Surface waves on NiAl(110)

We have investigated the electronic structure of the (110) surface of the NiAl ordered alloy by a combination of scanning tunneling microscopy (STM) and density functional theory band-structure calculations. We present STM images of standing waves on NiAl(110), at both room temperature and 140 K. By Fourier transforming the STM images we obtain an anisotropic surface Fermi contour containing contributions from waves with two different k vectors. Based on band-structure calculations, the origin of the two standing waves has been assigned to a surface state and to the edge of the projected bulk band.