Surface photovoltage spectroscopy in a Kelvin probe force microscope under ultrahigh vacuum.

Surface photovoltage (SPV) spectroscopy is a common method for optoelectronic semiconductor characterization. Kelvin probe force microscopy has developed into a widely used tool for nanoscale characterization of semiconductors, metals, and insulators. We present here a setup for the measurement of local SPV spectra in a Kelvin probe force microscope operated under ultrahigh vacuum conditions. The atomic force microscope tip can be placed to any desired position with nanometer precision and the SPV can then be recorded as a function of the wavelength of the illuminating light. We introduce the realization of the setup and present the SPV spectra on two test systems, an epitaxially grown GaAs/CuGaSe(2) junction and a Zn-doped CuInS(2) polycrystalline thin film.