Measuring and modifying the electric surface potential distribution on a nanometre scale: a powerful tool in science and technology

Abstract

The combination of atomic force microscopy (AFM) and Kelvin probe technology is a powerful tool to obtain high-resolution maps of the electric surface potential distribution on conducting and non-conducting samples. We show that potential maps of composite metal films and semiconductors show a clear chemical contrast and can be used to differentiate between different materials with a lateral resolution of a few 10 nm. Because AFM tips are not point-like structures, we establish a simple model to correlate the measured quantities with the true surface potential distribution, and compare numerical simulations of the three-dimensional tip-specimen model with experimental data from test structures. For the first time, we combine the electrostatic surface potential and the topography data to derive the local electrostatic field strength on active transistors. Using suitable substrates, trapped surface charges can be generated by applying short voltage pulses between the tip and the sample surface. These surface charges can be detected in the electric surface potential image and might be used as bits in new data storage systems or as target sites in self-assembly processes.