Mechanical characteristics of mercury cadmium telluride (HgCdTe or MCT) single crystals were investigated using microindentation, nanoindentation, nanoscratching, and in situ atomic force microscopy. All the scratched surfaces of polished MCT wafers at nano-scale exhibit plastic deformation, which is different from brittle nature at macro-scale. All the loading curves of nanoindentation agree well, when the normal loads varies from 1 to 8 mN. The elastic modulus is kept constant approximately at 50 GPa with the indentation depth varying from 200 to 800 nm. The hardness is remained constant basically at 0.35 GPa, as the indentation depth ranges from 2 to 15 mu m. Friction coefficient is retained basically constant, despite of the increasing of applied normal load varying from 1000 to 5000 mu N for nanoscratching. Size effect is observed for the nanohardness during nanoindentation, which is addressed using indentation curvature. The simulated results of size effect are consistent with those found experimentally. (C) 2012 Elsevier B. V. All rights reserved.