Université de Fribourg

Carbon‐assisted stable silver nanostructures

Abdollahi, S. Narjes ; Ochoa Martínez, Efraín ; Kilchoer, Cédric ; Kremer, Geoffroy ; Jaouen, Thomas ; Aebi, Philipp ; Hellmann, Tim ; Mayer, Thomas ; Gu, Yibei ; Wiesner, Ulrich B. ; Steiner, Ullrich ; Wilts, Bodo D. ; Gunkel, Ilja

In: Advanced Materials Interfaces, 2020, vol. 7, no. 23, p. 2001227

Nanostructured silver stands out among other plasmonic materials because its optical losses are the lowest of all metals. However, nanostructured silver rapidly degrades under ambient conditions, preventing its direct use in most plasmonic applications. Here, a facile and robust method for the preparation of highly stable nanostructured silver morphologies is introduced. 3D nanostructured...

Université de Fribourg

Structure and stability of the Si(331)-(12×1) surface reconstruction investigated with first-principles density functional theory

Battaglia, Corsin ; Onida, Giovanni ; Gaál-Nagy, Katalin ; Aebi, Philipp

In: Physical Review B: condensed matter and materials physics, 2009, vol. 80, no. 21, p. 214102

We recently proposed a structural model for the Si(331)-(12×1) surface reconstruction containing silicon pentamers and adatoms as elementary structural building blocks. Using first-principles density functional theory we here investigate the stability of a variety of adatom configurations and determine the lowest-energy configuration. We also present a detailed comparison of the energetics...

Université de Fribourg

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

Battaglia, Corsin ; Schwier, Eike Fabian ; Monney, Claude ; Didiot, Clément ; Mariotti, Nicolas ; Gaál-Nagy, Katalin ; Onida, Giovanni ; Garnier, Michael Gunnar ; Aebi, Philipp

In: Journal of Physics: Condensed Matter, 2011, vol. 23, no. 13, p. 135003

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...

Université de Fribourg

Ab initio many-body effects in TiSe₂: A possible excitonic insulator scenario from GW band-shape renormalization

Cazzaniga, M. ; Cercellier, H. ; Holzmann, M. ; Monney, Claude ; Aebi, Philipp ; Onida, Giovanni ; Olevano, V.

In: Physical Review B - Condensed matter and materials physics, 2012, vol. 85, no. 19, p. 195111

We present both theoretical ab-initio results within the Hedin's GW approximation and experimental angle-resolved photoemission and scanning tunneling spectroscopy measurements on TiSe₂. With respect to the density-functional Kohn-Sham metallic picture, the many-body GW self-energy leads to a ≈0.2-eV band-gap insulator consistent with our STS spectra at 5 K. The highest valence and the lowest...

Université de Fribourg

On the electronic impact of abnormal C4-bonding in N-heterocyclic carbene complexes

Heckenroth, Marion ; Neels, Antonia ; Garnier, Michael G. ; Aebi, Philipp ; Ehlers, Andreas W. ; Albrecht, Martin

In: Chemistry - A European Journal, 2009///doi: 10.1002/chem.200900249

Sterically similar palladium dicarbene complexes have been synthesized that comprise permethylated dicarbene ligands which bind the metal center either in a normal coordination mode via C2 or abnormally via C4. Due to the strong structural analogy of the complexes, differences in reactivity patterns may be attributed to the distinct electronic impact of normal versus abnormal carbene bonding,...

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

Local real-space view of the achiral $1T\text{\ensuremath{-}}{\mathrm{TiSe}}_{2}$ $2\times2\times2$ charge density wave

Hildebrand, Baptiste ; Jaouen, Thomas ; Mottas, Marie-Laure ; Monney, Gaël ; Barreteau, C. ; Giannini, E. ; Bowler, D. R. ; Aebi, Philipp

In: Physical Review Letters, 2018, vol. 120, no. 13, p. 136404

The transition metal dichalcogenide 1T−TiSe2-two-dimensional layered material undergoing a commensurate 2×2×2 charge density wave (CDW) transition with a weak periodic lattice distortion (PLD) below ≈200 K. Scanning tunneling microscopy (STM) combined with intentionally introduced interstitial Ti atoms allows us to go beyond the usual spatial resolution of STM and to intimately probe...

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

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

Evolution of the charge density wave superstructure in ${\mathrm{ZrTe}}_{3}$ under pressure

Hoesch, Moritz ; Garbarino, Gaston ; Battaglia, Corsin ; Aebi, Philipp ; Berger, Helmuth

In: Physical Review B, 2016, vol. 93, no. 12, p. 125102

The material ZrTe3 is a well-known example of an incommensurate periodic lattice distortion (PLD) at low temperatures due to a charge density wave (CDW). Previous studies have found a sharp boundary as a function of pressure between CDW below 5 GPa and bulk superconductivity above this value. We present a study of low-temperature-high-pressure single crystal x-ray diffraction along with ab initio...