Scanning Probe Microscopy and Spectroscopy
The laboratory runs four scanning probe microscopes (SPM) offering variable temperature (40 K to room temperature) and low temperature (5 K) conditions in ultrahigh vacuum (UHV). While the variable temperature scanning tunneling microscope (STM) mainly allows the study of temperature-dependent structural transitions, the low-temperature STMs offer the stability required for scanning tunneling spectroscopy (STS) based electronic characterization and manipulation of nanostructures. The most recent setup combining low temperature STM and non-contact atomic force microscopy (nc-AFM) combines state-of-the-art structural and electronic characterization at low temperature with ultimate spatial stability. An additional dedicated scanning probe microscope offers STM and AFM characterization under ambient conditions and in liquids. A dynamic nanostencil lithography system combining STM and AFM characterization with transport measurements serves as a rapid prototyping platform for the fabrication and characterization of nanoscale devices. For the spatially resolved characterization of planar field emission cathodes, we have developed a scanning anode field emission microscope (SAFEM) featuring different modes of operation that allow for a thorough characterization of all kinds of field emitters.
Photoelectron Spectroscopy and Diffraction
Our scanning probe instruments are supplemented by state-of-the-art photoelectron spectroscopy (PES) systems. These analytical tools provide complementary sample characterization capabilities regarding chemical, electronic and structural properties. Our two laboratory-based PES systems are both equipped with computerized full-hemisphere goniometer manipulators for angle-scanned PES. This allows to perform s-ray photoelectron spectroscopy (XPS) and diffraction (XPD) experiments using MgKα or AlKα excitation, as well as valence band spectroscopy (UPS, ARPES) using ultraviolet He I or He II radiation. For dedicated band structure measurements our newest system is equipped with a Scienta R3000 electron analyzer providing 2D detection (angle and energy) and sample cooling to 24 K. Furthermore, it is connected to a dedicated low-temperature (5 K) STM/nc-AFM instrument. As a founding consortium member, we have privileged access to the PEARL endstation of the Swiss Light Source to perform photon-energy and angle-scanned high-resolution XPS/XPD/ARPES measurements.
In addition to our analytical UHV SPM and PES systems, we dispose of a variety of dedicated sample growth and preparation tools. For the efficient on-surface synthesis of nanostructures we have developed a fully automated growth chamber, the so-called “GNR reactor”. This system automatizes substrate surface preparation, molecular precursor evaporation (up to 6 different molecules) and temperature-controlled polymerization and cyclodehydrogenation. The GNR reactor can reach a throughput of 12 samples per day. For the CVD growth of carbon nanomaterials we use a commercial 2” Black Magic system from AIXTRON with Graphene and Carbon Nanotube growth kits. With the corresponding growth protocols this system can produce dense forests of single-walled CNTs or sparse vertically aligned CNTs. For the surface modification and deposition of technologically relevant thin films we use a home-built plasma chamber featuring a HV chamber coupled to a 2.45 GHz microwave generator working under electron cyclotron resonance condition. This allows to maintain very low density (10-5 mbar) plasmas, which are very well suited for the plasma-enhanced CVD of organic thin films.
For preparatory work and ex-vacuum investigations, we have a dedicated laboratory space equipped for experiments in liquids and electrolytes, but also for the preparation of STM-tips and the determination of molecule sublimation temperatures and deposition rates. Besides two chemical fume hoods our chemistry lab houses several other pieces of equipment. The Nanoscope III Multimode from Veeco is a multi-purpose scanning probe microscope for STM and AFM in air and in electrolytes under electrochemical control, with the possibility of applying an inert gas atmosphere. For the preparation of SPM tips, the lab comprises a setup for the electrochemical etching of PtIr-tips in a salt melt and of W-tips in aqueous electrolyte. It also offers the possibility to insulate tips with Apiezon wax for electrochemical measurements. A µAutolabIII Potentiostat/Galvanostat is used for electrochemical characterisation. Water with a resistivity >18.2 MOhm cm is obtained from an ELGA Purelab Ultra Ionic system. To determine sublimation temperature and deposition rate of molecules prior to UHV experiments, the lab hosts a fully automatized high-vacuum system equipped with calibrated evaporation source and quartz crystal microbalance.
Hypatia computer cluster
Hypatia is a Linux-based computer cluster reaching 15 Teraflops of peak performance, with advanced interconnection protocols, large memory and CPU performance, disposes of a fast and reliable storage system of presently 90 TB, and is part of the swiss high performance computing strategy. Medium-sized applications, that cannot be run on desktop computers but do not make efficient use of the supercomputers of the swiss center for scientific computing (CSCS) in Lugano, are expected to find powerful and reliable hardware and software resources in commodity clusters built within the single research institutions. Hypatia runs a wide range of calculations: "parameter space spanning" jobs like environmental models or flight traffic noise simulation, which are typically performed by numerous single-processor calculation runs, small multi-physics parallel jobs for the analysis of materials, but also efficient parallel multiprocessor jobs for complex atmospheric models or high-level ab initio calculations applied to nanoscience. Examples of the latter are studies conducted in our laboratory on the topics presented in these web pages. With its easy accessibility, our local cluster enables for example a rapid property screening of putative nanosystems that could be realized experimentally.