Localized states at metal-metal interfaces: An inverse photoemission study of Pd/Nb(110)

We present the results of experimental and theoretical investigations of the Pd/Nb(110) interface. In the experiment we identify an interface resonance which clearly displays the required two-dimensional character of such a state. We further show that it is derived from a surface resonance present on the bare niobium. The presence of the Pd overlayer serves to localize and increase the surface character of this state rather than quenching it. The theoretical calculations support the identification of this state as an interface state and further indicate that its intensity reflects the strength of the interface bond