the Ga ratios decreased with increasing selenization temperature, while Se ratio increased. SEM measurements revealed that the films had relatively large grains and roughness. V_oc= 495 V, I_sc= 2.9 mA/cm² and F.F.=0.24 were obtained. EQE spectrum indicated a small diffusion length of minority carriers for longer wavelength region. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Mg₂Si is expected as a candidate for environmental-friendly material of a thermoelectric device. Nano-crystallization is considered to be one of the most effective approaches to improve thermoelectric property. If grain grows up during sintering, we are afraid not to obtain nano-effect. We have, therefore, investigated grain growth during sintering. We have found that grain growth is not observed if particle size distribution of starting powder is relatively uniform. On the contrary, grain growth is observed if it is relatively not uniform. We have concluded this may be due to un-uniformly distributed current during sintering. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Transparent conductive oxide Zn(O,S):Al (AZOS) films with S/(S+O) 0.00 to 0.25 were fabricated by co-sputtering of ZnO:Al and ZnS targets. All films showed high transparency of over 80% with edge shift at short wavelength which showed band gap changed as S/(S+O) increased. However, sheet resistance increased with increased S/(S+O), with over 10⁴ Ω/sq at S/(S+O) of 0.25. These films were used in the fabrication of buffer-less Cu(In,Ga)Se₂ solar cells with cell structure of Al/NiCr/AZOS/CIGS/Mo/SLG. The cell performance increased with S/(S+O), with highest efficiency of 9.05% at S/(S+O) 0.09. However, at higher S/(S+O) cell performance dropped and at 0.25 no cell performance was recorded which was due to the high sheet resistance. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper, we report a new type Auger-free luminescence (AFL) of Rb₂ZnCl₄ crystals. Until now AFL has been reported in alkali and alkali-earth halides. This luminescence originates from electon transitions from the valence band of halogen p orbitals to the top of outermost core levels of alkali or alkali-earth p orbitals (p-p transitions). On the other hand, the AFL of Rb₂ZnCl₄ is expected to be of p-d type, in which the electronic transitions from Cl 3p orbitals are terminated by outermost Zn 3d core levels. The electronic states concerning are apparently different from those of alkali and alkali-earth halides. The finding of such a peculiar AFL is achieved by comparison between results of spectroscopy experiment and cluster calculation. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Parasitic thermal effects (thermal depolarization and thermal lens) of three Konoshima Chemical Co. laser-ceramics samples Yb³⁺:Lu₂O₃(C_Yb≈1.8%), Yb³⁺:Y₂O₃(C_Yb≈1.8%), and Yb³⁺:Sc₂O₃(C_Yb≈2.5%) were measured in experiment at different pump power. The obtained results were used to calculate a number of thermo-optical constants, which showed that sesquioxide ceramics are significantly superior to the widely used yttrium aluminum garnet Yb³⁺: Y₃Al₅O₁₂(C_Yb≈10%). (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu₂ZnSnS₄ (CZTS) thin film solar cells have been fabricated using sol-gel sulfurizing method under non-vacuum processing. The solar cells structure is Al/ZnO:Al/CdS/ CZTS/Mo/Soda Lime Glass(SLG) substrate. In our previous reports, the surface of CZTS got rougher as the particle diameter increased. In addition, there were many spots where CZTS layer was not coated enough by ZnO:Al window layer. In this report, in order to improve conversion efficiency of the CZTS solar cells, we focus on the ZnO:Al layer and the effect of an increase in the number of ZnO:Al coating repetition and the dependence on drying time and temperature for ZnO:Al were investigated. Optimized conversion efficiency of 3.61% was achieved with 15 coating repetition of ZnO:Al layer coated at 350 °C and dried for 3 min. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Micro-structure of AgInS₂ grown by the hot-press method has been examined by the properties of free-exciton emission using a scanning confocal-microscopy system. The crystal structures are distinguished by a two-dimensional image of free-exciton emission at RT. The excitonic emissions with the orthorhombic structure were also analyzed and a bound exciton emission was observed in addition to a free exciton emission. Furthermore, it is indicated that the two-dimensional image of decay-time constant is more insusceptible to resolve the structures than that of emission intensity. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic structures of the ternary-layered semiconductor TlGaSe₂ have been investigated by hard and soft X-ray photoemission spectroscopies (HAXPES and SXPES). The spectral shape of all core levels obtained from HAXPES and SXPES can be represented by a symmetric Lorentzian, reflecting the semiconducting nature of TlGaSe₂. Peak positions of the same bulk components, obtained from HAXPES and SXPES, are almost the same. This suggests that the recoil effect is ignorable for TlGaSe₂ and that the HAXPES spectra of this material provide us the information on the intrinsic bulk electronic structures. The valence-band HAXPES spectrum is composed of two main features and is well reproduced by the theoretical calculation. The estimated value of 2.0 eV for the energy gap is consistent with the results from the optical measurements. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The ternary compound semiconductor Cu₂SnS₃ (CTS) is formed from non-toxic materials that are abundant in Earth's crust and other low-cost elements. CTS has also been reported to a band gap energy range of 0.93–1.77 eV and an absorption coefficient of 1.0×10⁴ cm^–1. Consequently, CTS is a potential material for the p-type absorber layer of thin film solar cells. In this study, we examined the dependence of the optical, electrical and photovoltaic properties of CTS thin films on the Cu/Sn composition ratio. CTS thin films were fabricated by sulfurizing evaporated Cu-Sn precursors with different Cu/Sn composition ratios at 560 °C for 2 h in a N² atmosphere and sulfur vapor. The Cu/Sn composition ratios of the sulfurized films were determined to be 1.6–2.5 by X-ray fluorescence. The solar cell comprising a CTS thin film with a Cu/Sn composition ratio of 1.77 exhibited the best performance among the cells examined, an open-circuit voltage of 242 mV, a short-circuit current density of 28.9 mA/cm², a fill factor of 41.7% and a conversion efficiency of 2.92% were obtained. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu₂Sn(S_1–xSe_x)₃ (CTSSe) solid solutions with 0 ≤ x ≤ 1.0 were synthesized by mixing the elemental powders and post-annealing at 600 °C. The crystal structure of Cu₂SnS₃ (CTS), Cu₂SnSe₃ (CTSe), and their solid solution were determined by Rietveld refinement of the powder X-ray diffraction data. CTSSe solid solution had a monoclinic crystal system [space group: Cc (No. 9)]. The refined lattice parameters of CTS were a =6.654(8) Å, b =11.534(2) Å, c =6.659(4) Å, and β =109.40(5)° and those of CTSe were a =6.964(6) Å, b =12.056(6) Å, c =6.972(4) Å, and β =109.49(1)°. The lattice parameters, a, b, and c of CTSSe solid solution monotonically increased with increasing Se content. The band gap of the CTSSe solid solution linearly decreased from 0.87 eV (x=0.0) to 0.67 eV (x=0.60) with increasing Se content. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Raman spectra of layered ternary thallium chalcogenide TlInS₂were studied with the aid of 3D confocal Raman system over the temperature range 77–300K in the frequency region of 120–400 cm^–1. The observed lines in the obtained Raman spectra were denconvoluted into Lorentzian peaks and temperature dependence of each peak's parameters (peak position and half width at half maximum) were obtained. An irregular behaviour of the temperature dependence of Loretzian parameters is reported. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical second harmonic generation (SHG) has been studied in TlMeX₂ (Me=In,Ga, X=S,Se,Te) compounds with layered and chain crystalline structures. For layered TlInS₂ and TlGaSe₂, SHG signal has been observed in a range of temperatures below the point of phase transition into ferroelectric phase for which asymmetry is prominent. On the other hand, the chain TlInSe₂ and TlGaTe₂ have shown SHG signal at a temperature above 270 and 293K, respectively. Both the TlInSe₂ and TlGaTe₂ have symmetry centre at room temperature and second order optical non-linearity is an artefact incompatible with their bulk structure. Surface structure is speculated to be responsible for SHG signal observed in these materials for the first time to our knowledge. The details of temperature behaviour of SHG in TlInSe₂ and TlGaTe₂lead to a phase-transition based model for explanation of the observed phenomenon. