Application of Channeling to Defect Studies in Crystals

Abstract

ABSTRACTChanneling of fast, light ions in crystals has been widely used as a tool for studying crystal defects. Backscattering yield measurement on ions incident along major axial or planar crystalline directions provides information on the depth distribution of the structural defects in the first few microns. The channeling technique in defect detection is not as sensitive as Transmission Electron Spectroscopy, nor is it accurate in measuring the absolute numbers of defect density. Channeling measurements can give only an indication of the degree of lattice disorder. It is possible to distinguish one type of defect from another by carefully studying the energy dependence of the dechanneling. The dechanneling interpretation is not always unique, and in practice it is difficult to obtain structure information through that method. Despite these negative qualities, channeling is an attractive and unique method in certain defect studies. For example, it is sensitive for studying the lattice location of impurity atoms at substitutional or interstitial sites. Clustering of substitutional impurity atoms will show a displacement of the impurity atoms from lattice sites due to the change of bond distance. Channeling is sensitive for measuring impurity displacement as small as 0.1A°. This has been demonstrated in the study of arsenic clustering formation in Si. Interfacial relaxation and contraction in a multi-layered structure made by molecular beam epitaxy has been detected by dechanneling along various axial directions. Channeling study on surface and interface structures has developed over the past few years. In this paper, I will use examples to illustrate the unique features of the channeling technique and its application to defect studies in single crystals.