Development of ion implantation

The control of surface properties is of paramount importance for a wide range of materials applications, and craftsmen and technologists of all scientific disciplines have battled with problems of corrosion, surface hardness, friction and electrical and optical behaviour for many hundreds of years. Even for the simplest of articles, whether they be knives, bottles or non-stick frying pans, the manufacture of materials which have the desired surface properties is often incompatible with bulk performance, and so there is an emphasis on finding ways to modify surface layers. Processes such as thermal quenching prove effective for hardening steel and glass bottles but lack the finesse which is required for more sophisticated technology. Instead, these use more controllable treatments, including the deposition of surface coatings or diffusion of impurities into the surface layer and, of course, ion implantation.

Historically, ion implantation has generally been the last of the treatments to receive widespread acceptance. The reason for this is that, compared with coating and diffusion treatments, it appeared to require more complex and expensive equipment which was not readily available. Figure 1.1 indicates that implantation systems may come in several levels of complexity. There are those similar to sophisticated laboratory research machines, which have ion sources, pre-acceleration, mass analysis followed by additional acceleration and then the target region. Commercial applications with requirements of uniformity and a large sample throughput may result in sample handling and beam sweeping equipment as complex and expensive as the accelerator.