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical second harmonic generation (SHG) has been studied in TlMeX₂ (Me=In,Ga, X=S,Se,Te) compounds with layered and chain crystalline structures. For layered TlInS₂ and TlGaSe₂, SHG signal has been observed in a range of temperatures below the point of phase transition into ferroelectric phase for which asymmetry is prominent. On the other hand, the chain TlInSe₂ and TlGaTe₂ have shown SHG signal at a temperature above 270 and 293K, respectively. Both the TlInSe₂ and TlGaTe₂ have symmetry centre at room temperature and second order optical non-linearity is an artefact incompatible with their bulk structure. Surface structure is speculated to be responsible for SHG signal observed in these materials for the first time to our knowledge. The details of temperature behaviour of SHG in TlInSe₂ and TlGaTe₂ lead to a phase-transition based model for explanation of the observed phenomenon. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In Situ ellipsometric study has been carried out during the deposition of the CuInSe₂ thin film by means of the three-stage process. A rotator analyzing ellipsomerter using a 632.8 nm He-Ne laser was used. Ellipsometric parameters (Ψ and Δ) and reflectivity R was obtained during the entire deposition stages, in which a complex reflection coefficient is ρ=tanΨ exp(iΔ). Cu, In and Se were deposited on the Mo-coated SLG substrate. At the first-stage (In-Se deposition), the In-Se film deposition rate and its reflactive index has been obtained on the basis of the light interference. At the second-stage, changes in both Ψ and Δ are observed. Based on the X-ray diffraction measurement, these changes are related to the stoichiometric composition of the film from In-rich to Cu-rich. This signal was utilized as a process switch from the second-stage to the third-stage. At the third stage, the weak change in Ψ has been observed showing the change of the stoichiometric composition from the Cu- rich to the In-rich. By means of the in situ ellipsometry-controlled three-stage process, the CuInSe₂ layer with single phase chalcopyrite structure has successfully been prepared, which exhibits an intense near-band-edge photoluminescence at 0.998 eV at room temperature. The preliminary fabricated ZnO/CdS/CuInSe₂ solar cell exhibited a conversion efficiency of 5.6%. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Long afterglows are observed in the case of co-doping CaGa₂S₄ with Eu and one of the other rare earth elements (REEs). Thermoluminescence spectra of these compounds have been measured in order to determine their trap depths. Photoluminescence spectra and decay curves have been also observed. The emission intensities, decay times and trap depths are shown as a function of the f-electron number of REEs, and the correlation between these properties and the 4f and 5d levels of divalent and trivalent REEs in the band structure of CaGa₂S₄ is discussed. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The original design of the infrared detector providing ultrahigh parameters of responsivity is proposed. The idea lies in separation of the areas between charge carrier optical generation and formation of electrical signal. The calculations performed for Cd_xHg_1–xTe photodetectors with x ∼ 0.21 and x ∼ 0.28 at electric bias 200 mV yield values such as S_u = 10⁸–10¹⁰ V/W for voltage response. That is several orders of magnitude more than experimentally reached values for Cd_xHg_1–xTe-based IR-detectors (S_u =10⁶V/W for _λc = 11 µm, T = 77 K [Singh and Mittal, Def. Sci. J. 53(31), 281 (2003)]). Offered detector is different with very large resistance and small power consumption and dimensions of active area. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical constants of CdS:O window layers for solar cells were studied as a function of the oxygen content. The CdS:O thin films were deposited on glass substrates in the presence of oxygen at 0, 2, 3 and 5% values of O/Ar ratio by rf magnetron sputtering. Ellipsometric measurements on CdS:O thin films were carried out over 0.75–6.0 eV photon energies at room temperature. Optical constants were determined by using a the best-fit dispersion model. Broadening of spectral features of the obtained optical constants is found to increase with increasing O/Ar ratio. Besides, the CdS:O films grown at 100 °C as compared to those grown at 200 °C exhibit increased spectral broadening. In fact, almost complete smearing of band gap spectral feature is observed for CdS:O films deposited at 5% value of O/Ar ratio, resulting in appreciable transparency of the films in a spectral range above the energy gap of CdS. This, in turn, leads to an increased carrier collection in the UV spectral range and allows to considering CdS:O film as a candidate for improved window-layer material for solar cell application. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu(In,Ga)Se₂ (CIGS) thin films were deposited on the Mo/heat-resistant glasses (SS-8, Nippon Electric Glass) by the three-stage evaporation process. The coefficient of thermal expansion (CTE) of SS-8 is 8.4×10^–6/K, strain point of SS-8 is 582 °C. SS-8 has the CTE similar to that of SLG but higher thermal tolerance. Substrate temperature (T_sub) during deposition and Ga/(In+Ga) atomic ratio of CIGS thin films were controlled to 550∼600 °C and 0∼0.7, respectively. The effect of T_sub and Ga/(In+Ga) atomic ratios of CIGS films have been characterized by electron backscatter diffraction (EBSD) measurements. Grain size and ∑3 grain boundary ratio increased at higher T_sub. ∑3 grain boundary ratio was calculated from the fraction of the length of ∑3 grain boundary by the length of the total grain boundaries on EBSD image. There was the correlation among Ga contents, T_sub, grain size and efficiency. It is difficult to distinguish between effect of grain size and effect of grain boundary to efficiency. However, it is found that high Ga content up to 0.7 results in both high efficiency and ∑3 grain boundary ratio. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Four-quantum-well structure consisting of a ZnCdMnSe diluted magnetic semiconductor (DMS) well and three ZnCdSe non-magnetic semiconductor (NMS) wells separated by 15 nm-thick ZnSe barrier layers were prepared by using ALE and MBE technique. The sample was excited by CW and pulse lasers with photon energy larger than the barrier layer band gap, and circularly polarized PL spectra due to recombination of excitons localized in each well were measured as a function of external magnetic field in the Faraday geometry up to 8 T at 4 K. The PL from the NMS well next to the DMS well and from the NMS well next-but-one to the DMS well showed positive circular polarization due to LO phonon assisted transfer of positively spin polarized excitons from the DMS well to the NMS wells. The two NMS wells showed different magnetic field dependence of the degree of circular polarization of PL, which suggested that the exciton transfer from the DMS well to the NMS well next-but-one was governed by direct interaction between the two wells, not by cascade transfer process. The degree of circular polarization of PL from the NMS wells increased from zero to 20∼30% after pulse excitation. Raise time of the polarization degree was discussed on the basis of the difference of distance between the NMS well and the DMS well. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Wurtzstannite-type Cu₂ZnGeS₄, Cu₂ZnSiSe₄ and Cu₂ZnSiS₄ single crystals were grown by chemical vapor transport method using iodine as transport agent. Raman spectra of obtained crystals were investigated and 17, 11 and 18 peaks were observed for Cu₂ZnGeS₄, Cu₂ZnSiSe₄ and Cu₂ZnSiS₄, respectively. In all cases, the spectra from these compounds are characterized by three dominant peaks. In case of Cu₂ZnSiSe₄ the dominant peaks appear at 222 cm^–1, 179 cm^–1 and 170 cm^–1. For Cu₂ZnGeS₄ and Cu₂ZnSiS₄ the most intense peak shifts from 360 cm^–1 to 393 cm^–1 with replacement of Ge by Si, while the other main peaks have almost the same position for both compounds (272–278 cm^–1 and 291 cm^–1). Identification of these dominant peaks provides with a characteristic spectral fingerprint for detection of these crystalline phases. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

