Investigation of Hf Adatom Adsorption on Graphene Using Density Functional Theory Calculations

Abstract

Density functional theory calculations of various atomic species on a graphene sheet are investigated as prototypes for the formation of nanostructures on graphene. These studies discuss the adsorption and migration energy when an adatom is adsorbed on graphene. In this study, we performed calculations regarding the adsorption of Hf atoms on graphene for several different coverages and geometries, because Hf has attracted attention as a buffer layer when a compound is grown on graphene. The calculations were performed for adatoms at three sites having BRIDGE, HOLLOW, or TOP symmetries on 3 × 3 and 2 × 2 supercells for coverages of 0.056, 0.111, 0.167, 0.25, and 0.375. The results indicated that when Hf atoms are adsorbed on the HOLLOW site, the adsorption energy tends to increase, and the subsequent metastable adsorption is a TOP-site adsorption. The most stable structure with a coverage of 0.375 is when two Hf atoms are adsorbed on the TOP site and one Hf atom is adsorbed on the HOLLOW site. Interestingly, the most stable adsorption structure for a coverage of 0.375 is hcp-Hf [0001], the same as that of the surface. [DOI: 10.1380/ejssnt.2012.325]