Monolayer Mo1−x−yRexWyS2‐Based Photodetectors Grown by Chemical Vapor Deposition

The utilization of alloyed 2D transition metal dichalcogenides (TMDs) has become a pivotal approach for addressing challenges in material applications. The judicious selection of dopant constituents offers a potent means to finely modulate the materials' bandgap, consequently broadening the potential applications of 2D materials. In the context of an investigation, Mo1−x−yRexWyS2 is successfully synthesized using chemical vapor deposition. With a bandgap of 1.33 eV, this material exhibits promising prospects for application in the realm of optoelectronics. This advancement enables the fabrication of the Mo1−x−yRexWyS2 photodetector. The rigorous testing and analysis of photoelectric performance reveal significant improvements in both responsivity and response speed compared to analogous detectors. This accomplishment not only furnishes a novel paradigm for the advancement of photodetectors but also contributes fresh insights to the domain of alloyed 2D TMDs.


Introduction
[3] Despite its impressive electrical and thermal conductivity, the characteristic of zero bandgap restricts its potential in the semiconductor realm.[15] Molybdenum disulfide (MoS 2 ) is a prominent TMD.Sulfur (S) and molybdenum (Mo) elements combine to form a layered sandwich structure denoted as S─Mo─S.It is characterized by robust intra-layer chemical bonds and relatively weak interlayer van der Waals forces, resulting in a stable intra-layer structure and fragile interlayer connections, allowing facile exfoliation (similar TMDs include WS 2 , ReS 2 , WS 2 , and MoSe 2 ). [16,17]Its bandgap, influenced by layer count, decreases from 1.8 eV for single-layer MoS 2 to ≈0.8 eV in bulk MoS 2 . [18]MoS 2 's favorable characteristics, including high carrier mobility and stability, make it versatile for applications in electronic components like photodetectors and metal oxide semiconductor field effect transistors (MOSFETs). [19]Currently, based on MoS 2 , exploration has expanded to ternary (Mo 1−x Re x S 2 , [20] Mo 1−x W x S 2 , [21] MoS 2(1−x) Se 2x ) [22] and quaternary variants (Mo x W (1−x) S 2y Se 2(1−y) ). [23]The notable electrical conductivity and thermal stability of these materials make them suitable for a variety of application contexts.
Nevertheless, certain limitations characterize 2D molybdenum disulfide, with defects within its layered structure emerging as a paramount concern. [24]Such defects encompass vacancies, impurities, and assorted structurally anomalous regions. [25,26]hese deviations wield substantial influence over the physical, chemical, and electrical traits of 2D molybdenum disulfide.Notably, they disrupt electron transport pathways, thereby imparting alterations to their electrical attributes.Furthermore, defects exert discernible effects on the material's optical absorption and emission characteristics, thereby casting an impact on its photoelectric performance.Practical applications also confront hurdles necessitating resolution such as augmenting carrier mobility and conductivity.Therefore, comprehensive exploration remains imperative regarding the stability and endurance of molybdenum sulfide, ensuring its sustained effectiveness and dependability throughout prolonged usage. [27,28]][35][36] These impurity elements encompass diverse metal ions, non-metal ions, and even rare earth elements. [37,38][52] For instance, researchers harnessed the CVD approach to infuse rhenium into MoS 2 , which improved the responsiveness of the photodetector. [53]Others adopted ion implantation to introduce tungsten (W) for high-speed detector fabrication, [21,54,55] while some introduced niobium (Nb) for crafting high-performance transistors. [56]Additionally, the incorporation of the non-metallic element nitrogen (N) aimed to enhance light absorption and bolster photoelectric conversion efficiency. [57]By judiciously selecting doping constituents, regulating doping concentration and distribution, synergizing with other modification methodologies, and refining fabrication processes, the photoelectric capabilities of MoS 2 can experience further enhancements. [58]Such advancements expand the realm of possibilities for employing MoS 2 in photovoltaic conversion and optoelectronic devices. [59]n this work, monolayer Mo 1−x−y Re x W y S 2 films were synthesized by the CVD method using a certain proportion of sulfur, MoO 3 , WO 3 , and ReO 3 powders in a high temperature, and then Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis of the resulting alloy materials were performed.In order to further study the optoelectronic properties of the synthesized Mo 1−x−y Re x W y S 2 , the structure of the quaternary material was simulated, the change of the band gap was calculated, and then a photodetector based on the Mo 1−x−y Re x W y S 2 was fabricated, which achieved high performance.

