Observation of a Tamm-Type State onCu0.9Al0.1(100) Surface: Disorder Effects and Bulk Electronic Structure of an Alloy

The electronic structure of a C${\mathrm{U}}_{0.9}$ ${\mathrm{Al}}_{0.1}$(100) single crystal has been studied with use of an angle-resolved photoemission technique. An intrinsic Tamm-type surface state is found to exist in the disordered alloy. The linewidth of the surface state is analyzed to deduce the disorder-induced smearing of energy levels. These and other experimental results are discussed in terms of the computed band structure of the alloy on the basis of coherent-potential approximation applied to a realistic muffin-tin Hamiltonian.