Surface properties and work function changes induced by atomic oxygen adsorbed on HfC(111) surface

Hafnium carbide (HfC) is regarded as one of the most promising cathode materials for field emission. But the experimental results did not provide a detail picture of the surface properties. In this work, we perform an ab initio study of the surface energies and work functions for the (1 0 0), (1 1 0), (1 1 1), (2 1 0), (3 1 0) and (3 1 1) surfaces of hafnium carbide. For the polar surface of (1 1 1) and (3 1 1) plane, a new method is taken to calculate the surface energy of the different surface terminations. The results indicate that the Hf termination surface is most stable, which are consistent with the experimental results. Additionally, we focused in particular on oxygen atom induced work function changes on HfC (1 1 1) plane as a function of coverage. An unexpected decrease of the work function is found at low coverage, and a reasonable resolution for this anomaly is given based on the method of Roman et al. (C) 2015 Elsevier B.V. All rights reserved.