ESR measurements have been carried out to determine the local environment and the ground state of Ce³⁺ ions in the orthorhombic CaGa₂S₄ at 4.2 K. More than 30 ESR lines are observed with almost the same angular dependence. The local symmetry and the anisotropic g-tensor for the four strongest ESR signals indicate that Ce³⁺ ions substitute the three independent Ca sites. A part of Ce³⁺ ions at the Ca²⁺ sites and a neighbouring sulphur vacancy are expected to form complex centers in view of the other weak ESR lines observed. The ground state of Ce³⁺ in the host lattice is shown to consist of mostly ϕ_±1/2 by fitting the ESR spectra using the spin Hamiltonian. The upper ²F_7/2 state is thought to be slightly mixed into the ground state ²F_5/2 judging from a small difference in the fitting. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

ZnS films are formed by spray method using various zinc sources such as zinc acetate (Zn(CH₃COO)₂), zinc sulfate (ZnSO₄), zinc nitrate (Zn(NO₃)₂), zinc iodide (ZnI₂), zinc chloride (ZnCl₂), zinc acetyl (Zn(acac)₂). ZnS film using zinc iodide is sharp spectrum and zinc sulfate is broad spectrum by X-ray diffraction (XRD). The XRD spectra indicates that ZnS using zinc chloride and zinc iodide at 100 °C the source of zinc to zinc acetate and zinc nitrate at 200 °C, zinc acetyl at 300 °C, zinc sulfate at 400 °C can be confirmed. These results are consistent with the difference in the instability constants of each zinc source. The ionization of Zn becomes difficult with increasing the instability constant of zinc sources. Reaction is slow due to low ionized zinc in solution. Therefore, it is considered that ZnS films are hard to crystallize at low substrate temperature. The grain size becomes large with decreasing the instability constant. It is considered that this is proportional to the amount of zinc ions in solution. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We tried to recycle CIGS thin film solar cell absorber layer as a deposition source. The deposition source is peeled off from Mo/SLG substrate. The recycled-CIGS films were evaluated by XRD, Raman scattering spectroscopy, and SEM. As compared with high-efficiency CIGS films, the XRD patterns and Raman spectra show that the crystallinity of deposited CIGS film using peeling-off powders was similar. A secondary phase is not generated on the surface of the deposited CIGS film by SEM observation. From these results, we thought that the CIGS materials from solar cell structures were able to be recycled for new solar cell absorber layer. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The 2-MeV electron radiation damage of Si_1-xGe_x source/drain (S/D) p-type metal oxide semiconductor field effect transistors (p-MOSFETs) with different Ge contents is studied. Before electron irradiation, an enhancement of the hole mobility with Ge content of the S/D stressors is clearly observed. On the other hand, after electron irradiation, the drain current and the maximum hole mobility decreases with increasing electron fluence for all Ge contents, because of lattice defects are introduced by the electron irradiation in the Si channel. The threshold voltage shifts and the maximum hole mobility degradation is independent on the Ge content for all electron fluences. These results indicate that the strain-induced hole mobility enhancement due to Ge doping is retained after electron irradiation in the studied device structure. This indicates that the compressive strain is maintained in the channel. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Porous CuInS₂ crystals were grown from starting materials CuCl₂·2H₂O, InCl₃·4H₂O and thiorea with ethylene glycol solution, that were placed into a flask, heated, and refluxed for 1 hour. The diffraction peaks only from CuInS₂ phase appear for all the samples. The morphology of CuInS₂ crystal was porous, and the porous crystals exist in two kinds. One kind was flower-like crystals which complexly lack the flakes, another one was sphere-like crystals existed with a number of the poles. The specific surface area of the samples grown by stirring starting materials with In to Cu ratio of 4.3 for 30 minutes was found approximately to be 55 m²/g. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu₂ZnSn(S_1−x,Se_x)₄ (CZTSSe) solid solution films were prepared on Ti foils by means of non-vacuum, instantaneous, direct synthesis from elemental Cu, Zn, Sn, S, and Se precursor films using microwave irradiation. XRD patterns and Raman scattering spectra show that the resulting films consist of CZTSe crystals. The lattice constants of CZTSSe decreased in direct proportion to the S/(S+Se) ratio almost satisfying Vegard's law. Resulting films were relatively compact and continuous in the inner part. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical properties of the Cu₂ZnGeS₄ bulk single crystals were characterized by using Raman spectroscopy and photoluminescence spectroscopy technique. The strongest lattice vibration mode of this compound observed at 359 cm^–1 and less intensive modes at 273, 291, 332, 370, 383, 405 and 414 cm^–1. PL spectra of the Cu₂ZnGeS₄ consist of dominant broad emission band located at about 1.40 eV and a less intensive near 2.00 eV at 4.5 K. The observed PL bands were attributed to the donor acceptor pair transitions, with activation energy of 37 (140) meV for dominant and less intensive band, respectively. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A new mechanism of nucleation during mechanosynthesis of complex oxides, based on the mass transfer due to plastic deformation is reported. Preparation of optical ceramics shows the role of the twinning process in the nucleation of yttrium aluminum garnet (Y₃Al₅O₁₂) and spinel (MgAl₂O₄) by grinding powders of Al₂O₃ + Y₂O₃ and MgO + Al₂O₃, respectively. A new look at the role of twinning in the plastic deformation suggested that mechanical twinning is the main mechanism of mechanochemical solid-state reactions. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photoluminescence (PL) spectra in the band-edge region on bulk single-crystals of CuInS₂ grown by the traveling heater method have been investigated using a confocal microscopy system. The observed PL spectra are separated into two Lorentzian peaks which are assigned to be A and B free excitons, by the analysis of the excitation intensity dependence of the emissions. Consequently, we present the behaviour of B free exciton within a wide range of temperatures. The time-resolved emissions of A free exciton have also been examined. The decay of the emissions is analyzed using a double exponential curve. Fast and slow components are attributed to nonradiative relaxation and radiative recombination, respectively. The decay-time constant of the slow component corresponds to the radiative lifetime of A free exciton and is obtained over the wide temperature region until 300 K. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu₂ZnSnS₄ (CZTS) thin films were deposited on glass substrates by spray pyrolysis a fast, cost effective and vacuum-free method. X-ray fluorescence, Raman spectroscopy and grazing incidence X-ray diffraction, were used to characterize the obtained thin films. The analysis of these data showed a close to stoichiometry composition of the films and CZTS adopts the kesterite type structure but with poor crystalline quality and possible existence of secondary phases, such as ZnS and Cu₂SnS₃. An annealing procedure in presence of elemental Sn and S was applied in order to improve the quality of the films. The annealing leads to an improvement of the crystalline quality of the thin films. The lattice parameters a and c of the annealed CZTS thin films were obtained as result of the Rietveld analysis of the gracing incidence X-ray diffraction data. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High-grade Bi₂(Te_0.9Se_0.1)₃ thin films have been obtained and studied by means of confocal Raman spectroscopy and electrical measurements. The annealed films demonstrate the Raman-active modes, (61 cm^–1) and (101 cm^–1), which were not observed on as-grown samples. At densities of incident laser irradiation above 50 W/mm², the infrared-active modes, (95 cm^–1) and (120 cm^–1), emerge in the Raman spectra. The last fact is ascribed to symmetry breaking that is resulting from the internal stress and structural deformations caused by local over-heating. The obtained Bi₂(Te_0.9Se_0.1)₃ films manifest dielectric rather than metallic conductivity that is usually observed for bulky crystals of this sort. The variable range hopping conduction has been found to be dominant at temperatures below 100 K. Localization radius and density of localized states at Fermi level have been estimated. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Non-doped and Ga-doped ZnO film on glass substrate were successfully grown at 150 °C by conventional atmospheric spray pyrolysis using diethylzinc-based solution. The samples had an average optical transmittance of more than 80% and were strongly a-axis orientated according to the results of optical transmittance and X-ray diffraction analysis, respectively. The n-type Ga-doped ZnO films had a low resistivity of 2.3 × 10^–3 Ωcm, a carrier concentration of 1.1 × 10²⁰ cm^–3 and a mobility of 10 cm² (Vs)^–1 at an optimal Ga content of 2 at% upon UV irradiation. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Polycrystalline thin films of Sn_1−xPb_xS (0 ≤ x ≤ 0.5) were grown by multi-beam hot-wall deposition using SnS and PbS as source materials. Employing evaporation temperatures of T_PbS ≈ 680 °C and T_SnS ≈ 600 °C dendritic thin film growth appears due to high supersaturation at the substrate surface (T_Substrate ≈ 240…375 °C). Therefore, both evaporation temperatures were lowered to T_PbS ≈ 600 °C and T_SnS ≈ 540 °C. Calculated and measured thin film compositions agree very well. The variation of the deposition time exhibits linear thin film growth. At the very beginning of film growth a well-distinct texture can be observed. If the growth proceeds (t > 5 min) this texture disappears. As determined by transmission UV-Vis spectroscopy all Sn_1−xPb_xS films show a direct allowed transition which bandgap energy increases with increasing x and an indirect allowed transition which bandgap energy decreases with increasing lead content. Decreasing film thickness leads to an increase of both bandgap energies. The obtained results were discussed with respect to a possible application as absorber material in solar cells. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have studied structure and optical properties of CdS:O thin films deposited on soda lime glass substrates by rf magnetron sputtering in the atmosphere of oxygen/argon gases. According to X-ray diffraction and confocal Raman scattering data, the films deposited under oxygen partial pressure below 3% show crystalline structure of CdS. On the other hand, X-ray diffraction, confocal Raman scattering, TEM (transmission electron microscopy) and XPS (X-ray photoelectron spectroscopy) data are indicative of amorphization, nano-crystallization, and inclusion of CdO₂ in CdS:O thin films obtained under oxygen partial pressure of 5%. The last films have shown significantly increased transmittance in a spectral range above the energy gap of CdS. The origin of this transmittance is discussed by taking into account redistribution of electronic density-of-states in amorphous phase, quantum size effect and contribution of CdO₂. