A nondiamond phase at the interface between oriented diamond and Si(100) observed by confocal Raman spectroscopy

We have characterized bias-assisted chemical vapor deposition diamond using the nondestructive technique of confocal Raman spectroscopy to investigate the interfacial structures and the variation in structure and quality with depth. The spectral depth profiles of oriented diamond showed that a band centered at 1210 cm−1 and the diamond peak at 1332 cm−1 coexisted at the interface between the oriented diamond and Si substrate. The relative intensity of the 1210 cm−1 band compared to that of the diamond peak varied with depth. The intensity of the band decreased and that of the diamond peak increased from the interface to the diamond surface. The quality of the oriented diamond improved with the growth time. In contrast, for the case of a randomly oriented diamond, a band centered at 1550 cm−1 was observed, the diamond peak was shifted between −6 and 6 cm−1 from the single crystal diamond peak at 1332.5 cm−1, and the spectral profile did not change with depth. No band at 1210 cm−1 was seen in this case. We conclude that a nondiamond phase with a Raman band at 1210 cm−1 and a diamond phase coexist at the interface between the oriented diamond and the Si substrate, and that this 1210 cm−1 phase is therefore a characteristic feature of the nature of the diamond-substrate bonding in oriented films.