Abstract:A plasma-enhanced chemical vapor deposition system was used to fabricate ultraviolet (UV) photodetectors based on polar and nonpolar zinc oxide (ZnO) thin films combined with interdigitated platinum top electrodes. The performance of photodetectors was demonstrated by current–voltage characteristics and time-dependent photoresponse measurements. Both polar and nonpolar detectors showed a prominent photocurrent gain under UV light illumination, compared with dark conditions. However, the response and recovery t… Show more
“…Moreover, carrier recombination and tunneling across the device junction may be addressed as a reason for the enhancement I–V under UV illumination. Nevertheless, fast response and recovery times, high responsivity, high reliability, and low signal-to-noise ratio are important characteristics for detector applications 77 , 78 , which is discussed below in detail. Figure 10 The semi-logarithmic scale I–V of MoWO 3 /VO 2 /MoS 2 /Si device under dark and UV illumination with MoS 2 sputtering time of ( a ) 30, ( b ) 60, ( c ) 120, ( d ) 180, and ( e ) 240 s. …”
Section: Resultsmentioning
confidence: 99%
“…The induced photocurrent I ph is given by , where increases with increasing the applied voltage and the light power 82 . Photocurrent gain (P g ) can be defined and determined by , where and are photocurrent and dark current respectively 77 .…”
The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.
“…Moreover, carrier recombination and tunneling across the device junction may be addressed as a reason for the enhancement I–V under UV illumination. Nevertheless, fast response and recovery times, high responsivity, high reliability, and low signal-to-noise ratio are important characteristics for detector applications 77 , 78 , which is discussed below in detail. Figure 10 The semi-logarithmic scale I–V of MoWO 3 /VO 2 /MoS 2 /Si device under dark and UV illumination with MoS 2 sputtering time of ( a ) 30, ( b ) 60, ( c ) 120, ( d ) 180, and ( e ) 240 s. …”
Section: Resultsmentioning
confidence: 99%
“…The induced photocurrent I ph is given by , where increases with increasing the applied voltage and the light power 82 . Photocurrent gain (P g ) can be defined and determined by , where and are photocurrent and dark current respectively 77 .…”
The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.
“…The definition of response time was based on the time duration for reaching 90% of the full response of the detector. Several work including ours were performed on studies of response and recovery times of photodetectors but the focus of the most work is on ZnO or boron nitride based photo detectors 6 31 32 . For the present SiC case, the response times at the first several cycles are long and become shorter as more cycles are completed.…”
We report on a new approach to quickly synthesize high-quality single crystalline wide band gap silicon carbide (SiC) films for development of high-performance deep ultraviolet (UV) photodetectors. The fabricated SiC based UV photodetectors exhibited high response while maintaining cost-effectiveness and size miniaturization. Focus of the experiments was on studies of electrical and electronic properties, as well as responsivity, response and recovery times, and repeatability of the deep UV photodetectors. Raman scattering spectroscopy and scanning electron microscope (SEM) were used to characterize the SiC materials. Analyses of the SEM data indicated that highly flat SiC thin films have been obtained. Based on the synthesized SiC, deep UV detectors are designed, fabricated, and tested with various UV wavelength lights at different radiation intensities. Temperature effect and bias effect on the photocurrent strength and signal-to-noise ratio, humidity effect on the response time and recovery time of the fabricated detectors have been carefully characterized and discussed. The detectors appear to have a very stable baseline and repeatability. The obtained responsivity is more than 40% higher compared to commercial detectors. The good performance of the photodetectors at operating temperature up to 300 °C remains nearly unchanged.
“…Until now, many research works have been reported about the hydrophobic/hydrophilic reversible process caused by light-controlled method for ZnO-based nanostructures 17 18 19 20 . ZnO has direct wide band gap (3.37 eV), high exciton binding energy (60 meV) and optical transparency in the visible light, thus, ZnO is an expected material for many novel applications, for example, piezoelectric transducers, transparent thin film transistors, chemical biosensors 21 22 , solar cells and ultraviolet (UV) detectors 23 24 25 . According to the above functionalities, ZnO can provide a hydrophobic surface, which may be transformed to hydrophilic surface by UV irradiation, coexists with intrinsic semiconductor properties and a particular surface morphology.…”
The energetic particles bombardment can produce large internal stress in the zinc oxide (ZnO) thin film, and it can be used to intentionally modify the surface characteristics of ZnO films. In this article, we observed that the internal stress increased from −1.62 GPa to −0.33 GPa, and the naturally wettability of the textured ZnO nanostructured films changed from hydrophobicity to hydrophilicity. According to analysis of surface chemical states, the naturally controllable wetting behavior can be attributed to hydrocarbon adsorbates on the nanostructured film surface, which is caused by tunable internal stress. On the other hand, the interfacial water molecules near the surface of ZnO nanostructured films have been identified as hydrophobic hydrogen structure by Fourier transform infrared/attenuated total reflection. Moreover, a remarkable near-band-edge emission peak shifting also can be observed in PL spectra due to the transition of internal stress state. Furthermore, our present ZnO nanostructured films also exhibited excellent transparency over 80% with a wise surface wetting switched from hydrophobic to hydrophilic states after exposing in ultraviolet (UV) surroundings. Our work demonstrated that the internal stress of the thin film not only induced natural wettability transition of ZnO nanostructured films, but also in turn affected the surface properties such as surface chemisorption.
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