Reflection absorption infra-red spectroscopy and high-resolution electron energy loss spectroscopy were used to study the adsorption of oxygen on the (100) and (111) surfaces. Exposure of the surface at temperatures of 95K and above to O2 produced atomic oxygen on the surface and yielded vibrational peaks in good agreement with those observed in previous high-resolution electron energy loss spectroscopy studies. On the La-terminated (100) surface, reflection absorption infra-red spectroscopy peaks corresponded to vibrations of the boron lattice that gained intensity due to a decrease in the screening of surface dipoles that accompanied oxygen adsorption. A sharp peak at ∼ 734/cm in the high-resolution electron energy loss spectroscopy spectrum exhibited isotopic splitting with reflection absorption infra-red spectroscopy into two components at 717 and 740/cm, with full widths at half maximum of only 12/cm. The sharpness of this mode was consistent with its interpretation as a surface phonon that was well separated from both the bulk phonons and other surface phonons. On the boron-terminated (111) surface, broad and weak features were assigned to both vibrations of the boron lattice and of boron oxide. On the (100) surface, oxygen blocked the adsorption sites for CO, and adsorbed CO prevented the dissociative adsorption of O2.

Vibrational Spectroscopy of Oxygen on the (100) and (111) Surfaces of Lanthanum Hexaboride. Yorisaki, T., Tillekaratne, A., Moriya, Y., Oshima, C., Otani, S., Trenary, M.: Surface Science, 2010, 604[13-14], 1202-7