ELECTROSTATIC FORCES BETWEEN A METALLIC TIP AND SEMICONDUCTOR SURFACES

The Atomic Force Microscope used in resonant models a powerful tool to measure local surface properties : for example, the quantitative anal ysis of the electrical forces induced by the application of an electri cal tension between a conductive microscope tip and a surface in front allows the determination of the tip/surface capacitance and of the lo cal surface work function. However, this analysis needs a well adapted model for each type of surface. In this paper, we calculate, with a s imple geometrical model, the tip-surface interaction for a metallic ti p and a semiconducting surface and we describe its variation with the applied tension and the tip/surface distance. Our results show differe nt kinds of behaviour that we are able to associate with the different semiconductor regimes (accumulation, depletion, inversion). Therefore , it is not possible to describe this tip-surface system as a passive capacitance.