Phonon dynamics of the Sn/Ge(111)-(3 × 3) surface

• Published in: Applied surface science Vol. 237; no. 1-4; pp. 86 - 92
• Main Authors: Farías, D., Kamiński, W., Lobo, J., Ortega, J., Hulpke, E., Pérez, R., Flores, F., Michel, E.G.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.10.2004; Elsevier Science
• Subjects: Condensed matter: structure, mechanical and thermal properties; DFT–GGA; Exact sciences and technology; Lattice dynamics; Phase transitions and critical phenomena; Phonon; Phonon states and bands, normal modes, and phonon dispersion; Phonons and vibrations in crystal lattices; Phonons-low-dimensional structures; Physics; Solid surfaces and solid-solid interfaces; Surface and interface dynamics and vibrations; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Phase transitions and critical phenomena; DFT–GGA; 68.35.Rh; 68.35.Ja; 71.15.Nc; Phonon; 73.20-r; Phonons-low-dimensional structures; 71.15.Ap; Surface and interface dynamics and vibrations; 71.15.Ap Phase transitions and critical phenomena; Theoretical study; Experimental study; Phonon dispersion; DFT-GGA; Tin; Density functional method; Ab initio calculations; Atom scattering; Surface phonons
• DOI: 10.1016/j.apsusc.2004.06.150
• ISSN: 0169-4332

We present a theoretical and experimental study on the phonon dynamics of the low-temperature Sn/Ge(111)-(3 × 3) structure. High-resolution helium atom scattering (HAS) data show that, besides the Rayleigh wave, there are three surface phonon branches with low dispersion related to the (3 × 3) surface phase. Their energies are approximately 6.5, 4, and 3meV at the Γ¯ point. In addition, we detect phonon peaks in the Q range 0.4–0.5Å−1 at ~2meV, which correspond to (3 × 3) folding of the Rayleigh wave. Ab initio DFT–GGA total energy calculations have been performed to determine the frequencies associated with the vertical displacements of the three Sn atoms in the unit cell. The values obtained are in good agreement with the experiment.