Mechanical properties of layered InSe and GaSe single crystals

The mechanical properties of InSe and GaSe single crystals have been studied by means of nanoindentation tests. Both bulk crystals are well ordered and present a predominant gamma -type interlayer stacking sequence as determined by x-ray diffraction and transmission electron microscopy measurements. The course of plastic deformation induced in the crystals by application of a definite shear stress through the penetration of a Berkovich tip indicates that the deformation occurs predominantly by pop-in events along easy slip directions having a fairly elastic character between displacements. Hardness anisotropy along crystal axes is clearly seen and the measured elastic modulus presents a discrepancy smaller than 5% in comparison with theoretical calculations performed using previous experimental values of the elastic constants. (C) 2002 American Institute of Physics.