ANGLE-RESOLVED PHOTOEMISSION OF OXYGEN CHEMISORBED NI(110) SURFACES -2X1-O(1 2 ML) AND 3X1-O(2/3 ML)/

The oxygen-induced (2 x 1), (3 x 1) surfaces on Ni(110) with 1/2, 2/3 ML oxygen chemisorbed, were investigated by angle resolved ultraviolet photoemission spectroscopy. The results on the (2 x 1)surface were in good accord with a previous report. The oxygen derived Op(x) state wa s observed to split from the Op(y), Op(z) states and the splitting ene rgy increased from (2 x 1) to (3 x 1) surfaces, owing to the interacti on between adjacent Ni-O chains. Tight-binding calculations were made successfully to reproduce the dispersion of the oxygen derived energy bands of both surfaces. The O-O interaction was found to make a consid erable contribution to the electronic structure of the (3 x 1) surface . Another (2 x 1) surface was discovered when oxygen was exposed of mo re than 10 L with the substrate temperature at 430 degrees C. It was f ound that this high-exposure (2 x 1) surface was apparently identical with the low-exposure (2 x 1) surface.