• Issue
    Volume 218, Issue 17
    September 2021

Cover Picture

Free Access

Impact of Deposition Temperature on Crystal Structure and Ferroelectric Properties of (Al1−x Sc x )N Films Prepared by Sputtering Method

  • First Published: 08 September 2021
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Switchable Ferroelectric (Al1−xScx)N Films

In article number 2100302 by Hiroshi Funakubo and co-workers, the deposition temperature dependence of the crystal structure and ferroelectricity for Sc-doped AlN [(Al0.78Sc0.22)N] films is investigated. The background of the cover image is the XRD 2θ-Ψ mapping of AlScN films. Two crystal structures show polarization switching models of AlScN. P-E hysteresis response is ascertained for films deposited without heating substrates.

Masthead

Free Access

Masthead

  • First Published: 08 September 2021

Reviews

Recent Advances of Perovskite Solar Cells Embedded with Plasmonic Nanoparticles

  • First Published: 16 July 2021
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Herein, a synopsis of the effects of surface plasmon resonance in perovskite solar cells, including semitransparent and indoor perovskite photovoltaics, is provided. The working principle and the mechanisms underlying their improvement in light harvesting are also elucidated. Future studies can unravel promising pathways for the photovoltaic industry, particularly on semitransparent and indoor perovskite solar cells embedded with plasmonic nanoparticles.

Research Articles

Impact of Deposition Temperature on Crystal Structure and Ferroelectric Properties of (Al1−x Sc x )N Films Prepared by Sputtering Method

  • First Published: 01 July 2021
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(Al0.78Sc0.22)N films are deposited at various temperatures by the dual-source radio frequency (RF) magnetron sputtering method. The ferroelectricity is observed for all films deposited from 500 °C to ambient temperature without heating. The impact of the deposition temperature on the ferroelectric properties is discussed from the point of view of the thermal strain and the crystal structure.

Silicon Nanowire Solar Cells with μc-Si:H Absorbers for Radial Junction Devices

  • First Published: 26 June 2021
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A new energy conversion efficiency record of 4.13% under AM1.5G is obtained for silicon nanowire (NW) radial junction solar cells using hydrogenated microcrystalline silicon (μc-Si:H) as absorber material. This is achieved using 500 nm long NWs, n-type hydrogenated microcrystalline silicon oxide (μc-SiOx:H) contact layer and silver back reflector.

Open Access

Inkjet Printed Heating Elements Based on Nanoparticle Silver Ink with Adjustable Temperature Distribution for Flexible Applications

  • First Published: 25 June 2021
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This research has succeeded in developing bendable ultrathin fully inkjet printed heaters with homogeneous temperature distribution up to 120 °C and spot peak temperature up to 180 °C, controlled by input voltage and area coverage. Its functionality is demonstrated by a long-term test over several days with highest stability and endurance and only minor fluctuations in temperature and resistance.

Open Access

Analyses and Excess Oxygen Investigations by Scanning Transmission Electron Microscopy and Electron Energy Loss Spectroscopy at AlOx/Si Interfaces in Passivated Emitter and Rear Solar Cells

  • First Published: 14 July 2021
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The interface between silicon and the dielectric passivation layer is investigated by scanning transmission electron microscopy combined with electron energy loss spectroscopy at cross-sectional, lamellar samples prepared from the rear side of silicon solar cells. The acquired spectra of the interface region are evaluated regarding attribution of oxygen to the different phases, proving the presence of silicon oxide and excess oxygen.

The Effect of Nanometer-Scale V-Pit Layer on the Carrier Recombination Mechanisms and Efficiency Droop of GaN-Based Green Light-Emitting Diodes

  • First Published: 25 June 2021
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The effects of V-pits layer on the carrier recombination mechanisms and efficiency droop of GaN-based green light-emitting diodes are investigated. The V-pits layer can prevent the carriers from reaching dislocations and suppress nonradiative recombination. The V-pits layer can enhance hole injection into active layer and make the carriers evenly distributed in active layer. Therefore, Auger-related efficiency droop can be suppressed.

Open Access

Resonant Cavity–Enhanced Photodiodes for Spectroscopy of CH Bonds

  • First Published: 23 June 2021
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The spectral response from the optimized InAs-based resonant cavity-enhanced photodiode is closely matched to the absorption peak of methane. Wavelengths outside the peak do not cause a response and therefore other substances do not interfere with the measurement of methane. This spectral specificity is possible with carefully controlled layer thicknesses, that could be altered to target other substances.

Enhanced Efficiency of Tandem Organic Light-Emitting Diodes via Manipulating Heterojunction Composition of Charge Generation Unit

  • First Published: 30 June 2021
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The effect of various heterojunctions (HJs) of C60–CuPc as charge generation unit is investigated. When the ratio of bulk-HJ is optimal (C60:CuPc = 0.5:1), the performance of tandem device is best, which is mainly attributed to an increase in both C60–CuPc interfacial area and absorption in 0.5:1 C60:CuPc bulk-HJ.