Result and Discussion
Mo 1−x−y Re x W y S 2 flakes were synthesized through the CVD technique, as illustrated in Figure 1a (for a detailed procedure, refer to the Experimental Section).In the growth dynamics of 2D materials via CVD, three crucial physical parameters come into play: adatom diffusion on the substrate, edge kinetics, and precursor flux. [60]These factors collectively govern the growth process and the resulting properties of the synthesized material.In Figure 1b, four distinct reaction steps illustrate the synthesis process.A constant amount of oxide is maintained while the deposition temperature is altered during the oxide deposition step.Excess oxide molecules are carried away from the reaction zone by the Ar carrier gas, ensuring a constant oxide deposition after the process.As for sulfur, it transforms into the gas phase at higher temperatures and is then driven to the reaction zone by the carrier gas, where it reacts with the oxide molecules adsorbed on the substrate, leading to the formation of the new material.This research maintained a constant precursor concentration while varying the growth temperature.Optical images in Figure S2a-h, Supporting Information, display the samples grown at 800, 850, 900, and 950 °C, respectively, exhibiting distinct morphologies.It is evident from the optical images that the grown Mo 1−x−y Re x W y S 2 material exhibits superior morphology at a growth temperature of 900 °C.Raman spectra of Re 0.15 W 0.05 Mo 0.80 S 2 film grown by CVD under different temperatures (800, 850, 900, and 950 °C) in Figure S3a,b, Supporting Information.At 900 °C, the FWHM of A 1g and E 1 2g peaks are minimized, indicating that the material grown at this temperature has fewer defects and is more stable.In Figure 1c,d, the optical image and high-magnification atomic force microscope (AFM) image of the monolayer Mo 1−x−y Re x W y S 2 (as-grown sample at 900 °C) are presented.The surface roughness of the material was analyzed using high-magnification AFM images, revealing a roughness value of R a = 0.251 nm.To further investigate the growth effects, a cross-sectional transmission electron microscope (TEM) image of the film on the Si/SiO 2 substrate is shown in Figure 1e, confirming that Mo 1−x−y Re x W y S 2 is a monolayer with a thickness of ≈0.54 nm.For further verification of the elemental composition in the Mo 1−x−y Re x W y S 2 film, energy-dispersive X-ray (EDX) mapping was conducted.The EDX mapping results, shown in Figure 1f-i, reveal the distribution of the four elements Mo, Re, W, and S in the film.Mo, Re, W, and S are represented by orange, purple, red, and gray, respectively.It is evident that the distribution of these elements in the synthesized film is not uniform, and the figure shows the spatial segregation of various elements.
To conduct a more in-depth analysis of the material composition, Raman spectroscopy was utilized to study the composition of the alloy that was produced and also create spatial maps of specific Raman vibrational modes.In Figure 2a, the grown state sample the grown state sample exhibits two distinct peaks, E 1 2g and A 1g , with A 1g doping causing a red-shifted peak position toward the long wave direction.This red-shift is attributed to the homogeneous alloying of Mo-W-Re and changes in vibrational modes after doping.Additionally, the E 1 2g peak becomes higher compared to the A 1g peak, indicating an increase in electron concentration.The combined changes of A 1g and E 1 2g suggest that Re doping introduces a significant number of electrons.According to literature, Re doping causes a red shift in the peak position, while W doping causes a blue shift.However, in this experiment, the peak position is red-shifted, and the height difference between E 1 2g and A 1g becomes smaller, though not exceeding A 1g .This suggests that both Re and W are involved in regulating the synthesis process, with Re doping having a more significant impact than W doping. Figure 2c,d represents Raman mapping of the specific area indicated in Figure 2b.Based on the Raman mapping shown in Figure 2c,d, it is evident that there is a slight deviation from compositional homogeneity at the two Raman peaks.This phenomenon can be attributed to the alteration in the composition of MoS 2 due to doping and the possible presence of small amounts of defects in the Mo 1−x−y Re x W y S 2 .However, there were no significant compositional differences observed in the Raman mapping, indicating a high degree of alloying and material stability in the doped material.To assess Mo 1−x−y Re x W y S 2 's stability, Raman peak level tests were performed during a temperature change from 300 to 400 K, as shown in Figure 2e.The change in peak position is attributed to the thermal expansion of Mo 1−x−y Re x W y S 2 resulting from an increase in temperature.Furthermore, the incorporation of impurity atoms induces changes in the structure of MoS 2 , leading to a higher first-order temperature coefficient compared to the pristine material.At this point, the Mo 1−x−y Re x W y S 2 's entropy increases, enhancing its stability.Despite these alterations, they do not significantly affect the thermal stability of Mo 1−x−y Re x W y S 2 .Therefore, it can be concluded that this material exhibits outstanding thermal stability.
