Some Surface Properties of Silicon-Carbide Crystals

The work functions of a number of commercial-grade silicon-carbide single crystals have been obtained in high vacuum (p<10−9 mm Hg). Low-energy electron-diffraction studies have also been made for one of these samples. Surfaces cleaned by argon-ion bombardment and annealing appeared to contain an excess of carbon. Heating for long periods of time at 1000°C also appeared to produce surfaces which were nonstoichiometric. Oxygen was adsorbed at room temperature on the ion-bombardment cleaned surfaces with a sticking coefficient of the order of 0.01. Differences in adsorption properties were noted which were probably associated with asymmetry in atomic species on different crystal faces. Work-function values on opposite faces of any crystal were the same. Hydrogen exposure resulted in work-function decreases only in the presence of a heated filament. Under similar conditions of ion bombardment and high-temperature heating, the SiC surfaces appeared to be more stable than those of silicon crystals.