STRAIN ANALYSIS BY X-RAY-DIFFRACTION

This paper describes the importance of measuring the absolute strain l evels in materials for relaxation and composition determination. The g eneral reliance on assumed lattice parameters of materials for interna l reference is shown to create uncertainties. The underlying substrate can be distorted by epitaxy or from surface preparation and can there fore be an unreliable reference. Because of this, absolute strain meas urements are preferable. Two absolute lattice parameter methods are co mpared and a new procedure for precision determination of relaxation d escribed. It was found that the underlying substrate with a relaxing l ayer on top indicated significant distortion that strongly influenced the apparent degree of relaxation. The importance on the most appropri ate reflections used for measuring similar volumes is also discussed. (C) 1998 Elsevier Science S.A.