Electronic structure of Pd thin films on the Al(110) surface

The electronic structure of thin epitaxial Pd films on Al(110) was studied as part of an investigation of the role of the substrate in modifying the electronic structure of supported thin metallic films. Ultraviolet photoemission spectroscopy was used to monitor the development of the Pd d bands as a function of overlayer thickness. Auger electron spectroscopy and low‐energy electron diffraction were used to characterize the structure of the overlayer. For submonolayer coverage of Pd a narrow band of Pd‐derived d states is observed 4.8 eV below the Fermi level E_F. This band shifts to lower binding energy and broadens into a bulklike Pd density of states with increasing Pd coverage. A model for the electronic origin of this behavior is discussed. In some respects the Pd monolayer on Al(110) resembles the theoretical ideal of a free, unsupported monolayer, in contrast with the case for Pd on various noble and transition‐metal substrates, and thus provides a means of further probing the nature of substrate–overlayer interactions in bimetallic thin‐film interfaces.