Graphene on amorphous HfO2 surface: An ab initio investigation

The energetic stability, electronic, and structural properties of graphene adsorbed on the amorphous HfO2 surface (G/HfO2) have been examined through ab initio theoretical investigations. We have considered the graphene adsorption on (i) defect-free (pristine) and defective HfO2 surfaces, (ii) oxygen vacancy, and (iii) interstitial oxygen atoms. We find that the formation of G/HfO2 is an exothermic process, ruled by van der Waals interactions. In (i) and (iii) there is no net charge transfer between the graphene and the HfO2 surface. In contrast, upon the presence of oxygen vacancy, the adsorbed graphene sheet becomes n-type doped, due to a donor level lying above the Dirac point of the graphene. The absence of G-HfO2 chemical bonds has been maintained, however, the graphene adsorption energy increases when compared with (i) and (iii). Finally, in (ii) we find that HfO2 surface potential becomes more inhomogeneous, strengthening the formation of electron-and hole-rich regions on the graphene sheet. DOI: 10.1103/PhysRevB.87.165307