Photocurrent and photoelectron yield spectroscopies of defect states in CVD diamond films

Photocurrent (PC) and photoelectron yield (PY) measurements have been used to investigate defect states in CVD diamond. Diamond films exhibit a non-negligible sub-band-gap photocurrent with a well defined energy onset related to the photoionization of acceptor-like defects located in the range 1.2-1.3 eV. The PC energy onset is shifted to lower energy by chemical treatment in sulphochromic acid, which leads to the appearance of a photoionization band in the photocurrent spectrum. On the other hand, PY spectra closely follow a power law with an energy threshold in the range of 4.3-4.4 eV, which also shift to higher energies after the same chemical treatment. The resulting defect level scheme consistent with both PC and PY results is discussed