The  in situ  doping of chemical vapor deposited material, with N and Li, was carried out by using organometallic precursors. Photo-thermal deflection spectroscopy was used to monitor optical transitions from localized electronic states, in the band-gap, which resulted from the presence of extrinsic and intrinsic impurities. The optical absorption of N-doped films (100ppm in the gas phase) revealed absorption bands which were characteristic of Ib diamond. When a Li-containing precursor was used, a deep defect (at around 1.5eV) was observed which had not previously been reported. Optical transitions due to this defect state were superposed on the characteristic background absorption.

M.Nesladek, K.Meykens, L.M.Stals, C.Quäyhägens, M.D’Oliesläger, T.D.Wu, M.Vanecek, J.Rosa: Diamond and Related Materials, 1996, 5[9], 1006-11