A model for interpreting measurements of the formation of bombardment-induced disorder (Studies on Bombardment-Induced Disorder, IV)

Abstract

It is well established that ion bombardment of certain solids leads to the formation of a disordered, often amorphous, phase. Though it is not difficult to describe the fractional disordering (F _d) as a function of the depth and of the volume disordered per ion impact, there is still no adequate model which relates F _d, to the fraction of inert gas (F _IB) that would be released during the thermal annealing or chemical dissolution of the disorder. It is shown that an analytically manageable relation between F _d and F _IB can be obtained on the basis of four assumptions, the most critical of which is that each ion impact gives rise to a compact, rather than fragmented, disordered region. This relation is shown to be reasonably well obeyed with Al₂O₃, diamond, and ZrSiO₄, making it possible to estimate both the effective depth of disordering (R _d) and the size of the disordered regions (V _d ^1/3). R _d for 10-keV Kr bombardment is with all three substances roughly 140 A. Likewise, V _d ^1/3 is 14–20 A with Al₂O₃, 13–16 A with diamond, 20–27 A with ZrSiO₄, and thus similar to what is observed using alternative approaches (e.g. electron microscopy) with Al₂O₃, Ge, Si, and ZrSiO₄.