Plastic deformation of diamond at room temperature

Abstract

POLISHED (101) surfaces of type IIB diamonds have been indented with a Knoop indenter at room temperature. The diamonds were thinned from the opposite side by ion-beam bombardment and the resulting deformation observed and analysed using transmission electron microscopy. For the two orientations of indentation examined so far, it has been found that shear events (probably shear cracks) and dislocations comprise the major part of the deformation. Diamond is usually considered to be a brittle material, easy fracture (cleavage) occurring on {111} planes. Although plastic deformation and dislocation generation (also on {111} planes) have been demonstrated in diamond at 1,800 °C (ref. 1) there has been continuing interest as to whether any plastic flow at all occurs at normal temperatures². Several means of deciding this question have been tried^3–7, but the results are mostly inconclusive. We have indented diamond specimens with a Knoop indentor⁸ and observed the resulting deformation directly using transmission electron microscopy. We report here preliminary results for indentations whose long axes are close to [01] and [010] directions in the (101) surface.