Atomic-scale kinetic Monte Carlo simulations of diamond chemical vapor deposition.

摘要

Diamond's superb mechanical, thermal, optical, and electronic properties are ideally suited for use in protective coatings, thermal management components, cold cathode emitters, and high-performance electronic devices, among others. Diamond can be chemically vapor deposited (CVD) to produce coatings and thin films, but this technique is currently expensive and difficult to control, and the details of the molecular processes that lead to diamond deposition remain unclear. The goal of this work is to construct a tool by which the nano-scale processes that lead to diamond growth, and their effects on film properties, can be examined. This is accomplished through the development of a kinetic Monte Carlo simulation method that treats diamond deposition on the atomic length scale using established chemical reaction rate data as input, while addressing deposition time scales that correspond directly to real growth experiments. The impact of the atomic-scale surface reaction processes on the growth kinetics, surface morphologies, and defect densities of single crystal CVD diamond are examined. In this way, a clearer understanding of the connection between atomic-scale deposition processes and CVD diamond film properties can be obtained.; The growth kinetics and surface morphologies that develop during deposition are found to depend primarily on the details of the atomic surface features and their effects on bonding during deposition. The (110) and (111) surfaces facet under certain growth conditions. The (100) surface grows fastest and roughens, in contradiction to experimental observations. This can be rectified by the introduction of a mechanism for the preferential etching of monatomic islands on (100) facets, whereby the simulations predict slow-growing smooth (100) faces in accord with experimental observations.; The trapping of H atoms is enhanced at higher substrate temperatures where the flux of larger {dollar}rm Csb2Hsb2{dollar} molecules to the surface is high. Incorporation of sp{dollar}sp2{dollar} defects is highest for high-CH{dollar}sb4{dollar} feeds which generate less H, since H is required to convert sp2-bonded C on the surface to sp{dollar}sp3{dollar}-bonded material. Vacancy incorporation is not substantial. The ratio of simulated growth rate to defect concentration is maximized around 800-950{dollar}spcirc{dollar}C and 1% inlet CH{dollar}sb4,{dollar} for which experiments also produce the best quality CVD diamond.