EFFECT OF THE CHEMICAL NATURE OF TRANSITION-METAL SUBSTRATES ON CHEMICAL-VAPOR-DEPOSITION OF DIAMOND

Chemical-vapor deposition of diamond on transition-metal substrates of Cu, Ni, Fe, and their alloys NiAl, Ni3Al, FeSi2, and FeSi has been investigated. It is shown that diamond grows easily on Cu with a very small amount of graphite, while on Ni and Fe there is rapid growth of the graphite layer before diamond deposition. The formation of graphite is attributed to the decomposition of carbon-containing precursors due to the strong catalytic reactivity of Ni and Fe substrates with carbon. The deactivation of these substrates by forming NiAl and FeSi2 results in the suppression of graphite and formation of high-quality diamond. However, for Ni3Al and FeSi substrates which are not completely deactivated, deposition of graphite still takes place. A mechanism based on the electronic structure of substrate atoms, particularly on the 3d shell structure of Cu, Ni, and Fe is proposed to understand the above behavior. Requirements for the stabilization of sp3 bonding of carbon on different substrates are discussed.