Analysis of onset of dislocation nucleation during nanoindentation and nanoscratching of InP

Abstract

Nanoindentation and nanoscratching of an indium phosphide (InP) semiconductor surface was investigated via contact mechanics. Plastic deformation in InP is known to be caused by the nucleation, propagation, and multiplication of dislocations. Using selective electrochemical dissolution, which reveals dislocations at the semiconductor surface, the load needed to create the first dislocations in indentation and scratching can be determined. The experimental results showed that the load threshold to generate the first dislocations is twice lower in scratching compared to indentation. By modeling the elastic stress fields using contact mechanics based on Hertz's theory, the results during scratching can be related to the friction between the surface and the tip. Moreover, Hertz's model suggests that dislocations nucleate firstly at the surface and then propagate inside the bulk. The dislocation nucleation process explains the pop-in event which is characterized by a sudden extension of the indenter inside the surface during loading.

Emission of partial dislocations in silicon under nanoindentation

“…More precisely, the emission process represents the generation of a dipole of Shockley partial dislocations with Burgers vectors b andÀb, called b-dislocation and (Àb)-dislocation, respectively. 42,43 The b-dislocation of the dipole under consideration here is immobile (it is located at the boundary of the phase transformed zone), whereas the (Àb)-dislocation moves into the bulk of silicon (Fig. 2).…”

“…Based on the experimental results available 13,22,23,26,[38][39][40][41][42] and the above analysis, we can establish the following theoretical model to explore the critical indentation load for the emission of partial dislocations during nanoindentation. The model is illustrated in Fig.…”

“…Then, as the shear stress on some slip planes caused by nanoindentation reaches the critical shear stress for nucleating dislocations, the dislocation will appear or emit. [38][39][40][41] To date, however, no analytical model is available to predict the threshold stress and state of stress of the dislocation initiation in silicon under nanoindentation, [38][39][40][41][42] although a quantitative evaluation of the critical load is vital to the development of damagefree machining of silicon for semiconductor industry.…”

The effect of nanoscratching direction on the plastic deformation and surface morphology of InP crystals

“…A more detailed analysis requires consideration of the crystal nature of the material, namely the slip systems, and more specifically the component of the force along the slip directions. The critical shear stress in the bulk (away from the surface) has been calculated for the elasticplastic case to be 2.5 GPa, 24 and for a pure-plastic case that includes dislocation generation at the surface to be 1.3 GPa. 25 FIG.…”

“…It is of interest to know the dependence of the resolved shear stress on the direction of the applied lateral force. An analysis of the stress fields associated with scratching brittle materials has been reported by Ahn et al 26 The distribution of the maximum shear stress inside the bulk and at the surface of the scratch has been simulated by Wasmer et al 24 We use here a simpler approach by considering the projection cosine of the lateral force in the direction of the displacement (Burgers) vector. In other words, we consider the component of the lateral force along the possible h110i directions associated with elemental plastic events.…”