The structure and lattice dynamics of RbBr(1 0 0) and RbI(1 0 0) single crystal surfaces: A tensor low energy electron diffraction analysis

• Published in: Surface science Vol. 602; no. 17; pp. 2943 - 2948
• Main Authors: Härtel, S., Vogt, J., Weiss, H.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.09.2008; Amsterdam Elsevier Science; New York, NY
• Subjects: Alkali halides; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Low energy electron diffraction (LEED); Low index single crystal surfaces; Physics; Surface relaxation and reconstruction; Vibrational amplitudes; Alkali halides; Low energy electron diffraction (LEED); Surface relaxation and reconstruction; Vibrational amplitudes; Low index single crystal surfaces; Surface reconstruction; Monocrystals; Lattice dynamics; LEED; Structure relaxation; Surface structure
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2008.07.022

The structure and lattice dynamics of RbBr(1 0 0) and RbI(1 0 0) single crystal surfaces cleaved under UHV conditions were investigated by means of low energy electron diffraction (LEED) at temperatures of 156 K and 183 K, respectively. Since RbBr and RbI are insulators the experiments were carried out with a microchannel plate LEED system at very low primary currents (∼5 nA). For both materials four different diffraction orders could be observed. Diffraction patterns were recorded over an energy range from 30 eV to 220 eV in increments of 2 eV and I( V) curves for each spot were extracted. The I( V) curves were analyzed using the tensor LEED approach. For both alkali halide substrates surface structures of (1 × 1) periodicity close to the truncated bulk structure were found. For RbBr, the first interlayer distance is reduced by about 2.2%, where the Rb + cations in the topmost layer are shifted inwards by 0.06(3) Å, and the anions also exhibit an inward shift which is however smaller (0.04(3) Å). The root mean square vibrational amplitudes are enlarged by a factor of 1.3 for Rb + and 1.25 for Br −, respectively. For RbI(1 0 0) the cations of the topmost layer are shifted inwards by 0.07(3) Å and the anions outwards by 0.02(1) Å. The vibrational amplitudes of the ions are not enlarged as for RbBr but close to the corresponding bulk values.