High resolution Auger electron spectroscopy studies on (100) and (111) facets of chemical vapor deposited diamond

Abstract

Diamond thin films were grown by microwave plasma and hot filament chemical vapor deposition (MPCVD and HFCVD, respectively) techniques. Films were systematically characterized by x-ray diffraction, micro-Raman spectroscopy, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES). Although the results obtained using various characterization techniques are broadly similar, there are however subtle differences. For instance, Raman spectra show a sharp peak at ≃ 1332 cm−1 corresponding to natural diamond in both types of films. The intensity and the position of the non-diamond band in the two sets of films differ. While the maxima of the non-diamond band in HFCVD film lies at 1450 cm−1, in MPCVD film it occurs at 1525 cm−1. Also the values of FWHM in HFCVD film (≃ 7.5 cm−1) are smaller than the MPCVD films (≃ 9.5 cm−1). This may indicate that the concentration of non-diamond carbon impurities on the grain boundaries of HFCVD films are really small. SEM results on the other hand indicate that the grain size of the MPCVD films is larger than HFCVD films. AES was performed in a survey scan (beam size ∼10 μm × 8 μm) and high resolution (beam size ≃ 0.2 μm) mode with an initial aim to investigate the surface characteristics and environment of carbon atoms of the diamond films. In the survey scan, the spectra show a line shape typical of CVD diamond films. Anomalous results were obtained when the AES was performed on (100) and (111) facets in high resolution mode. This may be explained in terms of the surface reconstruction taking place due to hydrogen desorption via core-hole Auger decay process. Auger depth profiles were also obtained on the facets which reveal that Si, O, and N are the dominant impurities. The impurity content of HFCVD films is observed to be lower by a factor of 2 as compared to MPCVD films.