Kinetics of Ga and In desorption from (7 × 7) Si(1 1 1) and (3 × 3) 6H-SiC(0 0 0 1) surfaces

The desorption characteristics of Ga and In on (7 × 7) Si(1 1 1) and (3 × 3) 6H-SiC(0 0 0 1) surfaces have been determined using temperature programmed desorption. Two peaks were observed for desorption of a 1.5 ± 0.25 monolayer of Ga from the latter surface. The peak at T_max = 670 °C exhibited zeroth order kinetics; the activation energy and pre-exponential were determined to be 2.6 ± 0.1 eV and 6 × 10^{27 ± 0.5} atom/cm² s, respectively. The peak at T_max = 535 °C exhibited first order desorption kinetics with an activation energy and pre-exponential of 6.2 ± 0.3 eV and 7 × 10^{21 ± 2} s^-1, respectively. In contrast, only zeroth order kinetics and a lower activation energy of 2.0 ± 0.1 eV were determined for desorption of a 1.5 ± 0.25 monolayer of Ga from (7 × 7) Si(1 1 1). The values of these results in tandem with those of related studies of desorption from Si and SiC surfaces indicate that the low and high temperature Ga peaks from SiC are due to desorption from either a wetting layer or adatom sites and from Ga islands, respectively. The difference in desorption activation energies for Ga on Si(1 1 1) and on 6H-SiC(0 0 0 1) surfaces is attributed to differences in lattice matching of Ga to these surfaces. By contrast, only multilayer desorption was observed for 4 ± 1 monolayer of In on SiC(0 0 0 1). The zeroth order desorption activation energy and pre-exponential were 2.4 ± 0.1 eV and 6 × 10^27±0.5 atom/cm² s; they are consistent with the heat of sublimation (2.45-2.5 eV) for liquid In.