Measurement of the local density of states on a metal surface: Scanning tunneling spectroscopic imaging of Au(111)

We describe a method for measurement of the local density of states on metals with the scanning tunneling microscope and apply it to the study of the sp-gap surface state on Au(111). Local surface state peak intensity changes are found to correlate with surface features. Spectroscopic images of the surfaces are produced. The surface state intensity is substantially reduced at step edges as compared to the value for large terraces. A change in the intensity by a factor of 2 over the 23×(3)1/2 reconstruction unit cell is also observed. These effects are attributed to a spatial variation of the surface state intensity with the local potential. Upward shifts of the surface state energy have also been observed on narrow terraces, however more detailed measurements are necessary to understand this effect.