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Eu_xCa_1–xGa₂S₄ is one of the phosphors with high luminescence quantum efficiency. It has high optical gain due to less concentration quenching for Eu centre. Production of EuGa₂S₄ film with smooth surface would lead to a possible construction of surface emitting lasers. We prepared films by sputtering with EuGa₂S₄ target. The EuGa₂S₄ films deposited on the substrates heated at 550–640 °C had the surfaces smoother than that of films post-annealed at 800–900 °C. The Eu₃Ga₅O₁₂ films were deposited on the substrates heated at 660–800 °C. The Eu₃Ga₅O₁₂ films, which were transparent and colourless, showed no photoluminescence and had smooth surfaces. The films were deposited on the cooled substrate for 30 min and sequentially deposited on the substrate heated at 640–700 °C for 10–30 min. The films, which consisted of two layers, EuGa₂S₄ and Eu₃Ga₅O₁₂, show high transmittances and exhibited yellow green emission. The films have the possibility to be applied to the laser. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Fundamental obstacles such as low production yields, non-reproducibility, and non-uniformity over large area are encountered in the commercialization of copper indium gallium (di) selenide (CIGS) solar cell. The precise control and manipulation of the thin film's local chemical compositional distribution during production is particularly difficult. In this paper, we develop a concept of metal organic (MO) sputtering using metal organic precursor in which the film compositions could be fine-tuned and tailored according to programmed intelligent material and device design. An essential feedback control of the film compositions using optical spectroscopy is crucial. Moreover, the addition of sulfur to enlarge the band gap of CIGS film is indispensable to improve the cell efficiency. We are also developing the chemical sulfurization technique, in which the sulfur and selenium atoms are interchanged in solution at room temperature and large band gap copper indium gallium sulfur-selenide (CIGSS) films can be obtained. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We investigated the magnetic properties of polycrystalline Co₃Sn₂S_2-xSe_x (0≤x ≤1.2) to ascertain the magnetism of the metallic ferromagnet Co₃Sn₂S₂. In Co₃Sn₂S_2-xSe_x, T_C and magnetization gradually decrease with increasing x, but there is no magnetic phase transition from ferromagnetic throughout the full range of composition. These results indicate that Se substitution effect on magnetism is small compared with In and Ni substitution. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Bulk electronic structures of covalent-chain antiferromagnets TlFeS₂ and TlFeSe₂ have been investigated by hard X-ray photoemission spectroscopy (HAXPES) and band calculations based on the full-potential linearized augmented plane wave method. Competition between localized and delocalized characters of Fe 3d electrons has been suggested by the slight discrepancies between valence-band HAXPES spectra and calculated density of states, as well as Fe 2p spectra with a broad charge-transfer satellite. It is assumed that this competition closely related to the crystallographic onedimensionality of these materials. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A laser system that can produce 0.4 J/10 ns/10 kHz-4 kW using a coherent beam combination with stimulated Brillouin scattering phase conjugate mirrors (SBS-PCMs) is proposed. The 4 kW coherent beam combination laser system consists of a front-end system, a pre-amplifier module, a coherent beam divider/combiner, and 4 main amplifier modules. The front-end system produces 1064 nm @ 10 kHz laser pulses, and it is amplified by the pre-amplifier. After the pre-amplifier module, the laser beam is divided into 4 sub-beams. Each sub-beam is amplified by the main amplifier module in a double-pass configuration and reflected by SBS-PCMs. Sub-beams are combined by a coherent beam combiner, and the output of the total system is designed to be 4 kW. With this 4 kW laser module, high-speed 2D holographic laser processing will be utilized. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present theoretical studies on the orientation control of micro-domains in anisotropic laser ceramics. The direction of the crystal axis that is parallel to easy magnetization in each micro-domain can be aligned along the direction of the applied magnetic field via two steps of fabrication processes. In the first step the alignment is performed during the slip-casting under the magnetic field, where directions of primary particles are forced to align along the direction of easy magnetization. However, even though rare-earth trivalent ions doped into primary particles as luminous ions enhance their magnetic moment, the perfect alignment control is not always possible due to Brownian fluctuations by slurry solvent at this stage. The further orientation control can be processed by the preferential grain growth, where an adequate orientation distribution of primary articles in the casted green body is required for the nearly perfect alignment in sintered ceramics. Therefore, it is important for further improvements of anisotropic laser ceramics to find the orientation distribution of primary particles in the slurry, which is determined by the ratio between the anisotropic magnetic potential and the thermal fluctuations. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Yb³⁺-doped Lu₃Al₅O₁₂ (Yb:LuAG) transparent ceramics were fabricated by vacuum sintering and hot isostatic pressing(HIP) method. TEOS and Sc₂O₃ were added as sintering aids by a high energy ball milling. Transparent nearly-fully dense samples with grain size of about tens of micrometers were obtained after 1820 °C sintering, while the grain size of HIP sample was only about several micrometers. The absorption spectra, emission spectra, and fluorescence life time of these transparent Yb:LuAG ceramics at room temperature have were measuredd. The absorption and emission cross-section of Yb:LuAG Ceramics at 937 nm and 1030 nm were 7.6×10^–21 and 23×10^–21cm² which are much higher than those of Yb:YAG crystal. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The distinctive features of the millimeter-wave sintering which make a method appealing for fabrication of optical ceramics are discussed. Among them are the absence of high temperature resistive heaters and the problem of their service life, favorable for elimination of porosity the inverse temperature distribution inherent in the volumetric microwave heating, highly uniform distribution of the millimeter-wave energy in applicators allowing for the sintering of large-size articles. This paper reports the results of the research on fabrication of optically transparent ceramics of compositions Nd:Y₂O₃, Yb:YAG, and Yb:(LaY)₂O₃ using a gyrotron-based set-up operating at frequency of 24 GHz. The green bodies of different compositions were compacted from powders produced by different methods: Nd:Y₂O₃ from the powder synthesized by laser evaporation of the target, Yb:YAG from a mixture of commercial powders, Yb:(LaY)₂O₃ from powder fabricated by self-propagating high-temperature synthesis. Laser oscillation was obtained from the sintered samples of all compositions. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A study on Laguerre-Gaussian (LG) modes selection in cw and pulsed Nd:YAG or Yb:YAG ceramic lasers pumped by diodes or an external laser source was carried out. Methods of scalar and vector LG modes selection from low to high orders, involving shaping of the pump profile, usage of intra-cavity lenses, uniaxial crystals and polarization selective mirrors, are considered. CCD camera images of beam profiles of hollow scalar LG_pm modes (p-radial, m-azimuth indices) of record high-orders and Bessel-like multi-ring modes with highly directional propagation properties are presented. CW and pulsed ceramic lasers with radially or azimuthally polarized LG vector modes of low and high orders are also demonstrated. Applications of the developed laser schemes and LG beams are discussed. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A variety of Er³⁺-, Tm³⁺-, and Yb³⁺-activated CaF₂-, SrF₂-, (Ca, Sr)F₂- and (Sr, Ba)F₂-based fluoride laser ceramics have been prepared by the hot-forming technique. Lasing of the SrF₂:Yb³⁺, (Ca, Sr)F₂:Er³⁺, (Ca, Sr)F₂:Tm³⁺, (Ba, Sr)F₂:Tm³⁺ and (Ba, Sr)F₂:Yb³⁺ specimens with diode pumping has been observed for the first time. Thermal conductivity data for the above fluorite-type laser materials are also presented and discussed. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study, a novel sequential electrodeposition of Cu-Zn-Sn-Se and Cu-Sn-Se layers was applied for fabrication of a Cu₂ZnSnSe₄ (CZTSe) thin film. The desired Cu-Zn-Sn-Se/Cu-Sn-Se bilayer was obtained at a selected applied potential from electrolytes containing corresponding metal and selenium ions. Annealing of the bilayer film under argon (Ar) flow induced significant losses of Sn and Se components due probably to evaporation of the SnSe compound. Suppression of these losses could be realized by introduction of Se vapor during the annealing: as a result, a CZTSe thin film with an ideal Cu-poor/Zn-rich composition for solar cell application was obtained. The solar cell with a device with the structure of glass/Mo/CZTSe/CdS/ZnO/AZO derived from thus-obtained CZTSe film exhibited a conversion efficiency of 1.1%, while the device still possessed a significant leakage current and a high series resistance. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu₂ZnSn(S,Se)₄ thin films were prepared by annealing the Cu/Sn/Zn precursors in sulfur/selenium mixing atmosphere. From EPMA analysis, the S/(S+Se) mole ratio in the thin films increased with increasing the S/(S+Se) mole ratio in the sealed ampoule. XRD study showed that the thin films had a kesterite phase in Cu₂ZnSn(S,Se)₄ and the a- and c-axis constants decreased with increasing the S/(S+Se) mole ratio in the thin films, following the usual linear Vegard behavior. Cu₂ZnSn(S,Se)₄ thin film solar cells annealed in S/Se atmosphere with an addition of Sn demonstrated V_oc=460 mV, I_sc=6.99 mA/cm² and V_oc=605 mV, I_sc=5.53 mA/cm². (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cu₂ZnSnSe₄ ingot was synthesized and then used as a precursor for selenization process in order to fabricate Cu₂ZnSnSe₄ thin films. The thin films were prepared at each point A-F in our selenization process and their properties were investigated. Cu₂ZnSnSe₄ ingot and thin films had a kesterite Cu₂ZnSnSe₄ structure. From EPMA analysis and XRD studies, the mechanism of Cu₂ZnSnSe₄ formation was discussed. Cu-Se phases were related to Cu₂ZnSnSe₄ formation. Cu₂ZnSnSe₄ may decompose to Sn-Se compound during the annealing process at 550 ^oC. Cu₂ZnSnSe₄ thin film solar cells demonstrated V_oc=300 mV, I_sc=7.25 mA/cm². The band gap energy of Cu₂ZnSnSe₄ thin film determined from the QE spectra estimated to be approximately 1.04 eV. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Electronic structures of orthorhombic and monoclinic Cu₄SnS₄, which exhibit a first-order phase transition at 232 K, are demonstrated based on the generalized gradient approximation (GGA) of the density functional theory (DFT). The calculated band gap was 0.39 eV for orthorhombic phase, while that was not obtained for monoclinic one. These calculated results confirm monoclinic phase has smaller activation energy (E_a) than orthorhombic phase. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

