The Sn͞Ge(111) interface has been investigated across the 3 3 3 ! p 3 3 p 3 R30 ± phase transition using core level and valence band photoemission spectroscopies. We find, both above and below the transition, two different components in the Sn 4d core level and a band splitting in the surface state crossing the Fermi energy. Theoretical calculations show that these two effects are due to the existence of two structurally different kinds of Sn atoms that fluctuate at room temperature between two positions and are stabilized in a 3 3 3 structure at low temperature. [S0031-9007(98)

The Cu(111) surface state has been mapped for vicinal surfaces with variable step densities by angleresolved photoemission. Using tunable synchrotron radiation to vary the k dependence perpendicular to the surface, as well as the k k dependence, we find a switch between two qualitatively different regimes at a miscut of 7 ± (17 Å terrace width). For larger miscut angles the step modulation of the wave function dominates, and for smaller miscut angles the terrace modulation dominates. These observations resolve an apparent inconsistency between prior photoemission and STM results.

Antimonene, a novel group 15 two‐dimensional material, is functionalized with a tailormade perylene bisimide through strong van der Waals interactions. The functionalization process leads to a significant quenching of the perylene fluorescence, and surpasses that observed for either graphene or black phosphorus, thus allowing straightforward characterization of the flakes by scanning Raman microscopy. Furthermore, scanning photoelectron microscopy studies and theoretical calculations reveal a remarkable charge‐transfer behavior, being twice that of black phosphorus. Moreover, the excellent stability under environmental conditions of pristine antimonene has been tackled, thus pointing towards the spontaneous formation of a sub‐nanometric oxide passivation layer. DFT calculations revealed that the noncovalent functionalization of antimonene results in a charge‐transfer band gap of 1.1 eV.

We identify and characterize a two-dimensional phase transition in a layer of Sn on Cu͑100͒. The stable phase at room temperature has a ͑3 ͱ 2 ϫ ͱ 2͒R45°structure. Above ϳ360 K, a new phase with ͑ ͱ 2 ϫ ͱ 2͒R45°structure is formed. The high-temperature phase exhibits a quasi-two-dimensional free-electron surface band, with Fermi surface nesting in excellent agreement with the three-times larger periodicity of the low-temperature phase. A momentum-dependent band gap opens along the nested areas of the Fermi surface in the low-temperature phase. The phase transition is a clear experimental confirmation of the role of Fermisurface gapping and nesting in the stabilization of a commensurate two-dimensional phase, which is interpreted as a charge-density wave.

We report an investigation on the properties of 0.33 ML of Sn on Ge(111) at temperatures down to 5 K. Low-energy electron diffraction and scanning tunneling microscopy show that the (3 3) phase formed at 200 K, reverts to a new 3 p 3 p R30 phase below 30 K. The vertical distortion characteristic of the (3 3) phase is lost across the phase transition, which is fully reversible. Angle-resolved photoemission experiments show that, concomitantly with the structural phase transition, a metal-insulator phase transition takes place. The 3 p 3 p R30 ground state is interpreted as the formation of a Mott insulator for a narrow half-filled band in a two-dimensional triangular lattice.