The surface states (∼2eV below EF), which originated mainly from the dangling bonds of boron atoms on the clean (100) surface, disappeared at an oxygen exposure of ∼1.4L. At the same exposure, an oxygen sticking-coefficient had a maximum value of ∼1.0. A change in the work function due to oxygen adsorption increased linearly with increasing surface oxygen and changed its slope at the above exposure. At a low oxygen-exposure of ∼0.38L, the first peak appeared at ∼6.6eV below ef in the UPS spectra. A second overlapping oxygen peak at ∼6.0eV below EF in the UPS spectra, which grew at around lL and overcame the first peak, shifted to the low binding-energy side above ∼1.4L. The (1 x 1) LEED pattern did not disappear up to an oxygen exposure of several hundreds Langmuir. It was suggested that the results suppored the presence of more than two adsorption states. The results were principally interpreted on the basis of two kinds of chemisorption sites; one being a boron site, and another a lanthanum site.

Oxygen Adsorption on the LaB6(100) Surface Studied by UPS and LEED. Nishitani, R., Kawai, S., Iwasaki, H., Nakamura, S., Aono, M., Tanaka, T.: Surface Science, 1980, 92[1], 191-200