X-ray absorption spectroscopy investigation has been carried out at the Cu K edge on synthetic materials belonging to the ternary Cu-Sn-S system. In particular, Cu₃SnS₄ nanocrystalline powders, obtained through a solvothermal approach, and Cu₄SnS₄ microcrystalline powders, obtained through standard solid state reactions, were investigated.

From the XANES spectra, Cu is confirmed to be monovalent in both samples, thus implying a complex mechanism to achieve charge balance in Cu₃SnS₄. In this sample, the Cu-S EXAFS distance is found surprisingly short, and this suggests that Cu ions could be shifted outside the barycentre of the tetrahedra. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Uniformity of elements distribution in Cu₂ZnSnS₄ (CZTS) thin films were analyzed using X-ray photoelectron spectroscopy (XPS) to improve of conversion efficiency on solar cells. The films were prepared from CuCl or CuCl₂, ZnCl₂, SnCl₂, and thiourea by spray pyrolysis on quartz glass. The composition on surfaces of the as-grown CZTS films was Cu-poor and near stoichiometric compositions of Zn, Sn and S. In contrast to the surface, Cu-rich and Sn-poor compositions were obtained in the films. An existence of oxygen was observed on the film surface less than 20 nm. With increasing of thiourea concentration in the precursor, internal Cu composition, Cu/(Sn+Zn), was increased. S/metal ratio and Sn/Zn ratio in the films were less influenced by the thiourea concentration in the precursor solution. Cupper composition in the films was also affected a valence of Cu ion in the precursor. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

To produce highly transparent Yb-doped yttrium lanthanum oxide (Yb³⁺:(La_xY_1–x)₂O₃) ceramics two original technologies were used: laser synthesis of nanopowder and pulsed magnetic compacting. Sintering of the compacts in vacuum 3×10^–4 Pa at 1600–1700 °C during 13 hours led to transparent ceramics fabrication. The ceramics with relative density higher than 99.99% and grain size about 40 µm were fabricated. Full transmittance of 1.8 mm thick Yb_0,11La_0,23Y_1,66O₃ ceramics reaches 82.5%@800 nm. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical and mechanical properties of transparent ceramic MgAl₂O₄ spinel versus SPS conditions have been investigated. Syntheses kinetics of MgAl₂O₄ has been studied at different heating duration, pressure force. Behaviour of spinel transparency, density, elasto-plastic properties in depend on the mentioned terms has been studied. High transparency (72.6 % at wavelength of 555 nm) and high mechanical properties (fracture toughness of 2.4 MPa × m^1/2, microhardness of 18.52 GPa, Young's modulus of 212 GPa) have been achieved by decreasing the sintering duration and optimization of the pressing force. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Structural, optical and spectroscopic properties of Tm³⁺:Lu₂O₃ ceramics were studied. CW laser operation at 2068 nm with an output power of up to 34 W and a slope efficiency of 44% was obtained. Q-switched ocsilation with a pulse duration of 100-150 ns and a repetition rate of 1-10 kHz was achieved. Passive mode locking was achieved using an ion-implanted InGaAsSb quantum-well based SESAM or single graphene layer. Transform-limited pulses as short as 180 fs are generated at 2076 nm with an average output power of 400 mW and a pulse repetition frequency of 121.2 MHz. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Lutetium aluminum garnet (LuAG) is a garnet isostructure similar to yttrium aluminum garnet (YAG). High optical quality of 1.0 mol% Ho³⁺ doped LuAG transparent polycrystalline ceramics were fabricated successfully by reactive sintering method. The microstructures, optical properties and laser performance of the Ho:LuAG ceramics were investigated in this study. The in-line transmittance of Ho:LuAG transparent ceramics is higher than 84% at 2500 nm. The absorption coefficient of 1.0 mol% Ho:LuAG is 0.88 cm^–1 at 1906 nm and its absorption cross section is calculated to be 0.62×10^–20 cm². The laser oscillation of Ho:LuAG transparent ceramic without coated was also firstly obtained in this study. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A diode-pumped Yb:LuAG ceramics laser was investigated. CW laser performance was achieved. Passively femtosecond mode-locked laser operation was also successfully realized by using a SESAM mirror. The mode-locked pulse duration as short as 650 fs was obtained with a maximum output power of 200 mW. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Nd:YAG transparent ceramics with different doping concentrations were fabricated by a solid-state reaction method and vacuum sintering. Powder mixture of α-Al₂O₃, Y₂O₃, and Nd₂O₃ doped with tetraethoxysilane (TEOS) and MgO were sintered between 1500 _oC and 1750 _oC to examine the densification behavior in Nd:YAG ceramics. For the high doping 5 at%Nd:YAG transparent ceramics, the sintering kinetics and microstructure evolution were mainly discussed. It is found that the optimal sintering temperature for 5.0 at%Nd:YAG ceramics was at ∼1700 ^oC, and the in-line transmittance increased with the increase of holding time. The best specimen with the holding time of 30h achieved 82.2% in transmittance at 1064nm, whose average grain size was ∼15μm. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Transparent yttria ceramics were fabricated by sintering a mixture of 1 at.% Nd:Y₂O₃ and HfO₂ nanopowders produced by laser synthesis method. The best transmittance was 80.96% at the wavelength of λ=1080 nm in 6 mol.% HfO₂ doped sample (1.5 mm thick). The additives of hafnium broaden both pumping and luminescence bands of Nd₃₊ ion in yttria ceramics. The luminescence intensity of ₄F_3/2→₄I_11/2 transition was little affected by hafnium concentration. The effective lifetime of ⁴F_3/2 level in Nd:Y₂O₃ ceramics enhanced by 30% at 10 mol.% HfO₂ doping concentration and the decay kinetics of laser transition attains Förster's behavior. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The results of investigation of YSZ, Nd:Y₂O₃, Al₂O₃ nanopowder production by laser evaporation of oxide targets in a gas current are reported in present paper. For this purpose we used the pulse-periodical CO₂ laser and the continuous fiber ytterbium laser with 550 W and 600 W radiation mean power accordingly. The powders obtained by these lasers, consisted of weakly agglomerated spherical nanopartices (≥ 99 wt%), and ≤ 1 wt% of micron sized particles (drops and target fragments). Nanoparticles from various oxides produced by CO₂ laser in atmospheric pressure air had close average sizes (10÷16 nm). The productivity of nanopowder synthesis by CO₂ laser from YSZ 1%Nd:Y₂O₃, 1%Nd:Y₂O₃, Al₂O₃, and CeGdO was 23 g/hour, 29 g/hour, 24 g/hour and 80 g/hour, respectively. Unlike CO₂ laser the deep melting mode is realized during evaporation of 1%Nd:Y₂O₃ and Al₂O₃ targets by fiber laser. The crater depth increases up to 300–1000 μm in this mode. As a result, the target surface became very irregular and productivity of nanopowder synthesis was less, than in the case of CO₂ laser. To reduce the effect of deep melting the evaporation of a target has been investigated experimentally and theoretically. As a result of our investigations we have obtained 1%Nd:Y₂O₃ nanopowder with specific surface of 70 m²/g and productivity of 23 g/hour at air pressure 70 kPa. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Quantitative study of light elements such as carbon and oxygen in multi-crystalline silicon for solar cells is required to grow crystals with high quality. The transport of both carbon and oxygen is one of the critical issues to increase efficiency of solar cells made of silicon materials. Concentrations of carbon and oxygen in a furnace affect each others, therefore it is important to control mass transfer of carbon and oxygen in a furnace. Numerical calculation with a chemical reaction between carbon and oxygen was carried out to study how both light impurities are incorporated into crystals through the melt and gas during solidification process. The effects of flow rate and pressure on the impurities were examined. An increase in the flow rate can reduce both carbon and oxygen impurities in the crystal, though the reduction of carbon is more obvious. An increase in gas pressure can also obviously reduce the oxygen impurity but has only a small effect on the carbon impurity (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The present issue of physica status solidi contains papers presented at the 39th International Symposium on Compound Semiconductors (ISCS 2012) held in Santa Barbara on the UCSB campus, August 27–30, 2012. ISCS 2012 was colocated with the 24th International Conference on Indium Phosphide and Related Materials (IPRM 2012) during Compound Semiconductor Week (CSW 2012).

