Femtosecond PLD-grown YF₃ nanoparticle thin films as improved filterless VUV photoconductive detectors

Abstract

A photoconductive detector (PCD) responding only to vacuum ultraviolet (VUV) radiations below 180 nm without any filter was fabricated using an yttrium fluoride (YF3) thin film grown by femtosecond (fs) laser pulsed laser deposition (PLD). The structural morphology (particle size and surface roughness) of the thin film was improved using a low laser fluence and a high substrate temperature during the fabrication. The smallest average particle size achieved was 159 nm with a roughness of 37 nm at a laser fluence of 13.5 J cm−2 and a substrate temperature of 400 °C. The resistances for the dark current of the PCD increased from 10 TΩ to 680 TΩ using YF3 thin films with a smaller average nanoparticle diameter of 159 nm rather than 330 nm. The time response of the PCD to a VUV flash lamp emitting at 170 nm showed that a small average nanoparticle diameter results to a fast response time. By covering the Al electrode pairs with another fs PLD-grown YF3 film, the influence of external photoelectric effect was suppressed and the response wavelength edge decreased from 280 nm to 180 nm without any filter. The filterless PCD is expected to enhance the use of fluoride thin films in conjunction with VUV light sources for various scientific and industrial applications.

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

“…Furthermore, we also investigate the improvement of its photoconductivity in the VUV region using TiO 2 thin films deposited on high resistivity undoped silicon (Si), quartz glass (SiO 2 ), and soda lime glass (SLG) substrates with thicknesses of 80 nm, 500 nm, and 1000 nm. Our results show that TiO 2 thin films in general—but especially TiO 2 thin films deposited on SiO 2 substrate with a thickness of 80 nm exhibit higher photoconductivity, with photocurrents reaching the milli-Ampere range, compared with our previous works using wide band gap fluorine-based insulator thin film photoconductive detectors [ 26 , 27 ] and gamma-ray irradiated detectors, based on amorphous TiO 2 on SLG substrate [ 28 ]. The potential of using TiO 2 thin films as photoconductive detectors of VUV radiation will contribute to the enhancement of the many applications of this high energy radiation.…”

Influence of Annealing on Thin Film/Substrate Interface and Vacuum Ultraviolet Photoconductivity of Neodymium Fluoride Thin Films

“…[32] We have previously demonstrated that fluoride crystals and thin films can be used as photoconductive detectors in the VUV region. [33][34][35][36][37] Their spectral response can be adjusted by controlling the respective composition ratios and optical quality. [33][34][35][36][37] Unlike silicon-based detectors developed by relatively mature production technologies and WBG semiconductor-based detectors, which are widely investigated in current literature, the development of fluoride photodetectors is in its infancy and thus not much is known regarding the correlation between fabrication parameters and photodetector performance.…”

“…[33][34][35][36][37] Their spectral response can be adjusted by controlling the respective composition ratios and optical quality. [33][34][35][36][37] Unlike silicon-based detectors developed by relatively mature production technologies and WBG semiconductor-based detectors, which are widely investigated in current literature, the development of fluoride photodetectors is in its infancy and thus not much is known regarding the correlation between fabrication parameters and photodetector performance. In this work, we investigated the influence of annealing on the interface between neodymium trifluoride (NdF 3 ) thin film and quartz (SiO 2 ) substrate.…”

Ultraviolet-C Photoresponsivity Using Fabricated TiO2 Thin Films and Transimpedance-Amplifier-Based Test Setup

“…The wavelength detection limit of such detectors is dictated by the band gap of the semiconductor material, without having to use optical filters. Furthermore, the band gap can be tuned by controlling the composition ratio [ 14 ] and the fabrication parameters [ 15 , 16 ]. Zinc oxide (ZnO) [ 17 ], gallium nitride (GaN) [ 18 ], aluminum nitride (AlN) [ 19 , 20 ], and boron nitride (BN) [ 21 , 22 , 23 , 24 , 25 ] are semiconductor materials that have been reported as UV photoconductive detectors, each with their own advantages and disadvantages.…”