単結晶Ｓｉの高温破壊じん性

Abstract

The fracture toughness (KIC) on the major planes of single crystal silicon was measured by the controlled surface flaw (CSF) and indentation fracture (IF) methods at high temperatures. The KIC values obtained by the CSF method for the surface orientations {100}, {110}, {111} and {112} of silicon up to about 500°C decreased with increasing temperature. In the low temperature region, the linear decrease of KIC for {110}, {111}, and {112}, excepting for {100}, was explained on the basis of an elastic model. The KIC values for {100}, {110}, {111} and {112} planes of silicon increased rapidly over the temperatures of 500, 600, 700 and 800°C, respectively.It was found that the rapid KIC increase for those planes of silicon at the individual critical temperatures was attributable to extensive plastic yielding in the vicinity of the crack tips relating the Schmid factor and numbers of slip systems for each planes. The KIC values obtained by the IF method in the range from 400 to 600°C were larger than those obtained by the CSF method for all planes. The trend of increase in KIC values by the former method in the high temperature region agreed with that by the later method.