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A Model for Surface Space Charge Mediated Ultraviolet Photoresponse in MgZnO Thin Films and Its Experimental Verification
摘要： We propose a model based on the evolution of electron and surface charge density to describe the ultraviolet photoresponse in MgZnO thin films. The MgZnO surface contains a high density of surface bound states for electrons due to chemisorption of oxygen molecules, resulting in formation of a surface depletion region. We take into account the change in both conducting volume and electron density in the nondepleted part of the MgZnO thin films upon UV illumination to model temporal variation of photocurrent. We have deposited a set of MgZnO thin films on Al electrodes by pulsed laser deposition at different oxygen pressures to verify the model. With increasing oxygen pressure, dark current, peak responsivity, and response time decreased while the ON?OFF ratio and UV to visible rejection ratio increased, implying different levels of oxygen chemisorption. The proposed model has been successfully used to simulate the temporal decay of the photocurrent in the deposited devices.
关键词： model for photocurrent decay,ultraviolet photoresponse,MgZnO thin films,oxygen chemisorption,surface space charge
更新于2025-09-23 15:19:57
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Growth of BaSi <sub/>2</sub> film on Ge(100) by vacuum evaporation and its photoresponse properties
摘要： We have successfully grown a polycrystalline orthorhombic BaSi2 film on a Ge(100) substrate by an evaporation method. Deposition of an amorphous Si (a-Si) film on the Ge substrate prior to BaSi2 evaporation plays a critical role in obtaining a high-quality BaSi2 film. By controlling substrate temperature and the thickness of the a-Si film, a crack-free and single-phase polycrystalline orthorhombic BaSi2 film with a long carrier lifetime of 1.5 μs was obtained on Ge substrates. The photoresponse property of the ITO/BaSi2/Ge/Al structure was clearly observed, and photoresponsivity was found to increase with increasing substrate temperature during deposition of a-Si. Furthermore, the BaSi2 film grown on Ge showed a higher photoresponsivity than that grown on Si, indicating the potential application of evaporated BaSi2 on Ge to thin-film solar cells.
关键词： photoresponse properties,Ge substrate,thin-film solar cells,BaSi2,vacuum evaporation
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Shenzhen, China (2019.9.3-2019.9.6)] 2019 IEEE 4th Optoelectronics Global Conference (OGC) - Ultra-sensitive Detection of Heavy Metal Using a Fiber Grating-Assisted Plasmonic Electrochemical Sensor
摘要： We demonstrate the performance enhancement of field-effect transistor (FET)-based plasmonic terahertz (THz) detector with monolithic integrated antenna in low-impedance regime and report the experimental results of Si MOSFET impedance in THz regime using 0.2-THz measurement system. By designing FET with low-impedance ranges (<1 kΩ) and integrating antennas with impedances of 50 and 100 Ω, we found that our low-impedance MOSFETs have the input impedance criterion of 50 Ω at 0.2 THz and the MOSFETs with thinner gate oxide show the highly enhanced plasmonic photoresponses at 50-Ω antenna by 325 times from the result of the detector without antenna.
关键词： terahertz,impedance,photoresponse,MOSFET,detector,plasmonic
更新于2025-09-23 15:19:57
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Growth dynamics and photoresponse of the Wadsley phase V <sub/>6</sub> O <sub/>13</sub> crystals
摘要： The preparation of a pure phase has long been the key obstacle for the fundamental research and device application of Wadsley vanadium oxides (VnO2n+1) due to the mixed-valence feature and closeness in thermodynamic phase diagrams. Herein, we demonstrate a melt-assisted pyrolysis process to prepare pure V6O13 (n = 6) using a V2O5 precursor film. V6O13 with an atomic flat (00l) terrace and length up to a millimeter was prepared on a c-cut sapphire surface. Both ex situ and in situ real-time investigations on the growth process reveal that the melting and decomposition of V2O5 started as synchronization processes for the nucleation of V6O13. The endothermic melting process provides the main driving force for the rapid growth of V6O13 crystals along the melt/solid interface. The as-prepared V6O13 crystal sheets show a broadband photoresponse capability (0.4–8.8 mm) with a rise/fall time of 42 ms/50 ms, and the maximum EQE of 5.4 (cid:2) 104%. Spatial photocurrent imaging reveals that both photoelectric and bolometer effects contribute to the photoresponse. This study offers a feasible and scalable method for the preparation of high quality mix-valence vanadium oxide for future opto-electrical and energy storage devices.
