Recently, a number of scanning probe microscopy techniques have emerged that can provide more direct and revealing information of surfaces. In addition to the imaging at higher resolution, AFM is also capable of providing a general understanding of the local material properties of the heterogeneous samples Sultan and McGarry 1973; Kinloch et al., 1983; Mélé et al., 2002; Paredes et al., 2005; De Wolf et al., 2001