Ion implantation in insulators

The modifications of insulating materials by ion implantation can be of considerable interest for many applications. If ion implantation has considerable potential for changing the properties of insulators, only a few experiments have determined the critical parameters which are important in the behaviour of the implanted layer. As a matter of fact, the ion implantation process is, by its very nature, a non-equilibrium process and, in addition, the injection of charged particles in a lattice determines a concomitant creation of intrinsic lattice defects. These defects are associated with the nuclear part of the energy loss of the particles and sometimes with the electronic one (halide compounds). The characterization of these intrinsic defects and the knowledge of their spatial distribution in the lattice are necessary because the formation or dissolution of phases precipitated in the implanted layer are strongly influenced by point or extended defects.

The main parameters which determine the charge state and site location of the implanted atoms in insulating targets are: ionicity of the chemical bond of the lattice, electronegativity, thermal or radiation enhanced diffusion processes, and intrinsic defects. For heavily implanted insulators, phase changes of compositional type can occur which can lead to strong modifications of the physical properties of the implanted layer. In order to obtain information on the relative extent of the critical parameters of chemical implantation in insulators it is necessary to combine analysis with different techniques such as, nuclear techniques, TEM, ESR, optical spectroscopy, X-ray diffraction at glancing angle, etc.

To illustrate the effects of these parameters, typical experimental results obtained in implanted binary or ternary compounds are reported (alkali halides, silver halides, alkaline earth oxides or fluorides, transition metal oxides, natural minerals, etc.).