Interaction of Oxygen with the Polar HfC(111) Surface: Angle-Resolved Photoemission Study

Abstract

Angle-resolved photoemission spectroscopy utilizing synchrotron radiation has been used to study the adsorption state of oxygen on a HfC(111) surface. Oxygen adsorbs dissociatively on the HfC(111) surface at room temperature forming a (1 × 1) overlayer at the saturation coverage. The two-dimensional band structure of the chemisorption bonding states formed through the hybridization of O 2p and Hf 5d orbitals (O 2p-derived states) is measured for the HfC(111)(1 × 1)-O surface. It is found that the 2pz-derived band is formed in slightly higher binding energy region relative to the 2px-and 2py-derived bands, indicating that the vertical interaction involving the 2pz orbital is slightly more important in the chemisorption bond formation relative to the lateral interaction involving the 2px and 2py orbitals. Hf 4f spectra are measured for the clean and oxygen-covered HfC(111) surfaces, and it is found that the oxidation of the surface Hf atoms to form a Hf oxide does not proceed at room temperature.

Formation of oxide layer on HfC(100) surface studied by photoemission spectroscopy

“…Our previous study on the oxidation of the HfC(111) surface has revealed that the HfC(111) surface is very reactive to O 2 adsorption; O 2 adsorbs dissociatively with the sticking probability of approximately 1 [24]. However, on the (111) surface, the adsorptiom saturates when the (1 × 1) overlayer is completed (2 L), and the oxidation of the substrate below the surface does not occur [24]. It is considered to be due to the fact that the HfC(111) surface is covered with an Hf layer.…”