Tunneling spectra at terrace boundaries on the bismuth surface
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C PROPERTIES OF SOLIDS
Tunneling Spectra at Terrace Boundaries on the Bismuth Surface V. S. Edelman Kapitza Institute for Physical Problems, Russian Academy of Sciences, ul. Kosygina 2, Moscow, 119334 Russia e-mail: [email protected] Received December 25, 2007
Abstract—The scanning tunneling spectra of the trigonal bismuth surface are measured in the vicinity of the boundaries of terraces with a diatomic height. It is found that the tunneling spectrum of the planar surface begins to transform at a distance of 2–3 nm from the terrace boundaries, specific features that are characteristic of the planar surface far from the terrace boundaries disappear, and new peaks in the density of states are observed. An analysis of the behavior of the current–voltage characteristics has revealed that one-dimensional electronic systems with a width of the order of an interatomic distance with their own individual spectra are formed at the ends of the rows of the atomic planes. PACS numbers: 73.20.At, 73.20.-r DOI: 10.1134/S1063776108080098
1. INTRODUCTION The electronic properties of bismuth have been investigated over many decades. The energy spectrum of conduction electrons in the bulk of this material has been studied in sufficient detail (see the review [1]). Significant advances have been made in calculating the band structure [2]. The results of these calculations in the most sensitive region, i.e., in the vicinity of the Fermi surface, are in remarkable agreement with experimental data, which requires the accuracy in calculating the energy at the level of a millielectronvolt. Considerable progress has been achieved in the study of surface states. In particular, the investigation of two atomic faces, namely, the trigonal (111) surface (perpendicular to the Γ–T direction in the traditional notation [2]) and the “pseudotrigonal” twin surface (perpendicular to one of the three equivalent Γ–L directions), which coexist with the trigonal surface on a cleavage of the bismuth crystal, was performed using scanning tunneling spectroscopy in [3]. It was shown that, at the surface, there exist two-dimensional electronic states with the characteristics dependent on the surface orientation. In a number of works (see [4–7] and references therein), three bismuth faces, (111), (110), and (100), were examined by angle-resolved photoelectron spectroscopy. In those studies, reliable data were obtained on the density of two-dimensional states near the Fermi level and their spectra were calculated theoretically. According to the results of the aforementioned works, the two-dimensional character of surface states with a density considerably higher than the anomalously low density of conduction electrons in the bulk of bismuth can be considered to be reliably established experimentally [1]. The formation of these states is associated with the violation of the translational sym-
metry of the crystal because of the presence of a free surface. This inference is confirmed by the calculations performed in [5–7], which somewhat differ in both the
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