SIMULTANEOUS CHARACTERIZATION OF DEFECT STATES IN CVD DIAMOND BY PDS,EPR, RAMAN AND PHOTOCURRENT SPECTROSCOPIES

The assessment of the quality of CVD diamond films, a very important i ssue for the preparation of electronics-quality material, has been app roached with the help of Raman, luminescence and photocurrent spectros copy, photothermal deflection spectroscopy (PDS) and electron paramagn etic resonance (EPR). In heteroepitaxial diamond films deposited on si licon wafers by plasma-enhanced chemical vapour deposition (PECVD) we have observed the following defects: sp(2) bonded carbon, carbon dangl ing bonds, nitrogen and silicon. Raman scattering is sensitive to sp(2 ) bonded carbon, PDS sees total absorption due to sp(2) bonded carbon, dangling bonds and nitrogen. Typically, the graphitic inclusions betw een the grains dominate the PDS spectrum. EPR detects carbon dangling bonds (vacancy-like defect, with possible H involvement) with g = 2.00 28 and paramagnetic form of nitrogen with g = 2.0024. A strong photolu minescence peak at 1.68 eV reflects the Si contamination, Nitrogen-rel ated transitions were detected by photocurrent measurement, with a cha racteristic threshold at about 2.1 eV, and seen in luminescence. A thr eshold energy of approximately 1 eV was attributed to the carbon dangl ing bond defect, which was observed also by EPR. This g = 2.0028 signa l decreases with an increase in material quality, as determined by Ram an spectra. (C) 1998 Elsevier Science S.A.