The effect of the measuring tip and image reconstruction

In all electrostatic force-based microscopy types, the tip has a profound effect on the measured image because the measured forces are long range. In this chapter, we review most of the important literature devoted to this subject in the last two decades. It is shown that the combined effect of the cantilever, the tip cone and the tip apex is well understood for both conducting and semiconducting surfaces. In KPFM measurements conducted in air, the lateral resolution is in the range of 20-50 nm, but the measured potential is reduced by almost an order of magnitude relative to the theoretical value. In measurements conducted under UHV conditions the resolution is improved to around 10 nm, but the value of themeasured potential is still significantly affected by the cantilever. In the second part, it is shown that today KPFMimages can be reconstructed, using convolution to overcome the effect of the measuring tip and to give the actual sample surface potential. In addition, it is found that the exact tip apex shape is not an important factor in KPFM measurements conducted at tip-sample distances larger than 1.5 nm.