Monte Carlo simulations of the effects of thin layers of dislocation loops on dechannelling and backscattering in a silicon crystal

The focus of this work is on the superficial disordered layers produced by the current silicon technology and an attempt is made of offering a realistic description of the RES response when applied to their detection. To this purpose, a Monte Carlo (MC) simulation method is used to describe scattering events of He+ ions, with energy E in the sub-MeV range, channelled along the (100) axis of a defective silicon crystal. Two defective structures have been investigated. One is a 'model' isolated defect and it is used to illustrate general properties of dechannelling and backscattering. The second one is a realistic defective structure formed by a buried layer of circular dislocation loops. In both cases, a critical dependence of the backscattering yield Y-bs On the depth of the defects D-p is observed. Also an energy dependence of the type Y-bs similar to E-m has been identified. The value of m, which is around 1, significantly changes with D-p and E. The effect of other structural parameters, apart from D-p, is weak and in order to extract their values from experiments a comparison with an MC simulation would be needed. (C) 2000 Elsevier Science B.V. All rights reserved.