Atomic and electronic structures of thin NaCl films grown on a Ge(0 0 1) surface

• Published in: Surface science 2009-07, Vol.603 (13), p.2102-2107
• Main Authors: Tsay, Shiow-Fon, Lin, D.-S.
• Format: Article
• Language: English
• 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; Density functional calculations; Exact sciences and technology; Germanium; Physics; Semiconductor–insulator interfaces; Surface electronic phenomena; Surface structure; Thin film structures
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2009.04.007

Density functional theory (DFT) with LDA and GGA have been employed to study the interface and thin film properties of NaCl on a Ge(0 0 1) surface. The atomic and electronic structures of thin NaCl films from one to ten monolayers were analyzed. The layer adsorption energies show that a quasi-crystalline (0 0 1) fcc NaCl film is built up via a layer-by-layer growth mode with NaCl thickness above 2 ML. Simulated STM images show a well-resolved (1 × 1) NaCl atomic structure for sample bias voltage V s < −2.5 V and the bright protrusions should be assigned to the Cl − ions of the NaCl film. The Ge substrate dimer is reserved and buckled like a clean Ge(0 0 1)- p(2 × 2) surface as the result of weak interface interaction between the dangling bonds coming from valence π states of the Ge substrate and the 3 p states of the interfacial Cl − ion. These results are consistent with the experiments of STM, LEED and EELS.