Spectroscopic identification of the reaction intermediates in the thermal decomposition of trimethylindium at GaAs(100) surfaces

Abstract

Abstract High resolution electron energy loss spectroscopy (HREELS) has been used to study the adsorption and thermal decomposition of trimethylindium (TMIn) on Ga-terminated GaAs(100) surfaces. HREEL spectra recorded for adsorption at room temperature are dominated by strong CH 3 deformation and stretching modes and indicate that the surface species is based on methyl groups. The intensities of these bands decrease with increasing temperature consistent with a primary decomposition route involving the loss of CH 3 groups from the surface. A small upward shift in the frequency of the symmetric and asymmetric CH 3 deformation modes is also observed with increasing temperature and indicates that decomposition takes place via an exchange reaction in which CH 3 groups switch from In to Ga due to the stronger Ga-C bond. At temperatures greater than 350°C, the spectra are dominated by CH 2 rocking, deformation and stretching vibrations. The presence of a surface methylene species at elevated temperatures suggests a second, minority decomposition pathway which involves dehydrogenation of surface CH 3 groups to CH 2 .