XPS measurements were conducted to investigate the influence of W and Re ions in MoS 2 .The XPS analysis confirmed the precise composition of each alloy sample and preliminarily analyzed their electronic structure (Figure 2f-i).Figure 2f- The 3D image of Figure 3a illustrates an inhomogeneous doping pattern of Re with W elements, mainly doped by replacing the position of Mo atoms.To investigate the intricate atomic distribution of elements in this complex quaternary 2D system, the 900 °C as-grown samples are examined using a Nion aberrationcorrected Ultra STEM 100, operating with an accelerating voltage of 120 kV. Figure 3b presents a typical atomic-resolution scanning transmission electron microscopy with an annular darkfield (STEM-ADF) image of a monolayer x W y Mo 1−x−y S 2 flake, exhibiting the characteristic 2H structure.The 2H polymorphism is further verified by the corresponding fast Fourier transform (FFT) pattern (Figure 3c), which reveals a perfect hexagonal lattice.The lattice constant of 2H-Re 0.15 W 0.05 Mo 0.80 S 2 is measured at ≈3.2 Å (Figure 3d), which greatly resembles the pristine 2H-MoS 2 .Distinguishing the metal site from the chalcogenide site can be achieved by analyzing a histogram of the intensities associated with each of these distinct sites.This histogram will help in characterizing and differentiating the relative abundance or concentration of these sites within the material.Figure 3d,e   To determine the synthesis and bandgap characteristics of the new-obtained sample, we performed first-principles calculations of the formation energy and bandgap changes.As shown in Figure 4a, the formation energy of the W-doping and Re-doping defects are presented under S-poor and S-rich conditions.Under S-poor conditions, the formation energies for both Re and W doping defects are high, indicating that doping is difficult to achieve.However, under S-rich conditions, the formation energies decrease dramatically, indicating that doping becomes energetically favorable and the formation of the doped material could be promoted.Additionally, when in a high concentration of S carrier gas, it can be observed that the formation energy of Re doping is significantly lower than that of W doping.Therefore, the feature of formation energies is consistent with the experimental results and explains the higher doping of Re in the sample.
Figure 4b shows the varied DOS after Re and W co-doping compared to the undoped MoS 2. The Re-W co-doped MoS 2 exhibits n-type doping with the Fermi level crossing the conduction band minimum (CBM), which is consistent with the experimental results indicating that Re doping introduces electrons into the material.Additionally, Figures 4c,d show the intrinsic band structure and the unfolded band structure of the co-doped structure, respectively, where the bandgap values are clearly represented.The intrinsic MoS 2 shows a direct bandgap of 1.66 eV.However, after doping with Re and W, the bandgap decreases to 1.33 eV and maintains the direct bandgap feature.Additionally, the band structure of the co-doped MoS 2 is observed to be n-type doping, indicating the introduction of more electrons into the material.
Therefore, Re and W doping can be used to effectively control the bandgap of MoS 2 .
In recent years, 2D TMDs have exhibited remarkable photoelectric conversion properties, particularly in photodetector applications.To investigate the photoelectric characteristics of the recently synthesized Mo 1−x−y Re x W y S 2 material, Mo 1−x−y Re x W y S 2 photodetectors were fabricated on n-Si/SiO 2 , as depicted in Figure 5a.Employing electron beam lithography (EBL) equipment, we designed finger electrodes with narrower trench spacing to optimize their optoelectronic performance.This strategic use of fork-finger electrodes simultaneously enhances the photodetector's effective area, further amplifying its optoelectronic capabilities.The photodetector's photoelectric properties were subsequently tested at a bias voltage of 1 V.The initial assessment involved measuring the dark current (I dark ) under dark conditions, revealing a dark current magnitude of ≈1 μA at 1 V bias.This observation signifies the presence of uninhibited electron flow within the material, a quality that is also advantageous for field-effect transistor (FET) studies.Upon irradiation with a 365 nm laser, the photodetector's photoelectric response was evaluated at 10% intervals starting from 100%, as indicated in Figure 5b.The results illustrate a noteworthy order of magnitude increase in photocurrent relative to the dark current subsequent to laser irradiation.This disparity in current at a 1 V bias voltage is striking.The laser's effect lies in its ability to excite additional free electrons within the material, a phenomenon facilitated by the substantial influx of electrons due to the doping of Re, W atoms. [20] Consequently, this leads to an elevation in photocurrent attributed to the augmented population of excited electrons.Furthermore, the enhancement in photocurrent also exhibits a minor hole contribution, stemming from the presence of molybdenum vacancies evident in TEM images.These findings collectively underscore the intricate interplay of doping and material vacancies, contributing to the observed photoelectric improvements.
