Diamond Homoepitaxy Kinetics: Growth, Etching, and the Role of Oxygen

Abstract

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.