Channeling as a means to obtain information on crystal quality and structure

Rutherford Backscattering Spectrometry (RBS) is an analysis technique that uses fast ions like He+ to obtain information about the chemical composition in the surface region. In case of crystalline samples, the ion beam can be aligned with the crystal orientation thereby allowing the ions to penetrate the sample much deeper than in a random direction. This results in a large reduction of the yield of backscattered ions, the so-called channeling dip. Information about crystal quality can be obtained from the width and the depth of the channeling dip. The position of atoms of a certain species in the crystal can de deduced from the yield reduction in various crystal orientations.

In this presentation, the basic principles of channeling are explained. Channeling can be used to obtain information about the position of impurities in a crystal and to assess damage caused by implantation and the quality of the crystal after subsequent annealing. Examples of these types of analysis are presented. Complementary PIXE (Particle Induced X-ray Emission) channeling can be applied to obtain information about elements that have a mass similar to the main elements, which cannot be measured with RBS. An example of PIXE channeling is also presented.