Fermi surface and electronic structure of Pb/Ge(111)

Abstract

The electronic structure of Pb/Ge͑111͒ has been probed along the temperature-induced phase transition ␣ Ϫͱ3ϫͱ3R30°⇒3ϫ3 using angle-resolved photoemission. The ␣Ϫͱ3ϫͱ3R30°phase is metallic due to the existence of a half-filled, dispersing surface band. The 3ϫ3 phase is characterized by the appearance of an additional surface band with 3ϫ3 periodicity, whose role in the phase transition is discussed. The Fermisurface topology of the ␣Ϫͱ3ϫͱ3R30°phase has been probed using angle-resolved photoemission. Its shape is undulated, and it resembles strongly the theoretical prediction, with a Fermi momentum of 0.31 Å Ϫ1 along ⌫K directions and 0.40 Å Ϫ1 along ⌫M directions. These values were determined from different experimental methods, and agree with the values needed for a perfect 3ϫ3 nesting. However, the Fermi surface exhibits no large flat areas suitable for electronic nesting.

Nature of the Low-Temperature3×3Surface Phase of Pb/Ge(111)

“…Second, valence-band photoemission results [7][8][9] do not support the fact that electron correlation plays a major role in 3 3 3 phases. The surface valence bands at low temperature (LT) are split [7], in disagreement with theoretical calculations [2]. Core-level photoemission for Sn͞Ge(111) indicates the existence of two kinds of Sn atoms in the 3 3 3 phase [8,9].…”

“…First, the experimental Fermi surface for Pb͞Ge(111) exhibits no significant nesting [7], a crucial point in the theoretical model proposed in Ref. [2].…”

Dispersive resonance bands within the space-charge layer of a metal-semiconductor junction

“…In [10,[14][15][16][17][18]. However, at the first sight, those bands resemble the bulk hole band edges of Ge.…”

Fermi surfaces of surface states on Si(111)-Ag, Au

“…The states near E F are particularly interesting because they determine most electronic properties, such as conductivity, superconductivity, magnetism, and charge density waves. Recent reports include the effects of charge density waves [1][2][3], a two-dimensional plasmon in a metallic surface-state band [4], increased surface conductivity via adatom doping [5], and metallic umklapp bands arising from a discommensurate overlayer [6]. In particular, surface conductivity is receiving increased interest with the arrival of sophisticated micro-probes, such as 4-point STM probes [7][8][9][10][11].…”