TIP-FORCE INDUCED SURFACE DEFORMATION IN THE LAYERED COMMENSURATE TELLURIDES NBA(X)TE(2) (A=SI, GE) DURING ATOMIC-FORCE MICROSCOPY MEASUREMENTS

The Te-atom surfaces of commensurate layered tellurides NbA(x)Te(2) (A = Si, x = 1/2; A = Ge, x = 1/3, 2/5, 3/7) were examined by atomic force microscopy (AFM) at different applied forces. Although the bulk crystal structures show a negligible height corrugation in the surface Te-atom sheets, the AFM images exhibit dark linear patterns that become strongly pronounced at high applied forces (several hundreds nN). This feature comes about because the tip-sample force interactions induce a surface corrugation according to the local hardness variation of the surface.