INVESTIGATION OF N-DOPING IN CVD DIAMOND USING GAP STATES SPECTROSCOPY

In-situ doping of CVD diamond with N and Li using N-2 and a Li-contain ing organometaliic precursor was investigated. Photothermal deflection spectroscopy (PDS) was used to study optical transitions from localiz ed electronic states in the bandgap of CVD diamond resulting from the presence of extrinsic and intrinsic impurities. The advantage of PDS i s its sensitivity, which allows very low defect levels to be investiga ted even in thin diamond films. The optical absorption coefficient alp ha of N-doped films (100 ppm N-2 in the gas phase) shows absorption ba nds characteristic of Ib diamond. When a Li-containing precursor is us ed, a deep defect state around 1.5 eV, which has not been reported pre viously, is observed. Optical transitions due to this defect state are superimposed on the characteristic background absorption present in a ll CVD diamond films.