NANOSCALE CHARACTERIZATION OF SEMICONDUCTOR SURFACES BY SPATIALLY-RESOLVED PHOTOCURRENT MEASUREMENTS

A method based on scanning tunneling microscopy has been developed to measure spatially resolved primary photocurrents together with the top ographical image. As model semiconductors n- and p-type WSe2-monocryst als have been used. The system consisting of metal tip, gap and semico nductor sample behaves as a classical metal-insulator-semiconductor (M IS) solar cell. The resolution achieved in the photocurrent image is a t least 1 nm. In order to demonstrate the technique, the sur-faces of clean n- and p-type WSe2 samples have been investigated. The method ha s been extended to analyze metal modified semiconductor surfaces and s ome of these results are shown here.