THERMAL-STABILITY OF OXIDIZED LA ON PD(100)

We have investigated the thermal stability of oxidized La and Al on Pd (100) by Auger electron spectroscopy measurements carried out under ul trahigh vacuum conditions. The oxidized metal layers with varying cove rages of La and Al were examined at increasing temperatures in order t o follow the removal of oxygen from the surface. For submonolayer La c overages the oxygen was removed at temperatures in the range of 625-85 0 K. The temperature at which the oxygen was removed from the oxidized La increased as the coverage was increased. For similar coverages of Al on Pd the oxygen removal occurred at relatively higher temperatures . Oxygen removal from thin layers of Al on Pd(100) was accompanied by depletion of Al from the surface, whereas in the case of La a stable m etallic layer remained on the surface.