IRAS OBSERVATIONS OF PHASE-TRANSITIONS AT NI/MO(110) AND CO/MO(110) INTERFACES

Ultra-thin, annealed films of Ni and Co on a Mo(110) surface show structural phase transitions ((8x2) to (7x2) for Ni and pseudomorphic to (8X2) for Co) at Ni and Co coverages of approximately 0.95 and approximately 1.0 ML (I ML = 1.428 X 10(15) atoms cm-2), respectively. These phase transitions are clearly reflected in the CO IR spectra. In addition, the disorder-order transitions of Ni/Mo(110) and Co/Mo(110) that occur upon annealing are also indicated in the corresponding CO IR spectra. The transitions of these ordered and disordered two-dimensional phases appear to occur via an island growth mechanism with expansion at the island edges.