CSW 2012 was kicked-off with a joint plenary session. The four distinguished plenary speakers and the titles of their talks were William Deal, THz Integrated Circuits; John Geisz, III–V Semiconductors for High-efficiency Multijunction Photovoltaics; Andrew Shields, Semiconductor Devices for Quantum Information Applications; Marc A. Taubenblatt, Optical Interconnects for Computer-com. The opening session was followed by invited talks, contributed oral presentations, and poster presentations in both ISCS and IPRM. Also included in the technical program were two short courses and a rump session organized by IPRM.

The week also included an awards session, an excursion to downtown Santa Barbara with wine tasting and the conference barbeque on Goleta beach.

We extend our sincere thanks and appreciation to members of the Program Committees for their tireless efforts in assembling a high quality technical program and to members of the International Steering Committees and the UCSB Committee on Local Arrangements for their help. We also thank the exhibitors for their participation and support and gratefully acknowledge the support provided by the Office of Naval Research. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Nonparabolic nature of optical interband transitions of multi-quantum wells structure is important for related device designs. The optical interband transitions of In_0.53Ga_0.47As/In_0.52Al_0.48As MQWs including 20-nm-wide well clearly appeared on photocurrent spectra with polarized light source. The nonparabolic nature of conduction subbands was decided from experimental interband transitions. The electron effective mass smoothly increased from 0.041 m₀ to 0.07 m₀ in the conduction quantum well. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Low dark current photodiodes (PDs) in the short wavelength infrared (SWIR) region over 1.7 µm are expected to be used for many applications. InGaAs/GaAsSb type-II quantum well (QW) structures are considered to be attractive material systems for realizing low dark current PDs, owing to lattice-matching to InP substrates. In this report, we describe the successful operation of pin-PDs with InGaAs/GaAsSb QWs with InP capping layers grown by metal-organic vapor phase epitaxy (MOVPE). Distinct X-ray diffraction satellite peaks and emissions from type-II transition were observed. Electrical and optical characteristics of pin-PDs, such as dependence of responsivity on the number of QWs, were investigated. Dark current was 9.0 µA/cm² at 233 K and an external quantum efficiency (EQE) of 48% was obtained. These results indicate that it is possible to reduce the dark current of InGaAs/GaAsSb type-II PDs by using the InP capping layers grown by MOVPE. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the use of polarization sensitive photocurrent spectroscopy for identifying the participating transitions in type-II superlattices based on InAs/GaSb system. Prominent features in measured transverse magnetic and transverse electric photocurrent response on photodetectors have been analyzed to unambiguously predict the correct ordering of hole minibands as heavy and light hole minibands. Measurements carried out on both midwave infrared as well as long wave infrared superlattice detectors reveal the order of the participating valence minibands as: heavy-hole1, light-hole1and light-hole2, with the increasing energy. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A numerical model that accurately describes interband tunneling in backward diodes and broken-gap tunnel diode structures based on the InAs/GaSb material system is described. The model applies the transfer matrix method to discretized bias-dependent energy band profiles to calculate the transmission probability for tunneling. The model has been validated against experimental results, with good agreement in the current-voltage and curvature coefficient having been obtained for a range of hetero-structure backward diode and interband tunnel diode structures. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A sophisticated noise measurement setup employing a switching unit to measure statistically relevant numbers of InAs/GaSb superlattice photodiodes has been developed. The noise current resolution limit of 20 fA Hz^-1/2 enables the characterization of focal plane array-sized InAs/GaSb superlattice homojunction photodiodes for the long-wavelength infrared at 77 K. To resolve midwavelength infrared photodiodes a junction area of about (400 µm)² is required. Without switching unit and by using a dedicated low noise amplifier, noise currents down to 2 fA Hz^-1/2 can be achieved, allowing the noise characterization of mid-wavelength photodiodes with smaller junction areas. With this setup long-wavelength and mid-wavelength InAs/GaSb superlattice photodiodes, with generation-recombination limited dark current behavior, are investigated at 77 K. The measured diode noise follows the theoretically predicted shot noise level within the white noise part of the spectra. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the detailed radiometric characterization of the mid-wave infrared InAs/GaSb type-II strained layer superlattice detectors grown on GaSb (111) substrate. A red shift of 1.7 μm (at 295 K) was observed with respect to a similar detector grown on GaSb (100) substrate. We have measured, at 295 K and λ_{100% cut-off} = 5.6 μm, a dark current density of 0.53 A/cm² (at -50 mV) and a Johnson noise limited D* of 8.5 x 10⁹Jones, which are superior values to state-of-the-art T2SL detectors with the same (pin) design grown on conventional GaSb (100) substrates and operating in a similar wavelength range. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this paper we describe our recent experiments on coherent manipulation of electron spin states formed in a highly tunable GaAs/AlGaAs triple quantum dot device. The coherent evolution of spin states is achieved by using fast pulses from an initialization point in the (201) charge configuration region of the stability diagram. We demonstrate the versatility of the triple dot system capable of tuning to different regimes controlled by the width of the (111) region and pulse parameters. In particular we observe Δ'_1/2-Q_3/2 (analogue of S-T₊ in a double dot) and Δ'_1/2-Δ_1/2 exchange driven oscillations from both sides of the stability diagram involving all three spins. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We demonstrate photovoltaic operation of midwave (MW) quantum dot infrared photodetector (QDIP) with conventional n-i-n geometry, with a quantum cascade design. Quantum dot quantum cascade detector (QD-QCD) provides zero bias operation with responsivity of 10 mA/W and detectivity of 9×10⁹ cm.Hz^1/2W^-1 at 77 K for f/2 optics. Measured photoconductive gain is below 0.4, which is difficult to obtain with the traditional QDIP architecture, and is highly attractive for focal plane array applications. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Au-assisted growth of InAs NWs by MOVPE growth was investigated. We will discuss the NWs characteristics on GaAs and InP substrate with (111)B and (100) orientation, and on the V/III ratio during the growth. We have observed the growth direction of NWs on each substrates and confirmed that the surface diffusion have relation to the diameter of NWs. In the GaAs (111)B substrate, the diameter and length of NWs were depended on the local density of NWs. Furthermore, the tapered NWs were decreased by lowering the V/III ratio. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Intermediate band solar cells have attracted significant interest as a possible means of achieving high conversion efficiency. Under optimized growth parameters, we successfully achieve a high density of uniform InAs QDs grown on various matrixes by molecular beam epitaxy. Incorporating N atoms into GaAs and AlGaAs barriers effectively compensates the internal compressive strain and avoids formation of dislocations and defects. The 50 stacking of high density and uniform InAs QDs was demonstrated without detectable dislocations using 26 nm GaNAs as a barrier. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

