Analysis of the HfC(111) surface structure by impact collision ion scattering spectroscopy (ICISS)

Abstract

The structure of the HfC(111) clean surface and the O 2, D 2 adsorption systems at room temperature have been studied by impact collision ion scattering spectroscopy (ICISS). The clean surface exhibits a 1 × 1 low energy electron diffraction (LEED) pattern and no reconstruction occurs. The outermost layer consists of Hf atoms and the space between the first and second layer contracts by 0.18 ± 0.05 A ̊ , which is equal to (13.4 ± 3.7)% of the corresponding bulk value. The oxygen-adsorbed surface has a 1 × 1 structure and the O atom is located on the threefold hollow site, under which a Hf atom of third layer exists. By comparing the ICISS spectra with computer simulations, the distance between the O atom and the surface has been determined at 0.90 ± 0.05 A ̊ (O-Hf bond length = 2.10 ± 0.07 A ̊ ). In case of deuterium, D, the atom is adsorbed on the same site as oxygen and the distance from the surface is 1.36 ± 0.07 A ̊ (D-Hf bond length = 2.33 ± 0.10 A ̊ ). Judging from the distance between the Hf atom and the adsorbates, the Hf-O bond seems to be rather ionic and the Hf-D bond seems covalent.