4. Near-field probes

Scanning probe microscopes, developed since the 1980s, have in common the use of an extremely fine tip brought close to a surface, whose position is scanned along the surface to obtain a two-dimensional mapping of a specific property related to the tip-surface interaction (figure 9 , ). This property may be a tunnel current between an electrically polarized tip and a conductive surface (in the case of STM), or a force between the tip and the surface (in the case of AFM). These techniques have recently made it possible...