Bragg-case diffraction curves from copper whiskers by the X-ray triple-crystal diffraction method

The surface quality of copper whiskers grown by the hydrogen reduction of cuprous iodide has been investigated by measuring Bragg-case diffraction curves by means of X-ray triple-crystal diffractometry with Cu Kα₁ radiation. The observed half-widths vary from whisker to whisker, probably owing to the existence of a very thin surface layer contaminated with oxygen and/or impurity atoms. When the surface is good in quality, the observed diffraction curves clearly show the asymmetry of the intensity profile and fit well with the convoluted curve calculated with the dynamical theory of X-ray diffraction for a perfect single-crystal. From the half-width of the diffraction curve showing the best fitting with the calculated curve, the f⁰₂₂₀ value has been determined as 16.75 ± 0.08 with a dispersion correction f′ = −2.019, in excellent agreement with the theoretical value 16.76 given by Freeman & Watson [Acta Cryst. (1961), 14, 231–234].