X-ray measurement of minute lattice strain in perfect silicon crystals

Abstract

The residual strain still present in nearly perfect silicon single crystals has been measured quantitatively by using double crystal topography at high reflexion orders. High quality float zone crystals from different suppliers were found to vary in residual strain from 2 × 10⁻⁸ to 100 × 10⁻⁸. No direct correlation with resistivity or choice of dopant was found for slightly doped crystals. The possible correlation of the local strain variation with the presence of swirls is discussed. The high sensitivity strain measurements are very useful to measure in a quantitative manner the degree of lattice perfection of so-called nearly perfect crystals. The results are already useful for neutron interferometry and, possibly, may become so for microintegration of devices.