InGaAs/InP DHBTs are fabricated using electron-beam lithography to define the emitter and base mesas. Emitter mesas 150 nm wide, and base mesas with < 25 nm misalignment to the emitter have been developed. Emitter contacts are prepared through blanket, refractory metal evaporation to obtain emitter contact resistivity ρ_ex = 2 Ω·µm². This low record resistivity, combined with the narrow emitter and base mesas, enables device RF performance of simultaneous f_τ and f_max of 530 GHz and 750 GHz, respectively, at a power density of > 40 mW/µm². (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report a method to control the shape of T-gates precisely by using multi-layer SiCN molds. The SiCN molds consist of a series of SiCN thin films with gradually changed etching properties. The SiCN was deposited by plasma-enhanced chemical vapor deposition using hexamethyldisilazane (HMDS) vapor. An optimized deposition condition of SiCN molds enables us to achieve more precisely control in the T-gate shape such as the stem angle. The SiCN molds technique was applied to the fabrication of T-gates in InGaAs high electron mobility transistors (HEMTs). Two types of HEMTs using the SiCN molds with different deposition conditions were fabricated. The detail analysis of the HEMTs indicates that the difference in the parasitic gate delay and gate resistance reflects the T-gate shapes. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present modeling of Sb-heterostructure backward tunneling diode (Sb-HBD) for high efficient millimeter- and submillimeter wave detection. The diode heterostructure is modeled and optimized using TCAD software implementing a non-local band-to-band tunneling model combining with the standard drift-diffusion model. The physical device model was found to be in good agreement with reported experimental results. InAsSb/AlSb/AlGaSb structures were proposed and simulated considering the material growth. The potential of the Sb-HBDs for high frequency operation applications is investigated. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have developed an ultrathin InP template with low defect density on SiO₂-Si and glass substrate by employing wet etching and wafer direct bonding technique. We have demonstrated epitaxial growth on these substrates and GaInAs/InP multiple quantum well layers were grown by low pressure metal-organic vapor-phase epitaxy. Photoluminescence measurements of the layers show that they are optically active and we have obtained almost the same intensity from these substrates compared to the InP substrate. These results may be attributed to improvement of InP template quality and should provide further improvements in device performance realized on SiO₂-Si and glass substrate. And, these are promising results in terms of integration of InP-based several functional optical devices on SiO₂-Si and glass substrate. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper describes the development of a heterojunction AlGaAs/GaAs PIN diode as a revolutionary improvement as compared to the homojunction GaAs PIN diode commonly used in microwave systems for commercial and military applications. In a heterojunction device the injected carriers from the junction are confined by the bandgap discontinuity between the AlGaAs/GaAs layers. This confinement effectively reduces the series resistance within the I-region of a PIN diode. Simulations of both single and double heterojunction PIN diodes predict a significant improvement in the return loss and insertion loss as compared to an equivalent GaAs PIN structure. In particular, the single heterojunction PIN diode, when simulated at a bias of 10 mA, indicates a factor of two reduction in high frequency insertion loss. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports AlGaN/GaN metal-insulator-semiconductor (MIS)-gate high electron mobility transistors (HEMTs) with a SiCN gate stack deposited by plasma-enhanced chemical vapour deposition (PECVD) using hexamethyldisilazane (HMDS) vapor. A transconductance of 69 mS/mm and a current gain cutoff frequency (f_T) of 25 GHz are obtained for the SiCN MIS-HEMTs with a gate length of 0.3 µm. These performances are better than those of the Schottky-gate reference devices. To clarify the origin of these improvements, we verified the cleaning effect of hydrogen used as a carrier gas for HMDS during the PECVD of SiCN. The results indicate that the hydrogen annealing improves the drain current density and f_T as well as it suppresses the current collapse. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The impacts of gate bias and device temperature on carrier energy distributions are reported for AlGaN/GaN High Electron Mobility Transistors. The lateral electric field and the average carrier energy are the highest at the end of gate on the gate-drain access side. The number of high energy carriers is the greatest in the semi-ON operating condition, with maximum energies exceeding the activation energy of defects in the AlGaN. There is a significant decrease in the number of very high energy carriers (greater than 2 eV) as the device temperature increases whereas the number of moderately energetic carriers (between 1 to 2 eV) is higher at elevated temperatures.(© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An important issue in multi-step epitaxial growth processes are the electrical characteristics of regrown interfaces. Here, we present a study on interface quality and its effect onto insulating behavior and scattering effects in planar transistors. A double heterostructure with an AlGaN/GaN high electron mobility transistor on top of an AlGaN back-barrier is used to assess electrical properties. Back-barrier templates were exposed to air for several days and subsequently treated by wet and dry chemical etching. A strong impact on leakage behaviour of the regrown interface was observed. Lateral leakage currents as low as 1x10^–8 A/mm are achieved with an optimized pre-treatment. Furthermore, under optimized conditions, the regrown GaN channel thickness is varied to investigate the effect of different distances between the two-dimensional electron gas (2DEG) and the regrown interface. Here, enhanced scattering mechanisms, probably due to ionized impurities, lead to a mobility drop of the 2DEG. A parasitic channel is observed, which indicates the presence of additional impurities at the regrown interface. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We have studied “gate-first process” in the fabrication of the Al₂O₃/AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) to improve the electrical properties of the MOSHFETs, where Al₂O₃ gate oxide is deposited before ohmic contact alloying. The interface state density of the Al₂O₃/GaN MOS diodes fabricated by the gate-first process was more than one order of magnitude smaller than that of the diodes fabricated by the conventional “gate-last process” where Al₂O₃ gate oxide was deposited after ohmic contact alloying. In addition, the saturation of the drain current at large gate voltages in the I_D-V_GS characteristics of the Al₂O₃/AlGaN/GaN MOSHFETs was relaxed and the maximum drain current was increased by employing the gate-first process. The hysteresis width of the I_D-V_GS curve of the MOSHFETs fabricated by the gate-first process was smaller than that of the devices fabricated by the gate-last process. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper investigated the effect of tensile strain in AlGaN barrier layer on the formation of micro-cracks at the surface of AlGaN/GaN HEMT structures. The Al_0.2Ga_0.8N/GaN HEMT structures were cooled down under N₂ + NH₃ and H₂ + NH₃ environments and high-density micro-cracks were found only for the latter case, indicating that hydrogen etching is essential for crack formation. On the other hand, no micro-cracks were observed even for H₂ + NH₃ cooling for thick AlGaN bulk layer. These results clearly correlate the tensile strain in the epitaxial layer and the formation of micro-cracks. Cross-sectional TEM analysis unveiled that screw/mixed dislocations were responsible for the formation of micro-cracks. It is believed that etching preferably starts from the dislocations and propagates along the crystal planes with the help of the tensile strain in the epitaxial layers. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Improvement in the internal quantum efficiency (IQE) of InGaN/GaN disks-in-nanowires by surface passivation is demonstrated. The highest IQE achieved through surface passivation for green emitting (λ=540 nm) InGaN/GaN disks-in-nanowires is ∼53%. Radiative and nonradiative carrier lifetimes are calculated for as-grown and surface passivated green emitting disks-in-nanowires. Passivated green sample exhibits a room temperature radiative lifetime of ∼748 ps, which is much smaller than that of equivalent quantum wells. Electroluminescence measurements on passivated green light emitting diodes containing InGaN disks demonstrate no roll over or efficiency droop up to 375 A/cm², and exhibit a blue-shift of 7 nm in peak wavelength. An enhancement in the light output due to surface passivation is observable in the relative external quantum efficiency of the surface passivated devices as compared with the as-grown samples. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Blue-emitting and green-emitting laser heterostructures were grown by molecular beam epitaxy, incorporating InGaN/GaN quantum dots as the active medium, with a measured quantum efficiency of 60% on n-GaN bulk substrates. These quantum dots exhibit no S-shape in the photoluminescence peak wavelength as a function of temperature, as typically found in comparable quantum well devices. The lasers were characterized by a threshold current density, J_th, of 930 A/cm² under pulsed bias, with a differential efficiency of 13.9%, and a wall plug (power conversion) efficiency of 0.4% at 1050 A/cm². Green-emitting quantum dot lasers have J_th = 935 A/cm². The lasers were also characterized by their modal properties through near field imaging (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We demonstrate MISFETs based on GaN p-epilayers with ion-implanted source/drain regions and atomic layer deposited (ALD) gate dielectrics of Al₂O₃ and HfO₂. The fabrication technology is similar to that used for silicon MOSFETs. We find that there are significant shifts (of order 1 V) in threshold voltage between FETs produced with Al₂O₃ and HfO₂ films, enabling depletion mode and enhancement mode device operation for the same substrate doping. The GaN MISFETs obtained maximum drain current of 580mA/mm and an extrinsic transconductance as high as 160 mS/mm. To the authors' knowledge, the transconductance achieved represents record performance for ion-implanted MISFETs of GaN without heterostructure barriers. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

InAlN/GaN high electron mobility transistor (HEMT) on Si substrate with a high breakdown voltage is reported. The observed off-state breakdown voltage was over 550 V and the specific on-state resistance was 0.7 mΩcm² in the fabricated device with the spacing between the gate and drain (L_gd) of 8 µm. After the measurement, the device was found not to be broken when it was observed by an optical microscope. The off-state breakdown voltage might be about 550 V in the device with L_gd of 5 µm, because the increase of the off-state leakage current was observed at the drain voltage of 550 V. If the off-state breakdown voltage was proportional to L_gd, the speculated off-state breakdown voltage from this result was 880 V in the device with L_gd of 8 µm. Therefore, InAlN/GaN HEMTs have potential for application as power electronics devices. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

This paper reports depletion-mode In_0.13Al_0.83Ga_0.04N/GaN high electron mobility transistors (HEMTs) on a SiC substrate with a record current gain cutoff frequency (f_T) of 317 GHz. Thanks to the combination of high electron mobility, regrown n⁺ InGaN/GaN ohmic contacts and scaled source-to-drain distance, the devices have an very low on-resistance of 0.4 Ω·mm. This very low resistance enables a significant reduction of the transistor parasitic delay and devices with a peak f_T of 317 GHz have been demonstrated for a 26 nm gate length. The device performance is limited by a relatively thick top barrier which causes serious short-channel effects (SCEs) in the devices with gate length below 50 nm. It is expected that a suppression of the SCEs will render further improvements in frequency performance in future devices. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present results from GaN-based high voltage transistors used for power switching applications. The static and dynamic properties of transistors on SiC and Si substrates are determined. Overall, this technology is capable to deliver 1000 V breakdown and 95 A output current as well as a lower product of on-resistance and gate charge than conventional Si-based structures. Areas of further improvement in epitaxial growth and device processing are outlined in order to combine these high currents and high voltages in a single device. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

