Amorphization and stress in ion-implanted crystalline solids

Abstract

The model of amorphization of crystals induced by ion irradiation is considered. The model describes two stages of the amorphization, the generation of primary defects by collision cascades and the collapse of crystalline regions, which begins when the concentration of the primary defects reaches about 10%. Due to the colapse of crystalline regions, the total defect concentration increases up to about 80% for rather small increment of the fluence Φ. The defect concentration and the integral stress were calculated theoretically for the silicon samples subjected to irradiation with light, average, and heavy mass ions. The integral stress was analysed as the sum S = Sd+Sion, where the Sd and Sion terms correspond to the stresses due to point defects and implanted ions, respectively. At low fluences, Φ Φa, the term Sd considerably decreases and the Sion term dominates the integral stress. In this Φ region, the stress saturates to the constant value, which is larger for the lighter ions and smaller for the heavier ones.