ANGLE-RESOLVED PHOTOEMISSION-STUDY OF OXYGEN-INDUCED C(2 X 4) STRUCTURE ON PD(110)

Angle-resolved photoemission spectra have been measured for the oxygen-induced c(2 X 4) structure on Pd(110). Some of the c(2 X 4)-related states are identified in the range of binding energy from -6 eV to E(F). In particular, the oxygen 2p(z)-derived bonding state and its antibonding counterpart are found to show considerable dispersion of approximately 1 eV with k(parallel-to) in the [110BAR] direction, while there is no measurable dispersion in the [001BAR] direction. This highly anisotropic dispersion suggests the oxygen and surface palladium atoms to form one-dimensional chains along the [110BAR] direction. Surface band structures are calculated for possible structural models using the tight-binding approximation. The zig-zag Pd-O chain model reproduces well the experimental result and is consistent with the coverage dependence of the low energy electron diffraction patterns.