Université de Fribourg

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

Hildebrand, Baptiste ; Jaouen, Thomas ; Didiot, Clément ; Razzoli, Elia ; Monney, Gaël ; Mottas, Marie-Laure ; Vanini, Fabiano ; Barreteau, C. ; Ubaldini, A. ; Giannini, E. ; Berger, Helmuth ; Bowler, D. R. ; Aebi, Philipp

In: Physical Review B, 2017, vol. 95, no. 8, p. 081104

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...

Université de Fribourg

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

Hildebrand, Baptiste ; Jaouen, Thomas ; Didiot, Clément ; Razzoli, Elia ; Monney, Gaël ; Mottas, Marie-Laure ; Ubaldini, A. ; Berger, Helmuth ; Barreteau, C. ; Beck, Hans ; Bowler, D. R. ; Aebi, Philipp

In: Physical Review B, 2016, vol. 93, no. 12, p. 125140

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...

Université de Fribourg

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

Cherkez, V. V. ; Zheltov, V. V. ; Didiot, Clément ; Kierren, B. ; Fagot-Revurat, Y. ; Malterre, D. ; Andryushechkin, B. V. ; Zhidomirov, G. M. ; Eltsov, K. N.

In: Physical Review B, 2016, vol. 93, no. 4, p. 045432

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...

Université de Fribourg

Three-dimensional momentum-resolved electronic structure of $1T\text{-}{\mathrm{TiSe}}_{2}:$ A combined soft-x-ray photoemission and density functional theory study

Vydrova, Z. ; Schwier, Eike Fabian ; Monney, Gaël ; Jaouen, Thomas ; Razzoli, Elia ; Monney, Claude ; Hildebrand, Baptiste ; Didiot, Clément ; Berger, Helmuth ; Schmitt, T. ; Strocov, V. N. ; Vanini, Fabiano ; Aebi, Philipp

In: Physical Review B, 2015, vol. 91, no. 23, p. 235129

1T−TiSe2 is a quasi-two-dimensional transition metal dichalcogenide, which exhibits a charge density wave transition at a critical temperature of ∼200 K as well as low- temperature superconductivity induced by pressure or intercalation. The electronic energy dispersion measured by soft x-ray angle-resolved photoemission is not only momentum resolved parallel to the surface but also...

Université de Fribourg

Scanning tunneling microscopy of the charge density wave in $1T-{\mathrm{TiSe}}_{2}$ in the presence of single atom defects

Novello, Anna M. ; Hildebrand, Baptiste ; Scarfato, A. ; Didiot, Clément ; Monney, Gaël ; Ubaldini, A. ; Berger, Helmuth ; Bowler, D. R. ; Aebi, Philipp ; Renner, Christoph

In: Physical Review B, 2015, vol. 92, no. 8, p. 081101

We present a detailed low-temperature scanning tunneling microscopy (STM) study of the commensurate charge density wave (CDW) in $1T-{\mathrm{TiSe}}_{2}$ in the presence of single atom defects. We find no significant modification of the CDW lattice in single crystals with native defect concentrations where some bulk probes already measure substantial reductions in the CDW phase transition...

Université de Fribourg

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

Mariotti, Nicolas ; Didiot, Clément ; Schwier, Eike Fabian ; Monney, Claude ; Battaglia, Corsin ; Aebi, Philipp

In: Surface Science, 2015, vol. 639, p. 39-42

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,...

Université de Fribourg

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

Jaouen, Thomas ; Razzoli, Elia ; Didiot, Clément ; Monney, Gaël ; Hildebrand, Baptiste ; Vanini, Fabiano ; Muntwiler, M. ; Aebi, Philipp

In: Physical Review B, 2015, vol. 91, no. 16, p. 161410

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...

Université de Fribourg

Doping nature of native defects in 1T−TiSe₂

Hildebrand, Baptiste ; Didiot, Clément ; Novello, A. M. ; Monney, Gaël ; Scarfato, A. ; Ubaldini, A. ; Berger, Helmuth ; Bowler, D. R. ; Renner, Christoph ; Aebi, Philipp

In: Physical Review Letters, 2014, vol. 112, no. 19, p. 197001

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...

Université de Fribourg

Scanning tunneling microscopy at multiple voltage biases of stable “ring-like” Ag clusters on Si(111)–(7 × 7)

Mariotti, Nicolas ; Didiot, Clément ; Schwier, Eike Fabian ; Monney, Claude ; Perret-Aebi, Laure-Emmanuelle ; Battaglia, Corsin ; Garnier, M.G. ; Aebi, Philipp

In: Surface Science, 2012, vol. 606, no. 23-24, p. 1755-1759

Since more than twenty years it is known that deposition of Ag onto Si(111)–(7 × 7) leads under certain conditions to the formation of so-called “ring-like” clusters, that are particularly stable among small clusters. In order to resolve their still unknown atomic structure, we performed voltage dependent scanning tunneling microscopy (STM) measurements providing interesting...

Université de Fribourg

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

Schwier, Eike Fabian ; Monney, Claude ; Mariotti, Nicholas ; Vydrovà, Z. ; García-Fernández, Mirian ; Didiot, Clément ; Garnier, Michael G. ; Aebi, Philipp

In: The European Physical Journal B - Condensed Matter And Complex Systems, 2011, vol. 81, no. 4, p. 399-403

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...