Ion beam implantation of surface layers

Ion implantation is a method for the direct, controlled introduction of impurities into solids. In ion implantation, a beam of dopant ions is aimed at a target material (the substrate) so that the ions are incident with sufficient energy to become permanently embedded. Because ion implantation is an essentially nonequilibrium process, it allows for the creation of concentration profiles that would be impossible to achieve using equilibrium techniques such as diffusion. The advent of focused ion beam (FIB) systems spawned a host of new applications for ion implantation. The ability to create high-resolution (feature sizes of order 10 nm [1, 2]) doping configurations without the use of a mask allows not only for rapid prototyping, but also for unique devices whose fabrication would not otherwise be feasible. FIB implantation has been used to make a wide variety of experimental devices including low-dimensional transistors, single photon detectors, subwavelength optics, and quantum computers.