NANOSCALE PHOTOCURRENT VARIATIONS AT METAL-MODIFIED SEMICONDUCTOR SURFACES

The photocurrents measured by a scanning tunneling microscope have bee n used to analyze the electronic properties of nanoscale-modified WSe2 semiconductor surfaces. On uncovered crystals in ambient air, space c harges along steps can be analyzed. On copper-modified semiconductor s urfaces, the space charge zones around pulse-deposited metal particles and their dependence on the size of the metal particle can be determi ned and provide a first direct proof of size-dependent barrier heights of nanosized Schottky contacts. Also, the time evolution of the elect ronic properties of a metal-modified WSe2 surface under corrosion cond itions was followed by photocurrent measurements. By combination of ph otocurrent measurements and local current/voltage curves, the influenc e of recombination and of charges on the photocurrent can be separated .