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  Leendertz, C. ; Streicher, F.; Lux-Steiner, M.Ch.; Sadewasser, S.: Evaluation of Kelvin probe force microscopy for imaging grain boundaries in chalcopyrite thin films. Applied Physics Letters 89 (2006), p. 113120/1-3

10.1063/1.2354474

Abstract:
In view of the outstanding performance of polycrystalline thin film solar cells on the basis of Cu(In,Ga)Se₂, the electrical activity at grain boundaries currently receives considerable attention. Recently, Kelvin probe force microscopy (KPFM) has been applied to characterize of the properties of individual grain boundaries, observing a drop in the surface potential in many cases. We present finite element simulations of the electrostatic forces to assess the experimental resolution of KPFM. Depending on the tip-sample distance, the observed drop in the work function amounts to only a fraction of the real surface potential drop. The simulations are considered for different grain boundary models and consequences for the quantitative evaluation of experimental results are discussed.