Ion-beam-induced topography and surface diffusion

Abstract

The development of surface microtexture along with ion-impact-enhanced surface and bulk diffusion processes is important for users of ion beams and plasmas for thin film or material processing. Even in those applications where texturing is not desired, an understanding of the process of texturing will permit proper corrective action when texturing is found to occur. Surface microtexturing produced using ion-beam sputtering and simultaneous deposition of impurities is described both in terms of a simple diffusion model and with regard to detailed studies of the initiation, development, and failure of individual sputter cones. Digital computer calculations are presented which follow surface feature development under sputtering. These calculations appear to confirm the role of ion reflection in the development of cones. A coating associated with the impurity deposition is often observed on individual cones. This coating appears to play a role both in the initial development of cones and in the subsequent evolution of second generation cones in a steady-state process. Surface diffusion, in excess of that expected from thermally activated diffusion alone, has been observed as the ion-beam current density is increased. This impact-enhanced diffusion appears to depend on cooperative effects between multiple ion impacts.