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Abstract

The electronic structure of NiAl(110) is measured with scanning tunneling spectroscopy at a temperature of 4 K. Reciprocal space images of surface states are obtained by Fourier transformation (FT) of wave patterns created by defects in differential conductance images. Each surface state exhibits a different wave vector pattern in 2-dimensional k-space. Surface states with strong s–p character exhibit contours distributed uniformly in all directions over most of their energy range, while states with d character exhibit strongly directional patterns. For these states, the dispersion is measured and compare favorably with results from photoemission experiments and with theoretical calculations. An indication of a strong interaction between sp- and d-surface states was found from both the Fourier transformed conductance images and their dispersion behaviors. We put forward some arguments to assign one of the FT image features to the Σ₂ (d_xy character) surface state, which is dipole forbidden in photoemission.