Absolute Measurement of the (220) Lattice Plane Spacing in a Silicon Crystal

Abstract

The (220) lattice plane spacing of an almost perfect crystal of silicon was measured by means of a combined scanning ($\mathrm{LLL}$) x-ray interferometer and a two-beam optical interferometer. From 170 measurements, a value ${d}_{220}=(192015.560\ifmmode\pm\else\textpm\fi{}0.012)$ fm results in vacuum at 22.50\ifmmode^\circ\else\textdegree\fi{}C. This value is smaller by $1.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}{d}_{220}$ than that reported by Deslattes et al. for another crystal. Generic variabilities of the two crystals account only for a part of this difference.