Fracture of Silicon and Germanium Induced by Pulsed Electron Irradiation

This paper presents certain preliminary results on the fracture of silicon, germanium and indium antimonide resulting from pulsed electron irradiation. Experimental results show that the rapid absorption of energy can produce brittle fracture in the semiconducting materials silicon, germanium and indium antimonide. Samples were irradiated using the external electron beam from a flash X-ray generator having a peak electron energy of 2.2 Mev and a pulse width of approximately 40 nsec. All irradiations were done at room temperature with the total exposure controlled by an appropriate choice of separation distance between sample and source. Samples of various sizes and geometry were prepared from single crystals of n-type germanium and silicon. Sample orientation was obtained through X-ray diffraction. Surface treatments were varied and included a finish polish and etch. Experimental results on germanium, silicon and indium antimonide have established the fracture threshold for polished and etched bulk material to be approximately 34 cal/g for silicon, about 8.5 cal/g for germanium and 4 cal/ g in indium antimonide. Surface treatment played an important role in the observed fracture level. No dimensional dependence of the fracture threshold was observed using polished and etched bars 1 × 1 mm2 in cross section and having lengths between 1 and 25 mm. The fracture planes in both silicon and germanium were found to be the (111) crystal planes and the (110) planes in indium antimonide.