Diamond epitaxial films with a thickness of 200-350 Å were grown on C(001) surfaces by gas source molecular beam epitaxy (GSMBE) with pure methane (CH4) and without the addition of hydrogen or oxygen. From Arrhenius plots of the growth rates, the activation energy (Ea) of the growth was found to be 15 kcal/mol. To clarify the rate-limiting reaction of the diamond epitaxial growth in this GSMBE, the reaction coefficients of CH4 adsorption and H2 desorption were obtained by measuring the time evolution curves of the surface hydrogen coverage (θH) by electron stimulated desorption of H+ ions. From Arrhenius plots of the reaction coefficients, the Ea's of CH4 adsorption and H2 desorption on C(001) surface were estimated to be 7.3 ± 1.7 and 21 ± 4.9 kcal/mol, respectively. Ea for H2 desorption is close to Ea for diamond growth, which suggests that the rate of GSMBE diamond growth is limited by hydrogen desorption. This is further supported by the experimental observation that the growth rate is largely independent of the CH4 pressure. It was also found that θH does not disappear completely but has a large saturation value of ∼30-60% of initial θH, depending on the desorption temperature, which will be discussed in terms of surface segregation of hydrogen from the bulk.
|ジャーナル||New Diamond and Frontier Carbon Technology|
|出版ステータス||Published - 1996 12 1|
ASJC Scopus subject areas
- Materials Science(all)
- Surfaces and Interfaces
- Surfaces, Coatings and Films