Quasi one-dimensional Ag nanostructures on Si(331)–(12 × 1)

We report on the deposition of sub-monolayer Ag on the Si(331)–(12 × 1) surface. The growth of one-dimensional Ag nanostructures is observed by means of low- temperature scanning tunneling microscopy and low energy electron diffraction. We find that the deposited Ag is organized in nanostructures consistently taking “sawtooth” shapes. While the structures are not perfectly organized, their back edges are atomically straight. The limitations of this system in terms of faceting are also discussed

A new structural model for the Si(331)-(12x1) reconstruction

A new structural model for the Si(331)-(12x1) reconstruction is proposed. Based on scanning tunneling microscopy images of unprecedented resolution, low-energy electron diffraction data, and first-principles total-energy calculations, we demonstrate that the reconstructed Si(331) surface shares the same elementary building blocks as the Si(110)-(16x2) surface, establishing the pentamer as a universal building block for complex silicon surface reconstructions

Elementary structural building blocks encountered in silicon surface reconstructions

Driven by the reduction of dangling bonds and the minimization of surface stress, reconstruction of silicon surfaces leads to a striking diversity of outcomes. Despite this variety even very elaborate structures are generally comprised of a small number of structural building blocks. We here identify important elementary building blocks and discuss their integration into the structural models as well as their impact on the electronic structure of the surface

Excited states at interfaces of a metal-supported ultrathin oxide film

We report layer-resolved measurements of the unoccupied electronic structure of ultrathin MgO films grown on Ag(001). The metal-induced gap states at the metal/oxide interface, the oxide band gap, and a surface core exciton involving an image-potential state of the vacuum are revealed through resonant Auger spectroscopy of the MgKL23L23 Auger transition. Our results demonstrate how to obtain new insights on empty states at interfaces of metal-supported ultrathin oxide films

Influence of elastic scattering on the measurement of core-level binding energy dispersion in X-ray photoemission spectroscopy

We explore the interplay between the elastic scattering of photoelectrons and the surface core level shifts with regard to the determination of core level binding energies in Au(111) and Cu3Au(100). We find that an artificial shift is created in the binding energies of the Au 4f core levels, that exhibits a dependence on the emission angle, as well as on the spectral intensity of the core level emission itself. Using a simple model, we are able to reproduce the angular dependence of the shift and relate it to the anisotropy in the electron emission from the bulk layers. Our results demonstrate that interpretation of variation of the binding energy of core-levels should be conducted with great care and must take into account the possible influence of artificial shifts induced by elastic scattering

Valence band structure of the Si(331)-(12 × 1) surface reconstruction

Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 × 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating semiconducting behavior. An occupied surface state, presumably containing several spectral components, is found centered at − 0.6 eV exhibiting a flat energy dispersion. These results are confirmed by scanning tunneling spectroscopy and are consistent with recent first-principles calculations for our structural model

Doping nature of native defects in 1T−TiSe₂

The transition-metal dichalcogenide 1T−TiSe₂is a quasi-two-dimensional layered material with a charge density wave (CDW) transition temperature of TCDW≈200  K. Self-doping effects for crystals grown at different temperatures introduce structural defects, modify the temperature-dependent resistivity, and strongly perturbate the CDW phase. Here, we study the structural and doping nature of such native defects combining scanning tunneling microscopy or spectroscopy and ab initio calculations. The dominant native single atom dopants we identify in our single crystals are intercalated Ti atoms, Se vacancies, and Se substitutions by residual iodine and oxygen

Self-ordered nanoporous lattice formed by chlorine atoms on Au(111)

A self-ordered nanoporous lattice formed by individual chlorine atoms on the Au(111) surface has been studied with low-temperature scanning tunneling microscopy, low-energy electron diffraction, and density functional theory calculations. We have found out that room-temperature adsorption of 0.09–0.30 monolayers of chlorine on Au(111) followed by cooling below 110 K results in the spontaneous formation of a nanoporous quasihexagonal structure with a periodicity of 25–38 Å depending on the initial chlorine coverage. The driving force of the superstructure formation is attributed to the substrate-mediated elastic interaction

Short-range phase coherence and origin of the 1T−TiSe21T-{\mathrm{TiSe}}_{2} charge density wave

The impact of variable Ti self-doping on the 1T−TiSe2 charge density wave (CDW) is studied by scanning tunneling microscopy. Supported by density functional theory, we show that agglomeration of intercalated-Ti atoms acts as preferential nucleation centers for the CDW that breaks up in phase-shifted CDW domains whose size directly depends on the intercalated-Ti concentration and which are separated by atomically sharp phase boundaries. The close relationship between the diminution of the CDW domain size and the disappearance of the anomalous peak in the temperature-dependent resistivity allows to draw a coherent picture of the 1T−TiSe2 CDW phase transition and its relation to excitons

Local resilience of the 1T\text{\ensuremath{-}}{\mathrm{TiSe}}_{2} charge density wave to Ti self-doping

In Ti-intercalated self-doped 1T−TiSe2 crystals, the charge density wave (CDW) superstructure induces two nonequivalent sites for Ti dopants. Recently, it has been shown that increasing Ti doping dramatically influences the CDW by breaking it into phase-shifted domains. Here, we report scanning tunneling microscopy and spectroscopy experiments that reveal a dopant-site dependence of the CDW gap. Supported by density functional theory, we demonstrate that the loss of the long-range phase coherence introduces an imbalance in the intercalated-Ti site distribution and restrains the CDW gap closure. This local resilient behavior of the 1T−TiSe2 CDW reveals an entangled mechanism between CDW, periodic lattice distortion, and induced nonequivalent defects