An X-ray photoelectron spectroscopy study of the surface layers between diamond crystallites and silicon substrate deposited by microwave-plasma-assisted chemical vapour deposition

Diamond growth by plasma chemical vapour deposition (CVD) on silicon has been characterized by ex situ X-ray photoelectron spectroscopy (XPS) and the composition of the surface layers between the crystallites and the silicon elucidated. Growth has been undertaken in both a standard Astex reactor and the Heriot-Watt ultrahigh vacuum system. A variety of conditions have been used, with growth temperatures in the range 500-900°C, pressures of 10-50 Torr, CH₄:H₂ ratios of up to 0.5% and microwave powers of up to 700 W. In one experiment O₂ was added to the gas mixture after growth had started. Depending primarily on the growth temperature, silicon carbide, silicon oxycarbide and silicon dioxide have been detected in various combinations and with differing stoichiometries. XPS angular dependence measurements show distinct layers with the carbide-rich phase nearest the silicon substrate and the oxygen-rich phase closest to the surface. On the basis of the ordering of the phases at the interface, a mechanism for the formation of the carbides is proposed. © 1993.