ION-BEAM MIXING IN INSULATOR SUBSTRATES

Studies of ion beam mixing involving insulator substrates is reviewed with an emphasis on thermodynamical and thermochemical considerations. Such studies generally have employed the bi-layer configuration of metal/insulator combinations. There is little evidence for long-range material transport. In the case of sapphire (single crystal Al2O3) substrates, only recoil mixing has been detected for both metal and oxide films irradiated at room temperature. ''Demixing'' of recoil-implanted cations is indicated at temperatures of 825-900-degrees-C. Agglomeration of non-wetting metal films suggests that surface diffusion occurs under the influence of the ion beam. Ballistic mixing has been reported for metal films on SiC, Si3N4 and SiO2. Ion beam-induced reactions are observed at the interfaces for systems in which the enthalpy of reaction is favorable. There is evidence that chemical effects in the cascade mixing regime determine the phases present in the mixed zone.