High-performance p–n heterojunction photodetectors based on V2O5 nanorods by spray pyrolysis

Light-Sensing Properties of Amorphous Vanadium Oxide Films Prepared by RF Sputtering

In this study we analyzed the structure and light-sensing properties of as-deposited vanadium oxide thin films, prepared by RF sputtering in different Ar:O₂ flow rate conditions, at low temperature (e.g., 65 °C). X-ray diffraction (XRD), Scanning Electron Microscopy (SEM-EDX), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to analyze the film microstructure, composition and the oxidation states of vanadium ions. The SEM micrographs evidence V_xO_y films with smooth surfaces, whereas the XRD patterns show their amorphous structure. Raman spectra indicate an increased structural disorder in the films deposited in Ar:O₂ flow comparatively with those deposited solely in Ar flow. The XPS data suggest the modification of the oxidation state from V⁴⁺ to V⁵⁺, thus proving the formation of the V₂O₅ phase when increasing the oxygen content, which further affects the films' optical properties. We observed a good stability of the photogenerated current in Si/SiO₂/V_xO_y/TiN heterostructures upon excitation with pulses of UV (360 nm), VIS (white light) and NIR (860 nm) light. The responsivity, detectivity and linear dynamic range parameters increase with the O/V ratio in the V_xO_y films, reaching comparable values with photodetectors based on crystalline V₂O₅ or VO₂.

Facile Synthesis of Two Dimensional (2D) V2O5 Nanosheets Film towards Photodetectors

Most of the studies focused on V₂O₅ have been devoted to obtaining specific morphology and microstructure for its intended applications. Two dimensional (2D) V₂O₅ has the most valuable structure because of its unique planar configuration that can offer more active sites. In this study, a bottom-up and low-cost method that is hydrothermal combined with spin-coating and subsequent annealing was developed to prepare 2D V₂O₅ nanosheets film on quartz substrate. First, VOOH nanosheets were prepared by the hydrothermal method using V₂O₅ powders and EG as raw materials. Further, V₂O₅ nanosheets with an average lateral size over 500 nm and thickness less than 10 nm can be prepared from the parent VOOH nanosheets by annealing at 350 °C for 15 min in air. The prepared V₂O₅ nanosheets film was assembled of multiple nanosheets. The structural, morphological, microstructural and optical properties of the films were respective investigated by XRD, SEM, TEM and UV-Vis. The photodetector based on V₂O₅ nanosheets film shows good photoresponse with a response time of 2.4 s and a recovery time of 4.7 s.

Construction of Schottky contact by modification with Pt particles to enhance the performance of ultra-long V2O5 nanobelt photodetectors

Schottky-contacted nanosensors have attracted extensive attention due to their high sensitivity and fast response time. In this article, we proved that the construction of Schottky contact by Pt nanoparticles (NPs) decoration can effectively improve the performance of V₂O₅ nanobelts photodetectors. After modified by Pt NPs, the photocurrent of V₂O₅ nanobelts is increased by more than two orders of magnitude, and the photoresponse speed is improved by at least three orders of magnitude. Detailed studies have shown that the performance enhancement is attributed to the formation of the Schottky contact at the electrode-semiconductor interface due to the decrease of surface gas adsorption and the increase of V₂O₅ work function after Pt NPs modification. The strong built-in field in the Schottky barrier region will quickly separate photogenerated carriers, thereby reducing the electron-hole recombination rate, resulting in the fast response time and an increase in the free carrier density. Moreover, it is found that this enhancement effect can be regulated by controlling the pressure to modulating the Schottky barrier height at the interface. Overall, the Pt NPs-modified V₂O₅ nanobelts photodetector exhibits a broad response spectrum (visible to near infrared), fast rise/fall response time (less than 6.12/6.15 ms), high responsivity (5.6 A/W), and high specific detectivity (6.9 × 10⁸ Jones). This study demonstrates the feasibility of building a Schottky barrier to enhance the photodetection performance, which provides a general and effective strategy towards the construction and its practical application of supersensitive and fast-response nanosensors.