Very high UV-visible selectivity in polycrystalline CVD diamond films

Polycrystalline CVD diamond is a very attractive material for the fabrication of UV detectors. However, good quality material is required to obtain a high UV photoresponse together with a low visible sensitivity. In this work, we present and correlate the results of Raman spectroscopy, spectral photoresponse and thermally stimulated current (TSC) achieved on polycrystalline CVD diamond films. All the layers show the typical Raman diamond line with very small FWHM values, a broad TSC peak in the 480-530 K range, and have a high UV-visible selectivity (defined here as the ratio of the photosensitivity at 200 and 657 rim). This selectivity is found to increase when the FWHM of the Raman line decreases. In the same time, the mobility-lifetime product increases, and we observe both a shift in the TSC peak from 530 to 480 K and a decrease in the integrated trapped charge. For the best sample, the FWHM of the Raman line is 1.88 cm(-1), and the values of the mobility-lifetime product and of the UV-visible selectivity are as high as 1.5 x 10(4) cm(2) V-1, and 2 x 10(7), respectively, while the trap density estimated from the TSC experiment is in the range of loll cm(-3). (C) 2003 Elsevier B.V. All rights reserved.