Facilely Solution-Processed Lithium Carbonate for Tailoring Electron Injection in High-Performance Inverted Near-UV Organic Light-Emitting Diodes

  • First Published: 02 July 2021
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Robust electron injection layer of solution-processed Li2CO3 is demonstrated in inverted near-UV organic light-emitting diodes (OLEDs). The external quantum efficiency reaches 2.47% or 2.17% with 3 mg ml−1 Li2CO3 formic acid or 7 mg ml−1 Li2CO3 boric acid tailoring electron injection, which is comparable or even superior to a conventional normal-structured device with PBD as emissive molecule.

AC/DC Magnetic Field Sensing Utilizing Mechanically Mediated Product Effect of Ampere Force Caused by Eddy Currents and Piezoelectricity in a Magnetoelectric Disk

  • First Published: 02 June 2021
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Herein, the magnetoelectric coupling effect originating from the mechanically mediated product effect of piezoelectric effect and ampere force effect caused by the eddy current under the action of AC and DC magnetic fields in a metallic/polymeric laminated disk is investigated with the purpose of achieving AC/DC magnetic field sensing using physical transduction principles.

Special Section: Progress and Perspectives in Functional Materials Guest-Edited by Albena Paskaleva, Hassan Chamati, and Julia Genova

Free Access

Topological Defects in Nematic Liquid Crystals: Laboratory of Fundamental Physics

  • First Published: 08 September 2021
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Topological Defects

The curvature of a closed manifold exhibiting orientational order has a strong impact on positions and the number of topological defects (TDs). The surface integrated Gaussian curvature determines the total winding number of TDs within the manifold. If a region possessing a large enough negative Gaussian curvature is introduced it can trigger pairs {defect, antidefect}, possessing opposite signs of the winding number. More details can be found in article number 2000752 by Mitja Kralj, Marko Kralj, and Samo Kralj.

Guest Editorials

Free Access

Progress and Perspectives in Functional Materials

  • First Published: 08 September 2021

Feature Articles

Spatially Resolved Optical Characterization of Functional Materials Using Coherence Scanning Interferometry

  • First Published: 24 February 2021
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The technique of local spectroscopy using white light interference microscopy for characterizing functionalized materials is reviewed. Experimental and simulated results of spatially resolved reflectance spectra are given on different kinds of materials. The technique is extended to the local measurements of refractive index and thickness of transparent layers and to individual spherical particles buried in transparent and scattering layers with a priori information.

Reviews

Topological Defects in Nematic Liquid Crystals: Laboratory of Fundamental Physics

  • First Published: 14 January 2021
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Topological defects (TDs) appear in all branches of physics due to the simplicity of generic mechanisms. Nematic liquid crystals (NLCs) represent an ideal testbed for their study. In them, TDs can be relatively easily created, controlled, and observed, which enables a detailed and controlled analysis of their physical properties. Furthermore, TDs in NLCs can be exploited in diverse applications.

Original Papers

Thermally Stabilized Soot for Supercapacitors

  • First Published: 06 March 2021
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Chimney soot is used as an electrode material for supercapacitance applications. The research presents physical investigations and an attempt for implementation of waste carbon material (soot) in supercapacitor (SC) prototypes. This work is driven by the idea of circular economy and the possibility of using such materials without expensive treatment in future technologies.

Optical Properties of ZnO Deposited by Atomic Layer Deposition on Sapphire: A Comparison of Thin and Thick Films

  • First Published: 19 December 2020
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Designing an optoelectronic device based on ZnO film requires one to account for the coupling between the growth temperature, film thickness, and the physics of electrical charge transport in the film. The results presented here demonstrate that the intrinsic direct gap of ZnO film depends upon applied growth temperature rather than the film thickness when Burstein–Moss corrections are made.

Open Access

Exploring the Interface Landscape of Noble Metals on Epitaxial Graphene

  • First Published: 24 April 2021
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A comparative study on the interaction between noble metals (NMs) and epitaxial graphene is presented. Combined Raman studies, DFT calculations, and supervised classification methods provide better understanding on the nature of NMs effect on phonon dispersion of graphene. A robust model to classify Raman data of metal-decorated epitaxial graphene is developed based on principal component analysis and linear discrimination analysis.

Structural Characterization of Oxyhalide Materials for Solid-State Batteries

  • First Published: 17 February 2021
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Novel Ca-, Ba-, and Mg-doped Li3OCl, Na3OCl, and K3OCl oxyhalides are synthesized. The formation of antiperovskite Li3OCl is verified by X-ray diffractometry. Raman spectra show that the samples absorb water. The first- and second-neighbor distances can be identified for Ca-doped samples, approving the short-range order. Transmission electron microscopy indicates that the samples exhibit structural and compositional inhomogeneities on the nano scale.

Atomic Layer Deposition of AlN on Graphene

  • First Published: 22 June 2021
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A comparative study on elemental surface composition (X-ray photoelectron spectroscopy (XPS)) and surface morphology (scanning electron microscopy (SEM)) of AlN thin layers using atomic layer deposition (ALD) approach on graphene and on the 4H-SiC substrate is presented. XPS and SEM show that deposition on graphene results in a lower surface coverage, highlighting the challenge for growth of 2D AlN.