Ga–CH3 bond scission by atomic H: The depletion of surface carbon from a gallium alkyl film on silicon dioxide

Abstract

It is shown that atomic hydrogen is an effective reagent for the extraction of CH3 groups from an adsorbed monolayer produced from trimethylgallium adsorption on SiO2. The reaction is first order in CH3 surface concentration and proceeds with zero activation energy in the 100 K temperature region. The efficiency for the extraction process is about 10−2 per atomic H collision with the surface. These results show that the Ga–CH3 bond may be broken by insertion of hydrogen atoms and that either CH3 or CH4 is eliminated by the process. The results indicate that atomic hydrogen is an effective agent for removal of carbon (present as CH3) during III–V film growth processes. The extraction of CH3 by atomic H occurs on the surface, but in metalorganic chemical vapor deposition processes a similar reaction with metal alkyl species may also occur in the gas phase. Excellent agreement with the theoretical calculations of Hiraoka and Mashita for the interaction of atomic H with AlH2(CH3) molecules is found.