A New Method for Nanometer Scale Imaging of Field Emission Current Distribution

A method to measure nanometer-scale distributions of field emission current is proposed where the tip-surface distance is controlled by the constant current STM operation and the emission current from the surface to the tip is measured at a sufficiently high bias voltage for a brief time under the feed back loop open. In the case of a monolayer graphite on Pt(111), where the electronic structure is perturbed by the interlayer interaction, the FE current is observed higher at the sites with lower work functions. On the other hand, in the case of the polycrystalline HfC film, FE current is higher at the grain boundaries, where work function is higher than at the grains. The results suggest that the field emission is not necessarily determined only by the geometrical feature and the work function