THE LOCAL ORDER OF AS SITES IN INCREASINGLY AMORPHOUS SI

Our previous work has concentrated on the recrystallisation of amorpho us silicon with temperature and we used XAFS to follow the local order of the dopants (typically As, Ga, etc) to see them change from essent ially 3-fold in the amorphous state to 4-fold in the crystalline state . The main findings were that the silicon matrix recovers before the d opants can adjust their coordination numbers to the crystalline requir ements. We present here investigations in the reverse process, namely, the progressive amorphisation of the crystalline matrix by ion bombar dment. We show the progressive transformation of the dopants local str ucture as the matrix amorphises and show there is no delay in the stru ctural rearrangement.