Observation of surface potential at nanometer scale by electrostatic force microscopy (EFM) with large signals

By polarising the tip of an atomic force microscope (AFM) (in non-contact resonant mode) it is possible to detect local variations in the surface potential of nanostructures. These potential variations are detected by measuring the cantilever flexure produced by the applied signal. This information is obtained at the same time as the classic non-contact (AFM) topography. Both sinusoidal and large square signals can be used to achieve this. Several examples of surfaces obtained by molecular Beam epitaxy are given. lnAs growths on GaSb substrata followed by annealing are studied and show partial coverage and islands. These structures present potential variations related (or not) to relief, indicating variations in contact potential and surface composition. For III–V nanostructures, the electrostatic force microscopeʹs resolution is of the order of 100 mV and 10 nm.