Atomic structure of the InSb(001)-C(8x2) reconstruction determined by X-ray diffraction

We report a surface X-ray diffraction study of the indium-rich InSb(001)-c(8 x 2) reconstruction, which gives for the first time a detailed picture of the atomic structure. A total of 96 in-plane (hk) reflections were used to determine the structure in the surface plane. The out-of-plane atomic positions were found by measuring along three crystal truncation rods (CTRs) where the total intensity distribution is the result of interference between bulk and surface contributions. The detailed analysis disproves the missing dimer model proposed from earlier PES and STM measurements. It shows that the reconstruction is deeper than the Sb-rich c(4 x 4) and is composed of chains of In atoms running along the [110] axis, separated by pairs of Sb dimers on top of the Sb-terminated bulk. The proposed structure is consistent with recent STM images and represents a significant departure from the models previously suggested for the c(8 x 2) reconstruction on any of the III-V (001) surfaces. (C) 1998 Elsevier Science B.V. All rights reserved.