The Fermi surface of Sn/Ge(111) and Pb/Ge(111)

Abstract

The analysis of the electronic structure and Fermi surface of 0.33 monolayers (ML) of Sn/Ge(111) and Pb/Ge(111) has played an important role in understanding the phase transition from a room-temperature ( √ 3 × √ 3)R30 • reconstruction to a (3 × 3) reconstruction below ∼200 K. Nowadays, the increasing resolution of image-type electron analysers enables us to obtain whole sets of constant-energy surfaces and energy-distribution curves. We review the electronic structure of Sn and Pb on Ge(111) and report highresolution angle-resolved photoemission data for Sn/Ge(111)-(3 × 3) at 110 K. The results exclude nesting or any opening of a gap in the (3 × 3) phase at this temperature. From a comparison with density functional theoretical calculations, we conclude that the results on the electronic structure are only compatible with a (3 × 3) unit cell with one Sn atom displaced upward from the other two.

Structural Origin of the Sn4dCore Level Line Shape inSn/Ge(111)−(3×Tejeda1, Cortés2, Lobo-Checa3 et al. 2008Phys. Rev. Lett.254331View full textAdd to dashboardCite

“…Although the height difference between the two down atoms in the IDA-(3 3) structure is significant, it is always much smaller than the up-down total corrugation, so that a 1U2D description is correct. This is also in agreement with recent Fermi surface studies supporting the 1U2D model [12]. In fact, the observation of this small height difference is only possible in images taken with an excellent vertical and lateral resolution.…”

Low temperature phases of Pb/Si(111) and related surfaces

“…2) do not present any characteristics of an incipient CDW instability. This is a feature common to all the ffiffi ffi 3 p phases [6] and rules out a possible role of electron-phonon interactions in the stabilization of the 3 Â 3 phase in this system as well. On the other hand, recent discoveries on Sn/Ge (1 1 1), open new possibilities for the real ground state phase of this class of systems.…”

“…3  3 low temperature (LT) transition at about 200 K. Sn/Ge(1 1 1) and Pb/Ge(1 1 1) are the prototype systems showing this phenomenology, while Sn/Si(1 1 1), Pb/Si(1 1 1) and even C/Si(1 1 1) present some opposite evidences. In fact, from the experimental point of view, the phase transition is clearly observed in Sn/Ge(1 1 1) and Pb/Ge(1 1 1) [2,3,6], while it is not found in Sn/Si(1 1 1) [7,8] and only recently discovered in Pb/Si(1 1 1) [9][10][11]. In addition, new experimental evidences on the Sn/Ge(1 1 1) surface pose novel interesting questions: in contrast with previous experimental and theoretical results assessing a 3  3 reconstruction with three Sn adatoms in the surface unit cell in the so-called 1Up-2Down configuration, recent X-ray standing wave analysis (XSW) [12] shows a reversed reconstruction, namely 2Up-1Down configuration, while, at lower temperature (T ¼ 30 K) [13] a ffiffi ffi 3 p  ffiffi ffi 3 p R30 ð ffiffi ffi 3 p Þ semiconducting phase is established.…”

Electron correlation and many‐body effects at interfaces on semiconducting substrates

“…A similar transition was observed at 210 K on Sn/Ge(111) 80, where physical properties are similar but the quality of the interface is better 80–82. On Sn/Ge(111), density functional theory (DFT) calculations found a negligible nesting, confirmed also by Fermi surface measurements 83, 84. The CDW was unexplained by a Peierls mechanism 80 and it was necessary to evoke correlation effects 80 and the role of defects 85–88.…”