Subsequently, the curve of the detector current versus time (I-V, t) was evaluated under a bias voltage of 1 V and a light intensity of 365 nm, as depicted in Figure 5c.The photodetector's response exhibited notable acceleration in the presence of the 365 nm light intensity.To gain a closer perspective, a local zoom-in analysis was performed, as presented in Figure 5d.Response time is usually defined as the time taken by 10% to 90% of the net photocurrent.From the localized zoom of Figure 5d, it is evident that both the rise time and fall time of the material amount to 0.160 s, reflecting a substantial improvement in comparison to the response time of MoS 2 .This marked enhancement can be attributed primarily to the synergistic doping of rhenium and tungsten, which contributes to the partial filling of vacancies generated during the growth process.The presence of vacancies within the material results in the confinement of free electrons, generating an electron-trapping effect.This effect extends the lifetime of carriers, thereby enhancing optical responsivity.However, it introduces a critical drawback for detectors reliant on responsiveness. [21,55]Consequently, a reduction in vacancies directly translates to a shorter carrier lifetime, facilitating a swifter response and consequently a higher-speed performance.Collectively, by comparison with other TMDCs photodetectors (refer to Figure S4, Supporting Information), the comprehensive test outcomes underscore that the incorporation of rhenium and tungsten co-doping in MoS 2 yields dual benefits: it improves the responsivity while significantly increasing the speed of response.
Conclusively, the assessment of the photodetector's efficacy is conducted through pertinent parameters, graphically depicted in Figure 5e,f.A pivotal measure of its photoconversion attributes is the responsivity (R), calculated as R = I ph /(P in S).Here, I ph signifies the photocurrent, S denotes the effective illuminated area of the heterojunction plane, and P in represents the incident light's power density.The quantification of the photodetector's detection prowess is encapsulated by the noise equivalent power (NEP) and the specific detection rate (D*).Superior detection capability corresponds to lower NEP and higher D* values.The evaluation of NEP and D* can be executed employing the following equations: NEP = (2qI dark Δf) 1/2 /R and D* = A 1/2 /NEP.Within these expressions, I dark characterizes the dark-state current, Δf signifies the bandwidth (set at 1 in this instance), and A pertains to the active device area.Notably, the calculated active area (A) stands at 506 μm 2 , referencing the face-to-face region of the two electrodes.Remarkably, as depicted in the figures, the responsivity diminishes with escalating optical power.This phenomenon arises from the saturation of photoelectron absorption at low optical power levels, leading to a plateau in responsivity despite increased light intensity.This observation underscores the photodetectors' sustained excellence even under conditions of subdued light.It exhibits an exceptionally heightened sensitivity, manifested by NEP values as diminutive as 1.28 × 10 −15 W Hz −1/2 , and an extraordinary detection capability, evidenced by D* values reaching up to 1.76 × 10 10 Jones.

Conclusion
In summary, we have successfully synthesized a novel quaternary material (Re 0.15 W 0.05 Mo 0.80 S 2 ) by incorporating rhenium and tungsten into molybdenum sulfide through a doping process.Various characterization techniques were used to verify the presence and composition of each element in the new material.Additionally, utilizing STEM-ADF imaging, confirmed the stable 2H phase structure of the single-layer material.Through density functional theory (DFT) calculations, it investigated the variation in the band gap of Re 0.15 W 0.05 Mo 0.80 S 2 and conducted a comprehensive analysis to elucidate the underlying reasons for these changes.Importantly, Re 0.15 W 0.05 Mo 0.80 S 2 displayed exceptional photoelectric properties even under ambient conditions, exhibiting a remarkable responsivity of 405.97A W − ¹ and an impressively rapid response time of 0.160 s.Comparative assessment with similar photoelectric detectors underscored the substantial advancements of our material, showcasing substantial enhancements in both response rate and response speed.This research opens up novel avenues for the development of TMDs, leveraging tailored content ratios of distinct elements to explore innovative possibilities in the field.