M/A-COM Technology Solutions has continuing joint development efforts sponsored by the Department of Energy with MIT main campus and MIT Lincoln Laboratory to develop GaN on silicon two and three terminal high voltage/high current switching devices. The initial developmental goals were for a Schottky diode that has a reverse breakdown blocking voltage of >600 V and is capable of handling 10 A of forward current. A comparison of the M/A-COM Technology Solutions lateral GaN Schottky diode on-resistance as a function of reverse breakdown voltage for a number of both lateral and vertical GaN Schottky diode geometries taken from the literature is presented. The substrates employed for all of these data points are either sapphire, SiC, silicon, and even one study which utilized single crystal GaN. Also included in this plot are theoretical limits for the basic materials typically used in GaN Schottky diode construction. It can be seen that the reverse breakdown results of approximately 1500 V for M/A-COM Technology Solutions lateral anode connected field GaN Schottky diodes on silicon substrates compare extremely favorably with the reported performance of the state-of-the-art devices, regardless of substrate material or design geometry. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Enhancement mode GaN-based devices can be realised i.a. by gate recessing or the utilisation of a thin barrier. Yet, as this concept bases upon an increase in barrier capacitance, the application of a gate dielectric causing a capacitance reduction remains as a critical issue. A charge-free dielectric would shift the threshold voltage to negative values, eventually forming a depletion mode device. However, with an appropriate charge-containing dielectric, the same threshold voltage as for an HFET could be maintained. Here, a metal stack consisting of Al and Ti on top of a quaternary In_0.11Al_0.72Ga_0.17N barrier was plasma-oxidised and is shown to form insulated-gate devices with almost the same threshold voltage as their Schottky gate counterparts. The effects on the threshold voltage are discussed. It is shown that the transconductance improves by more than 80%, record drain current of 860 mA/mm is achieved and the dynamic behaviour dramatically improves. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

M/A-COM Technology Solutions has continued in the joint development efforts sponsored by the Department of Energy with MIT main campus and MIT Lincoln Labs to develop GaN on silicon three terminal high voltage/high current HEMT switching devices. The first year developmental goals were for a three terminal structure that has a reverse breakdown characteristic of >1200 V and is capable of switching 10 amperes of current. An average three terminal breakdown of 1322 V was achieved on a single finger 250 µm GaN on silicon HEMT device utilizing a source connected field plate with a 4.5 µm drain region overlap. An individual device breakdown on a single finger 250 µm GaN on silicon HEMT device with a SCFP of >1630 V was measured at a current of 250 µA (1mA/mm) – One of the highest yet reported for GaN on silicon in the industry. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

GaN-based heterostructure lateral Schottky barrier diodes (SBD) grown on Si(111) substrate are presented in this work. These SBDs own very low onset-voltage, V_F = 0.50 V, high reverse blocking V_BR > 600 V for L_AC > 8 µm, very low capacitive charge of 0.415 nC/A and a very fast recovery time of 6 ps extracted under large signal operation conditions. These unique qualities are achieved by combining lateral topology, AlGaN back-barrier epitaxial structure, fully recessed Schottky anode (ϕ_B = 0.62 eV) and anode field plate extension (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Photoexcited carrier dynamics and localization potentials in Al_0.86In_0.14N/GaN heterostructure have been examined by time-resolved photoluminescence (PL), transient photoreflectance and scanning near-field optical spectroscopy. The large GaN and AlInN PL intensity difference, and the short AlInN PL decay and GaN PL rise times indicate efficient photoexcited carrier transfer from AlInN to GaN via sub-band edge states. Near-field PL scans and photoreflectance data show that the diameter of the localization sites and the distance between them are well below 100 nm. Majority of these states is assigned to In clusters, in which the valence band has a higher energy than the valence band in a uniform AlInN alloy. It is likely that the carrier transport through the sub-band edge states proceeds via high conductivity channels involving extended defects. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

SiC polytypes in bulk form is systematically investigated using ab initio pseudopotential approach for the total energy calculations in four structures such as 3C (zinc blende), 6H, 4H, and 2H (wurtzite) structures with vacancy and nitrogen doping. Our calculated energy differences ΔE among four structures reveal that 3C and 4H are favorable for prefect SiC. The ΔE for SiC with vacancy suggests the most stable structures such as 6H with Si-vacancy and 4H with C-vacancy. The calculated vacancy formation energies suggest that C-rich condition prefers 6H whereas 4H is favored under Si-rich condition. Furthermore, nitrogen substituting for carbon and silicon respectively stabilizes 3C and 4H. These calculated results are consistent with experimental findings. The destabilization due to the vacancy formation and stabilization due to nitrogen of 3C-SiC are discussed by bond charge calculations and our simple formula of ΔE. It is found that vacancy formation inducing large deficit of bond charges favors 6H- and 4H-SiC and nitrogen-doping increasing bond charges stabilizes 3C-SiC. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Aluminum oxynitride (AlON), which is conventionally used as one of the ceramics with good thermal and chemical stability, has an attractive candidate for a tunable extreme UV luminous material due to its unique combination of properties and UV luminescence. In this paper, we have synthesized the novel AlON UV emitting materials, which have a wavelength from 4.29 to 4.54 eV, and discovered the core (AlON)-shell (Al₂O₃) like structures in a transmission electron microscopy. Furthermore, their potential application in a UV light emitter has been demonstrated by applying the combination with a CNT field emission cold cathode, which has been made by a simple printing method. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The growth process and morphology of three-dimensional GaSb islands grown on a Ga/Si(111)-√3 × √3 reconstructed surface have been studied by ultrahigh-vacuum scanning tunneling microscopy and non-contact atomic force microscopy. Faceted GaSb islands with a density of 10¹¹ cm⁻² are formed on Ga/Si(111) in multilayer growth at 350 °C. Hexagonal- and pyramid-shaped islands are formed at 400 °C. Dome-shaped islands, which are similar to the islands grown on clean Si(111), are only formed at 450 °C. The growth morphology of GaSb islands varies depending on the atomic species terminated on Si(111) and the growth temperature. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Electron-beam incidence-angle-resolved cathodoluminescence (IAR-CL) measurements on ZnO single crystals were demonstrated as an alternative way for the depth-resolved cathodoluminescence (CL) study by scanning acceleration voltage of the electron-beam. Incidence-angle dependent near-band-edge CL intensities were well reproduced by analyses considering a radiation pattern, an expansion of the electron-beam irradiation area, and an internal absorption factors. The quantitative agreement between the experimental and simulated results indicates that the IAR-CL technique is suitable for practical use in the depth-resolved CL study of device structures (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We proposed an indium-tin-oxide (ITO) based gas sensor which can operate at room temperature. ITO nano-crystal was screen printed on a quartz substrate. To improve the sensitivity and to decrease the resistivity of the printed ITO layer, pressurized annealing was adopted. Resistivity of the printed ITO gas sensor decreased from 3.5 kΩcm to 1.56 Ωcm by pressurized annealing. We could observe room temperature operation of the printed ITO gas sensor by using various gases such as Ar, N₂, O₂ and CH₄. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The interaction of cells with their microenvironment is an important factor, which influences phenotype, differentiation state and cell function. Interactions between cells and extracellular matrix (ECM) components are of crucial significance, especially for the development of electrical activity in neurons. For this study multi-electrode arrays were used to examine the influence of different substrates (glass, poly-D-lysine (PDL), PDL/laminin and laminin) on myenteric neurons during stimulation with lipopolysaccharide (LPS). The effect of LPS upon neurons grown on PDL/laminin resulted in an increased neuronal activity and calcium influx through L-type voltage gated calcium channels. Cultures on glass or PDL were not influenced. This demonstrates that the local microenvironment plays an essential role for the electrical potential of myenteric neurons.(© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Cell proliferation can be monitored by a wide range of well-established techniques. Most of the principles used rely on optical, single end-point methods, often involving the use of absorbent, fluorescent or luminescent compounds. These additives can interfere with the cell growth, thus producing distorted results. Electrochemical impedance spectroscopy provides a solution for this problem and enables continuous monitoring without interference. However equipment for this measurement technique is often bulky, highly expensive and lacks multichannel features. This paper presents a low-cost, compact hardware platform optimized for proliferation measurements, together with custom software to ease interpretation and physical modelling of data. Performance is demonstrated and measurement parameters are fine-tuned for three commonly used cell types in proliferation measurements. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)