The science and technology of low-energy ion-surface interactions

Low-energy ion-surface interactions have played a significant role in both the analysis and modification of the near-surface layers of solid materials. From ion scattering spectrometry to eV implantation, the technology of the ion beam or plasma system has played a key role in determining the effectiveness of the processes involved. The development and understanding of the technology required for low-energy ion implantation, ion-beam deposition, ion plating and reactive ion etching has relied heavily on the availability of analytical systems capable of characterising the nature of both the ion beams or plasmas and the surface region of the solid being treated. The present review follows the development of ion beam systems from the low-current analytical beams used for low and medium ion scattering and secondary ion and photon emission through to the high-current machines used for ion implantation and ion beam deposition. The transport concepts used in the latter machines formed the basis of high current, low-energy systems used commercially to produce the ultra-shallow junctions required for the current generation of MOS devices. These developments will be described in the context of the growth in understanding of the beam and plasma physics and the atomic collision processes involved. All the technological developments at Salford were carried out in the course of detailed studies of the atomic collision processes associated with ion trapping and release, ion scattering and sputtering. The results of some of these studies and the ways in which they have contributed to our current understanding of the physics of ion-surface interactions will also be reviewed.