ABSTRACTGrowth and etch rates for diamond homoepitaxy have been measured in situ using Fizeau interferometry. Experiments were conducted in a hot-filament reactor using hydrogen, methane, and oxygen feed gases at a reactor pressure of 25 torr. The substrate temperature dependence for growth on diamond(lOO) was studied for 0.5% and 1% CH4 and 0–0.44% O2. Apparent activation energies of 17 and 5 kcal/mol were determined for growth from 0.5% and 1% CH4 in hydrogen, over the ranges of 700 – 1000 °C and 800 – 1050 °C, respectively. When a minimal amount of Oxygen was added to the feedstock, the growth-rate behavior was similar for that with pure methane. With greater amounts of added oxygen, growth rates were higher than those without Oxygen at low temperatures, proceeded through a maximum, and then decreased until etching was observed at high temperatures. Similar behavior was observed for growth from 1% CH4 with and without oxygen. We also measured the temperature dependence for etching of homoepitaxial diamond films in hydrogen with 0–0.1% O2, and observed etch rates of 0.01 – 0.1 microns/hr in the range of 950 – 1150 °C. We propose that oxygen facilitates diamond growth at low temperatures by enhancing the removal of both sp2- and sp3-bonded “errors” and/or by increasing the efficiency of carbon incorporation by roughening the diamond surface, and that these etching processes become dominant at high temperatures.
Unusual Dependence of the Diamond Growth Rate on the Methane Concentration in the Hot Filament Chemical Vapor Deposition Process