Molecular effect in semiconductors under heavy-ion bombardment: Quantitative approach based on the concept of nonlinear displacement spikes

A model is developed which is able to describe depth profiles of the efficiency of the molecular effect in damage accumulation in semiconductors under heavy atomic and molecular ion bombardment. In the model, it is assumed that completely disordered zones form due to a catastrophic collapse of the crystalline lattice into an amorphous state when the disorder level within a collision cascade exceeds some critical value f_c. Rather low values of f_c are obtained for this spontaneous crystalline-amorphous transition within dense collision cascades produced in Si by heavy ions. Physical mechanisms responsible for such low values of f_c are discussed.