Presentation materials
Many important chemical and biological processes occur at the interface between a solid and a liquid. Despite its importance, it is very difficult to collect meaningful signals from this buried interface. We recently built a new instrument at the Swiss Light Source that combines ambient-pressure X-ray photoelectron spectroscopy with in-situ electrochemistry. With this new setup, we can...
Cuprous oxide is a promising material for light absorption and charge separation in photoelectrochemical cells for solar water splitting. We have investigated the electron dynamics on the (111) surface of Cu2O. Depending on the defect concentration, this surface shows two different reconstructions. For the (1x1) structure a fast relaxation of a higher conduction band into the conduction band...
Photocatalytic water splitting allows storing solar energy as chemical energy. For large scale application in photoelectrochemical (PEC) cells, electrode materials need to be efficient and stable. In this work we investigate single-crystalline antimony selenide (Sb2Se3), a p-type semiconductor with excellent light absorbing properties and promising stability towards photocorrosion in aqueous...
The hexagonal boron nitride (h-BN) nanomesh that forms on Rh(111) has a corrugated honeycomb structure with 3.2 nm periodicity, which consists of “pore” and “wire” regions [1, 2]. In the present study, we demonstrate that 2 nm voids can be fabricated at the pore sites in the h-BN monolayer with unique two-step process in vacuum [3, 4], and can be further delaminated from a Rh substrate with...
The growth of hexagonal Boron Nitride (h-BN) monolayers on Pt(110) was investigated by STM, LEED and DFT calculations. Borazine exposure at T < 1100 K yields an h-BN film with defects and domain boundaries on a rough Pt surface as previously reported by Achilli et al. [Nanotechnology 29 (2018) 485201]. Deposition at T > 1100 K results in a perfect single-domain h-BN layer on a flat Pt(110)...
On- surface synthesis enables fabrication of graphene nanoribbons (GNRs) with atomically precise edges and ribbon width which allows tuning their electronic bandgap. This feature makes GNRs interesting candidates for application in room temperature switching devices like field effect transistors (FETs). However, integrating GNRs as the active material in FETs poses great challenges concerning...
PdGa(111) surface is of remarkable interest because of its enantio- and region-selective properties. In this work we present experimental and theoretical results concerning the PdGa-catalysed Huisgen cycloaddition (in the Figure, experimental STM images of reactants and products on PdGa(111)), with particular focus on the DFT modelling of the compounds. The calculations were performed treating...
Investigating charged molecules on insulating films is experimentally challenging. Atomic force microscopy, with single-electron sensitivity and capable of operating on insulating substrates, is a promising technique for such studies. Here we demonstrate multiple charge-state stabilization of molecules, induce intermolecular single-electron transfer and show that the charge state of a complex...
Porphyrin-substrate hybrid systems are the building blocks in a series of materials, such as the organic light-emitting diodes, chemical sensors and dye-sensitized solar cells. Understanding and correctly describing the way molecules interact with the substrate upon adsorption hold the key to the prediction and improvement of the present-day devices.
Recently, distinct features were...
Metal-organic interfaces are systems of great interest for both fundamental concepts in electronic structure theory and numerous promising technological applications. Recently, it was demonstrated that an insulating interlayer of MgO on an Ag(100) surface does not simply decouple the metal- and organic-layer but actively promotes charge transfer. While this has been shown for the case of...
Metal complexes containing gold in the formal oxidation state +I exhibit a very strong metallophilic interaction, which is often decisive for their arrangement in the solid state. To study this attractive interaction on surfaces, we investigated films with a thickness of just a few layers of 2-naphthyl-isonitrile-gold(I)-chloride on Au(111) and Au(110) surfaces. The physical vapor deposition...
On-surface synthesis allows to design carbon nanostructures such as graphene nanoribbons with atomic precision. However, the variety of conceivable structures critically depends on the number of available reaction concepts. Here, we present a new surface-assisted reaction allowing for the controlled fusion of two alkyl groups to form a phenyl ring. Scanning tunneling and non-contact atomic...
Acenes are a class of polycyclic aromatic hydrocarbons that exhibit impressive semiconductor and open-shell properties. These unique properties can be tailored to potential applications by altering the conjugated π-system with chemical doping. The synthesis of large acenes via traditional solution-chemistry route is hindered by their poor solubility and high reactivity. In this work, we...
Differential very low energy electron diffraction spectra have been measured on a Highly Oriented Pyrolitic Graphite (HOPG) surface in the range of landing energies from 0-1600eV. The reflectivity in the band gap, in between the interlayer resonances, differs from unity, implying that the vacuum wave function can penetrate the surface, but it is strongly damped via excitation of
This study aims at direct imaging of contact resistance in MoS2-based thin film transistors (TFTs). Exfoliated single-crystal flakes of MoS2 have been used in a bottom-contact TFT configuration. Pyrimidine-containing self-assembled monolayers (SAMs) were employed to tune the work function of gold electrodes. Kelvin probe force microscopy measurements were carried out...
InteractiveXRDFit is a Matlab program that calculates the X-ray diffracted intensity for heterostructures. The user can choose the substrate and the different materials composing an heterostructure among a long list of compounds, choose between (001) or (111) substrate orientation, and play with the different structural parameters (unit-cell size and number of layers). It is possible to build...