Experimental Section
Material Synthesis: The monolayer Mo 1−x−y Re x W y S 2 (0.54 nm) was epitaxially grown on Si/SiO 2 substrates using the CVD method (SK-G05123K-3-655, TIANJIN ZHONGHUAN FURNACE Corp., China).Sulfur powder (1.40 g) was placed in the alumina combustion boat upstream of the quartz tubular furnace.Molybdenum trioxide powder (MoO 3 , 99.95%), tungsten trioxide powder (WO 3 , 99.95%), and rhenium trioxide powder (ReO 3 , 99.95%) were evenly dispersed in the alumina crucible and placed in the center of the furnace.Then, cleaned Si/SiO 2 substrates (1 cm × 1 cm) were placed directly on top of the MoO 3 , WO 3 , and ReO 3 powder in the alumina crucible boat.After the position was fixed, repeated pumping cycles were carried out to remove impurity gases in the furnace tube, and the reaction was further continued under optimized conditions in an Ar ambient.After the reaction, the furnace was naturally cooled to room temperature under 120 sccm of Ar.
Characterization Methods: Raman spectroscopy was performed using the Confocal Renishaw system (512 nm, 0.25 mW).Cross-sectional samples were prepared by FIB (FEI-G4) to directly observe the vertical morphology.TEM testing was conducted using the America FEI-Titan Cubed Themis G2 300, and energy disperse spectroscopy (EDS) analysis was performed using its related equipment.Topography and surface potential images were measured using a Bruker ICON AFM in Scanasyst mode.
DFT Simulations: All the calculations were performed based on the projector-augmented wave (PAW) method as implemented in the Vienna ab-initio simulation package (VASP).The general gradient approximation with the exchange and correlation interaction of Perdew-Burke-Ernzerhof (GGA-PBE) was adopted to optimize the system geometry.The cutoff energy of the plane-wave basis was set to be 500 eV.The lattice and atomic positions were fully relaxed based on the conjugate gradient algorithm until the Hellmann-Feynman forces were less than 0.01 eV Å −1 , and the total energy convergence criterion was set to be 10 −5 eV.The Brillouin zone (BZ) was represented by Gamma-centered unit cells with 3 × 4 × 1 Monkhorst-Pack k-point mesh for geometry optimizations.In order to eliminate the periodic image interaction, a vacuum layer of 20 Å was constructed perpendicular to the layer plane.
The formation energy of a neutral doping defect is computed from where E Mo and E X are the energy of one atom of the bulk metal Mo and (X = Re, W); E MoS 2 is the total energy of MoS 2 and E doping is the total energy of MoS 2 with the dopant on a Mo lattice site.Fabrication and Measurement of the Devices: The Si/SiO 2 substrate underwent a pre-cleaning process, which included 10 min of acetone, 10 min of isopropanol, and 10 min of deionized water ultrasonic cleaning steps to remove residues.Then, the Re 0.15 W 0.05 Mo 0.80 S 2 thin film layer was grown on the cleaned substrate by the CVD method.Finally, Cr/Au (5 nm/50 nm) was deposited to form the anode.The electrical and optical performance of photodetectors, including I-V characteristics and I-T characteristics, was measured using a Keithley 4200-SCS semiconductor analyzer on a probe station.To describe the electrical characteristics of the fabricated Re 0.15 W 0.05 Mo 0.80 S 2 diode, I-V measurements were performed in the ±1 V range.

Figure 1 .
Figure 1.a) Schematic of growth procedure for quaternary alloys.b) I,II) Illustration of MoO 3 /ReO 3 /WO 3 deposition step.III,IV) Illustration of Mo 1−x−y Re x W y S 2 growth step.c) Optical image of as-grown triangular monolayer quaternary alloys (size = 60 um).d) AFM images of monolayer Mo 1−x−y Re x W y S 2 grown at 900 °C.e) Cross-sectional projection electron microscopy image of Mo 1−x−y Re x W y S 2 on Si/SiO 2 substrate (TEM).f-i) Energy-dispersive X-ray (EDX) mapping of the four elements of Re, Mo, W, and S. Scale bars: (f-i) 8 nm.

Figure 2 .
