Synthesis of SnO₂ nanowires using thermal chemical vapor deposition with SnO powder and their application as self-powered ultraviolet photodetectors

We report on the performance of self-powered ultraviolet (UV) photodetectors composed of SnO₂ nanowire (NW) networks. SnO₂ NWs with a length of several hundred micrometers can be synthesized by thermal chemical vapor deposition (CVD) using SnO powder as the raw material, which has the advantages of a low process temperature and no requirement for a reducing agent. Based on the characterization results obtained through synchrotron X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM), we determined the growth behavior of SnO₂ NWs via a vapor-liquid-solid mechanism with Au nanoparticles. The NW growth switched from an initial in-plane growth to subsequent vertical growth, forming NW cotton. This was started at a process temperature of 600 ℃ and optimized at 800 ℃. Moreover, the XRD and TEM results indicate that the NWs mainly grew in the form of SnO₂, although the formation of SnO NWs was also possible. Metal−SnO₂ NW−metal type photodetectors were fabricated, and their photoresponsivity to UV light in the range from 200 to 400 nm was investigated. The device exhibited a photo-to-dark current ratio of ∼2.17 × 10⁶ at an applied bias of 10 V and 254 nm UV exposure. A maximum responsivity of about 1100 A/W was estimated at a wavelength of 270 nm, and the cutoff edge wavelength appeared around 350 nm. In particular, the self-powered photoresponse at nominal zero bias was ∼1.23 nA. The results of this study support the idea that SnO₂ NWs are promising candidates for self-powered deep-UV photodetectors and that thermal CVD using SnO powder is suitable for synthesizing SnO₂ NWs at temperatures as low as 700 °C.