Effect of Substrate and Thickness on the Photoconductivity of Nanoparticle Titanium Dioxide Thin Film Vacuum Ultraviolet Photoconductive Detector

Vacuum ultraviolet radiation (VUV, from 100 nm to 200 nm wavelength) is indispensable in many applications, but its detection is still challenging. We report the development of a VUV photoconductive detector, based on titanium dioxide (TiO2) nanoparticle thin films. The effect of crystallinity, optical quality, and crystallite size due to film thickness (80 nm, 500 nm, 1000 nm) and type of substrate (silicon Si, quartz SiO2, soda lime glass SLG) was investigated to explore ways of enhancing the photoconductivity of the detector. The TiO2 film deposited on SiO2 substrate with a film thickness of 80 nm exhibited the best photoconductivity, with a photocurrent of 5.35 milli-Amperes and a photosensitivity of 99.99% for a bias voltage of 70 V. The wavelength response of the detector can be adjusted by changing the thickness of the film as the cut-off shifts to a longer wavelength, as the film becomes thicker. The response time of the TiO2 detector is about 5.8 μs and is comparable to the 5.4 μs response time of a diamond UV sensor. The development of the TiO2 nanoparticle thin film detector is expected to contribute to the enhancement of the use of VUV radiation in an increasing number of important technological and scientific applications.

Growth and UV detector of serrated GaN nanowires by chemical vapor deposition

Serrated GaN nanowires were synthesized on sapphire substrate by chemical vapor deposition. Copper nanowires were synthesized by liquid-phase reduction method. The surface morphology of GaN and copper nanowires was observed by scanning electron microscopy. An UV detector based on GaN nanowires was prepared with copper nanowires as electrode. The results show that the device is a photoconductive detector. The detector has different response under different wavelength light illumination and has the maximum response under 365nm ultraviolet light. Photocurrent–time characteristics show the detector has good stability over time.