Electron Microscopy of Dislocations and Other Defects in Sapphire and in Silicon Carbide, Thinned by Sputtering

Ion bombardment has been employed as a means of thinning crystals of silicon carbide and sapphire for subsequent investigation with transmission electron microscopy. The procedures employed are described. In sapphire, small specks were found, and these were attributed to clustering at room temperature of defects introduced by the bombardment with ∼ 2 keV argon ions used during thinning. Upon heating to 800 °C, extensive networks of dislocations were formed, and the motion of these dislocations could be followed. Gas bubbles were present after annealing for an hour at 900 °C or above. No dissociation of the dislocations in sapphire was observed, but the Burgers vectors were along the a directions as anticipated. In silicon carbide, wide ribbons of stacking fault were found on the basal planes, and the stacking fault energy was estimated to be 4 erg cm−2 within an order of magnitude.