Figure 2. a) Raman spectroscopy of the pure MoS 2 and the W, Re-doped MoS 2 .b-d) Raman mapping of alloys grown at 900 °C (from the selection in figure b).e) The Raman shift of E 1 2g and A 1g as a function for temperature, including the value of  obtained from linear fitting.f-i) XPS spectrum of f) Mo 3d peaks and g) S 2p peaks in W-doped MoS 2 and pure MoS 2 , h) W 4f peaks in W, Re-doped MoS 2 .i) Re 4f peaks in W, Re-doped MoS 2 .

Figure 3 .
Figure 3. a) 3D schematic and master view of the Mo 1−x−y Re x W y S 2 .b) High-resolution STEM image of monolayer as grown sample at 900 °C.c) The selected area electron diffraction (SAED) pattern.d) Enlarged view of the red selection in (b).e) Intensity profile of the material.Re and W atoms are identified by the intensity profile.
i shows the Mo 3d peaks and S 2p peaks of W, Re-doped and pure MoS 2 , W 4f peaks, and Re 4f peaks of W, Re-doped MoS 2 .Previous research indicates that W introduces hole features in MoS 2 .In Figure2f, it is observed that red-shifts in the binding energy characteristic peaks of Mo 3d and blue-shifts in the binding energy characteristic peaks of S 2p after Re and W-doping.Specifically, Mo 3d 3/2 shifts from 233.08 to 232.93 eV, and Mo 3d 5/2 shifts from 229.91 to 229.71 eV.Additionally, S 2p 1/2 shifts from 163.99 to 164.07 eV, S 2p 3/2 + 2p 1/2 shifts from 162.78 to 162.82 eV, S 2p 3/2 shifts from 161.25 to 161.58 eV, respectively (Figure2g).In Figure2h,i, the peak of W 4f appears at 31.20 eV.The peaks of Re 4f 7/2 and 4f 5/2 are located at 41.45 and 43.83 eV, respectively.This indicates the successful doping of Re and W atoms.It is the doping of both types of atoms that leads to the shift observed in the XPS peaks of Mo and S. The existing studies reveal that Redoped MoS 2 shows red-shifted Mo 3d characteristic peaks and blue-shifted S 2p characteristic peaks, indicating the formation of n-type doping as the Fermi energy level moves away from the valence band.On the other hand, when W is doped into MoS 2 , the Mo 3d characteristic peaks also exhibit red-shifts, while the S 2p peaks show red-shifts as well.This suggests the formation of p-type doping, possibly due to the substitutional W ions possessing fewer valence electrons and more holes compared to Mo ions (work function: W:4.5 eV, Mo:4.37 eV).In our study, after the co-doping of Re and W, it is observed that red-shifted Mo 3d characteristic peaks and blue-shifted S 2p characteristic peaks, indicating that the Fermi energy level is considerably away from the valence band.Therefore, it can be inferred that the content of Re is higher than the content of W. Based on the analysis of the measured composition, the new material's composition was determined as Re 0.15 W 0.05 Mo 0.80 S 2 .
shows the atomically resolved HR-STEM image with Z-contrast (Z Re = 75, Z W = 74, Z Mo = 42, and Z S = 16) for the doped sample, which shows a clear hexagonal lattice structure for the sample.Due to

Figure 4 .
Figure 4. a) Formation energy of W doping MoS 2 and Re doping in MoS 2 under S-poor and S-rich conditions.b) Density of states (DOS) calculations for the intrinsic W-Re co-doped MoS 2 .c,d) Band structures of the intrinsic MoS 2 and Re 0.15 W 0.05 Mo 0.80 S 2 .

Figure 5 .
Figure 5. a) Schematic diagram of the Re 0.15 W 0.05 Mo 0.80 S 2 photodetector.b) Current versus incident powers curve of Re 0.15 W 0.05 Mo 0.80 S 2 photodetector illuminated by 365 nm wavelength light.Device performance changes of Re 0.15 W 0.05 Mo 0.80 S 2 photodetector, which were measured at a wavelength of 365 nm.c,d) The occurrence of photocurrent in repeated dark and light environments.c) Photocurrent versus time curve of Re 0.15 W 0.05 Mo 0.80 S 2 photodetector illumination.The corresponding rise time and fall time are shown in panel (d).The performance of the Re 0.15 W 0.05 Mo 0.80 S 2 photodetector varies with the change of the incident power including e) photocurrent and responsivity, and f) noise equivalent power and normalized detectivity.