Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 30: 1D Metal Wires on Semiconductors I
O 30.4: Talk
Tuesday, March 8, 2016, 11:30–11:45, S052
Surface vibrational Raman modes of In/Si(111)-(4x1) and (8x2) nanowires — •Stefan Wippermann1, Wolf Gero Schmidt2, Eugen Speiser3, and Norbert Esser3 — 1Max-Planck-Institut für Eisenforschung, Düsseldorf — 2Universität Paderborn, Germany — 3ISAS Berlin, Germany
The ordered array of atomic-scale In nanowires that self-assembles on the Si(111) surface is a prototypical model system for one-dimensional (1D) electronic systems. It exhibits a Peierls-like instability, inducing a reversible phase transition from the metallic (4x1) phase into the insulating (8x2) ground state at TC = 120 K. The detailed nature and mechanism of this metal-insulator (MI) transition is still discussed controversially. We performed a joint first principles and surface vibrational Raman spectroscopy study of the In/Si(111)-(4x1)/(8x2) surfaces’ vibrational properties. The measured phonons are assigned to characteristic modes of the quasi-1D In nanowires, employing density functional theory calculations and symmetry considerations. Both the (4x1) and (8x2) phases exhibit a distinct set of phonon modes. The observed strong modifications in the Raman spectra of the (8x2) phase are consistent with a symmetric quadrupling of the surface elementary cell and confirm characteristic structural changes at the surface. Funding from DFG FOR1700 is gratefully acknowledged.