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 issue for the preparation of electronics-quality material, has been approached with the help of Raman, luminescence and photocurrent spectroscopy, photothermal deflection spectroscopy (PDS) and electron paramagnetic resonance (EPR). In heteroepitaxial diamond films deposited on silicon wafers by plasma-enhanced chemical vapour deposition (PECVD) we have observed the following defects: sp2 bonded carbon, carbon dangling bonds, nitrogen and silicon. Raman scattering is sensitive to sp2 bonded carbon, PDS sees total absorption due to sp2 bonded carbon, dangling bonds and nitrogen. Typically, the graphitic inclusions between the grains dominate the PDS spectrum. EPR detects carbon dangling bonds (vacancy-like defect, with possible H involvement) with g=2.0028 and paramagnetic form of nitrogen with g=2.0024. A strong photoluminescence peak at 1.68 eV reflects the Si contamination. Nitrogen-related transitions were detected by photocurrent measurement, with a characteristic threshold at about 2.1 eV, and seen in luminescence. A threshold energy of approximately 1 eV was attributed to the carbon dangling bond defect, which was observed also by EPR. This g=2.0028 signal decreases with an increase in material quality, as determined by Raman spectra.