Room temperature deformation of 6H–SiC single crystals investigated by micropillar compression

Abstract

The room-temperature plastic deformation behavior of 6H–SiC single crystals has been investigated by uniaxial compression of micropillar specimens as a function of crystal orientation and specimen size. Plastic flow is observed even at room temperature by basal and prism slip, latter of which have never been observed in the bulk. The CRSS values for basal and prism slip are as high as above 5 and 6 GPa at the specimen size of 5 μm, respectively, each of which increases with decreasing specimen size, following an inverse power-law relationship with a relatively small power-law exponent of ∼0.10 and ∼0.21, respectively. The CRSS values for basal slip are not virtually affected by the existence of basal dislocations introduced at 1300 °C prior to micropillar compression tests at room temperature. The majority of basal dislocations observed after micropillar compression are perfect (undissociated) screw dislocations, and they are considered to be introduced in the shuffle-set plane during micropillar testing, unlike widely dissociated dislocations introduced in the glide-set plane in the bulk during high-temperature deformation. Prism dislocations are observed also to glide as perfect (undissociated) dislocations and tend to align strongly along their screw orientation. The fracture toughness values are estimated to be 1.37 ± 0.13 and 1.57 ± 0.13 MPa m1/2 by three-point bend tests for chevron-notched single crystalline specimens with a notch plane being parallel to (0001) and {0110} planes, respectively.