关键词： Wadsley phase,V6O13,photoresponse,melt-assisted pyrolysis,vanadium oxides
更新于2025-09-23 15:19:57
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Defect mediated transport in self-powered, broadband and ultrafast photoresponse of MoS <sub/>2</sub> /AlN/Si based photodetector
摘要： By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here we report a self-powered and ultrafast photodetector based on hybrid MoS2/AlN/Si heterostructure. The heterojunction is formed by depositing MoS2 thin film by pulsed laser deposition on AlN/Si(111) template. The vertical transport properties of the device under dark and light illumination conditions, exhibit an excellent photoresponse in a broad range of wavelengths (300–1100 nm) at 0 V. The maximum responsivity of this photodetector is found to be 9.93 A/W at wavelength of 900 nm. The device shows an ultrafast temporal response with response/recovery times of 12.5/14.9 μs. X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy reveal presence of native oxygen impurities in AlN, throughout the bulk of the film. These oxygen defects form a deep donor level in AlN and play a crucial role in the transport of the photogenerated carriers, resulting in enhanced device performance.
关键词： broadband and ultrafast photoresponse,deep defects,MoS2,AlN,pulsed laser deposition
更新于2025-09-23 15:19:57
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High-speed femtosecond laser plasmonic lithography and reduction of graphene oxide for anisotropic photoresponse
摘要： Micro/nanoprocessing of graphene surfaces has attracted significant interest for both science and applications due to its effective modulation of material properties, which, however, is usually restricted by the disadvantages of the current fabrication methods. Here, by exploiting cylindrical focusing of a femtosecond laser on graphene oxide (GO) films, we successfully produce uniform subwavelength grating structures at high speed along with a simultaneous in situ photoreduction process. Strikingly, the well-defined structures feature orientations parallel to the laser polarization and significant robustness against distinct perturbations. The proposed model and simulations reveal that the structure formation is based on the transverse electric (TE) surface plasmons triggered by the gradient reduction of the GO film from its surface to the interior, which eventually results in interference intensity fringes and spatially periodic interactions. Further experiments prove that such a regular structured surface can cause enhanced optical absorption (>20%) and an anisotropic photoresponse (~0.46 ratio) for the reduced GO film. Our work not only provides new insights into understanding the laser-GO interaction but also lays a solid foundation for practical usage of femtosecond laser plasmonic lithography, with the prospect of expansion to other two-dimensional materials for novel device applications.
关键词： graphene oxide,photoreduction,anisotropic photoresponse,femtosecond laser,plasmonic lithography
更新于2025-09-23 15:19:57
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A Mixed-Dimensional van der Waals Heterostructure Photodetector
摘要： Van der Waals (vdW) heterostructures, integrated two-dimensional (2D) materials with variously functional materials, provide a distinctive platform for next-generation optoelectronics with unique flexibility and high performance. However, exploring the vdW heterostructures combined with strongly correlated electronic materials is hitherto rare. Herein, a novel temperature-sensitive photodetector based on the GaSe/VO2 mixed-dimensional vdW heterostructure is discovered. Compared with previous devices, our photodetector exhibits excellently enhanced performance, with external quantum efficiency up to 109.6 % and the highest responsivity (358.1 mA?W?1) under a 405 nm laser. Interestingly, we show that the heterostructure overcomes the limitation of a single material under the interaction between VO2 with GaSe, where photoresponse is highly sensitive to temperature and can be further shut at the critical value. The metal-insulator transition of VO2, which controls the peculiar band-structure evolution across the heterointerface, is demonstrated to manipulate the photoresponse variation. This study enables us to elucidate the method of manipulating 2D materials by strongly correlated electronic materials, paving the way for developing the high-performance and special optoelectronic application.
