The temperature dependence of the interaction of oxygen with Pd(111); A study by photoemission and auger spectroscopy

The temperature dependence of the different binding states of oxygen on Pd(111) has been studied using photoemission spectroscopy and Auger spectroscopy. By examining the oxygen 2s binding energies, three distinct states are observed, which are identified as surface chemisorbed oxygen, oxygen incorporated into the first Pd layer, and subsurface oxygen. Changes in the relative oxygen Auger peak heights for 1000 K exposure temperature are explained if the oxygen is assumed to become more negatively charged as it penetrates the Pd surface. A model for the interaction of oxygen with the Pd(111) surface is proposed.