Thermally stimulated conductivity and luminescence in polycrystalline diamond films

Thermally stimulated currents (TSC) and thermoluminescence (TL) have been s tudied in polycrystalline diamond films of different qualities in order to gain information about the deep levels present within the bandgap of this m aterial. The TL has been studied between 300 and 670 K after UV light illum ination, and the TSC between 300 and 600 K after various excitations (UV li ght, from a tungsten lamp, X-rays). TL and TSC peaks are observed at 470 an d 560 K, and depend on the quality of the diamond and on the illumination c onditions. At low temperature three TSC peaks appear at 245, 283 and 312 K after illumination with a tungsten lamp. A spectral analysis of the 470 K l uminescence and electron emission measurement shows that the defect associa ted with this signal is an acceptor, and the hole released is trapped on a level 2.6 eV deep. Complementary ESR measurements show that paramagnetic ni trogen centers are not involved in the peak observed at 560 K.