AVERAGE ENERGY DEPOSITED PER ATOM - A UNIVERSAL PARAMETER FOR DESCRIBING ION-ASSISTED FILM GROWTH

The average energy deposited per atom, [E(d)] = E(i)(J(i)/J(Me)), where E(i) is the ion energy and J(i)/J(Me) is the ratio of the accelerated-ion to deposited-thermal-particle fluxes incident at the growing film, has been shown to be one of a set of parameters useful for describing the effects of low-energy ion irradiation on film microstructure during ion-assisted deposition. Recently, however, [E(d)] has often been treated as if it were a fundamental, or universal, parameter. We have carried out experiments in which E(i) (20-100 eV) and J(i)/J(Me) (1-10) were varied independently during the deposition, at constant temperature, of polycrystalline Ti0.5Al0.5N films onto amorphous SiO2 substrates by ultrahigh vacuum reactive magnetron sputtering in pure nitrogen. Ion-irradiation-induced changes in film microstructure, texture, phase composition, and nitrogen-to-metal ratio were found to follow distinctly different mechanistic pathways depending upon whether E(i) or J(i)/J(Me) was varied, resulting in quite different properties for the same value of [E(d)]. Thus, [E(d)] is clearly not a universal parameter.