Structure Analysis of Sr₂Nb₂O₇ (010) Surface by X-ray CTR Scattering

Abstract

We have investigated the surface structure of a ferroelectric substance Sr₂Nb₂O₇ in air after cleaving the (010) surface. For this purpose, we examined X-ray crystal truncation rod (CTR) scattering and X-ray reflectivity (XR) at several different temperatures, which yielded the cleaved position unambiguously. After a thermal annealing in air, the cleaved surface were found to be flat on an atomic level, and showed a distinct relaxation where the top Sr cations are pulled to the bulk. Although the strong contraction was indicated, the probability of finding the Sr atom on the Sr-site at the surface was less than 40%. Such an unexpected low Sr-residuary can be accounted for by a condition of the charge-neutralization at the polar (010) surface.