Interaction of hydrogen with chemical vapor deposition diamond surfaces: A thermal desorption study

Abstract

The interaction of hydrogen with a chemical vapor deposition (CVD) deposited polycrystalline film on Si(100), cleaned by heating to 1500 K, has been examined. No adsorption is observed unless prior activation with a hot filament is carried out. However atomic H thereby created is found to adsorb with a high sticking probability, subsequently desorbing in the temperature range 1100–1225 K. Etching of the diamond surface, producing gaseous methane and ethane is also seen. The reactivity patterns are rather similar to those observed on C(100) and C(111) surfaces, suggesting these are suitable model substrates for the study of reaction mechanisms associated with CVD diamond growth. However, a major difference is also seen in that a mixture of hydrogen, silane, and disilane, with other minority species, is seen to evolve from the surface of the CVD diamond film at 1275 K when exposed to the reacting gas and is not detected from single-crystal diamond surfaces. The results indicate that this arises from the selective etching of Si present at grain boundaries in the deposited films.