5 - Ion Implantation Studies of Hydrogen in Solids

Abstract

Ion-beam techniques have provided an important new way to study the behavior of hydrogen in solids. In this approach, ion implantation is used for the controlled introduction of hydrogen isotopes, and then ion microanalysis techniques are used to measure the amount and depth profile of near-surface hydrogen and the crystallographic lattice sites it occupies. Hydrogen implantation and ion-beam analysis techniques give rise to certain advantages and differences from other techniques for the study of hydrogen in solids. The controlled introduction of hydrogen by ion implantation allows the behavior of hydrogen to be investigated continuously from the dilute concentration regime up through the very high concentration regime. Other methods of hydrogen introduction, such as diffusion from the gas phase or introduction by electrochemical means, are frequently not subject to such a high degree of control. In addition, because ion implantation is a nonequilibrium process, concentrations in excess of the equilibrium solid solubility can be introduced. Thus, by simultaneously controlling the sample temperature and hydrogen concentration, metastable phases or hydrogen-containing second phases may be formed. Another unique aspect of the implantation studies is that at normal implantation energies, defects are introduced along with the hydrogen atoms because of the lattice displacements produced by the energetic implanted ions.