X-ray crystal-truncation-rod analysis of untwinned YBa2Cu3O7- delta single crystals: The growth-termination plane.

Abstract

Crystal truncation rods (CTR's), or x-ray scattering from a terminated surface of a three-dimensional single crystal, were measured for untwinned single crystals of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$. An expression for the intensity along the CTR's, which may be directly applied to a structure with a complicated unit cell, was derived from a Bloch wave expansion of the electron density. Data analysis using this expression indicates that the most probable metal-containing layer at the terminating surface of a flux-grown ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystal is the Y layer.