关键词： gallinum selenide,Vanadium dioxide,MIT-controlled photoresponse,mixed-dimensional van der Waals heterostructure,band engineering
更新于2025-09-23 15:19:57
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Novel Self-Powered Photodetector with Binary Photoswitching Based on SnS <sub/><i>x</i> </sub> /TiO <sub/>2</sub> Heterojunctions
摘要： Binary photoresponse characteristics can realize the optical signal processing and logic operations. The UV photodetectors (PDs) with SnSx nanoflakes and TiO2 nanorod arrays (NRs) show a novel binary photoswitching behavior (change in current from positive to negative) by manipulating the light wavelength without external power source, utilizing the interfacial recombination of the photogenerated carriers in the type-I SnSx/TiO2 heterojunctions. The enhanced responsivity (R*) and detectivity and fast photoresponse time for self-powered SnSx/TiO2 PDs can be achieved by adjusting the phase ratio of SnS and SnS2 nanoflakes. The binary photoswitching in the self-powered UV PDs can be applied in the encrypted optical signal processing and imaging in some special conditions without external bias.
关键词： self-powered photodetector,SnSx/TiO2,binary photoresponse,heterojunctions
更新于2025-09-23 15:19:57
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Growth of Si2Te3/Si heterostructured nanowire and its photoresponse property
摘要： Single-crystalline heterostructured Si2Te3/Si nanowires (H-NWs) were synthesized by using gold nanoclusters as a catalyst. Control of the nanowire structures could be achieved by substrate temperature and growth time. Scanning electron microscopy (SEM) study shows that the as-grown nanowires are composed of two parts: one part has a conical shape with gold catalyst on the top and second part is uniform nanowire. High-resolution transmission microscopy study shows that the H-NWs have a core/shell structure with a silicon nanowire core wrapped by a Si2Te3 shell. The composition of the core-shell structure was confirmed by Energy-dispersive X-ray spectrometry (EDX) measurements. X-ray diffraction (XRD) and Raman spectra confirm the two types of crystal structure of silicon and Si2Te3 in H-NWs. A possible growth mechanism of H-NWs is discussed. The photoresponse property of Si2Te3/Si H-NW is observed under illumination of light. The rise and decay time constants are ~590 ms and ~800 ms, respectively. The unique structure and properties of these silicon-based nanowires of 2D materials are not only interesting for fundamental understanding but also potential building blocks for applications in optoelectronic devices.
关键词： Nanowire,Si2Te3,Core-Shell,Si,Heterostructure,Photoresponse
更新于2025-09-19 17:13:59
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Incorporating Aluminum Plasmonic Nanohemisphere Arrays into Organic Ultraviolet Photodetectors for Improved Photoresponse
摘要： Aluminum nanostructures, which support surface plasmon resonances in the UV spectral range, were incorporated into conventional organic UV photodetectors with a structure of indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly(9,9-dioctyl?uorene-alt-bithiophene) (F8T2):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM)/LiF/Al. Nanohemisphere arrays (NHSAs) were imprinted into the top surface of the soft organic active layer, thus transferring the pattern to the subsequently thermally deposited layers of LiF and Al. NHSA-top devices and ?at-top control devices were investigated by 3-dimensional ?nite-di?erence time-domain (3D-FDTD) electromagnetic simulations. Improved UV active layer absorbance and enhanced electric ?elds in the nanohemispheric region at the top of the active layer were shown for devices with the NHSA-top. The impact of the NHSA-top was found to be more signi?cant for devices with thin active layers and to gradually decrease with increasing active layer thickness. Fabricated NHSA-top devices with thin active layers exhibited improved photoresponse in terms of external quantum e?ciency, speci?c detectivity and on?o? response speed compared to ?at-top devices under 330 nm illumination and 0 to ?1 V bias. The method developed in this work provides a versatile and e?ective way to incorporate plasmonic nanostructures into optoelectronic devices to enhance device performance.
关键词： enhanced photoresponse,aluminum plasmonic nanostructures,organic photodetectors,nanoimprinting,ultraviolet photodetectors
更新于2025-09-19 17:13:59