Ai Leen Koh

Applications of environmental (scanning) transmission electron microscopy to study oxidation and hydrogenation phenomena in nanomaterials

Stanford Nanocharacterization Laboratory, Stanford University

Environmental (scanning) transmission electron microscopy (E(S)TEM) is a method to investigate the behavior of nanomaterials in gases at atomic resolution.  In the first part of this talk, I will describe the basic setup of the E(S)TEM.  Then, I will discuss its applications relating to oxidation of carbon nanotubes (CNTs) and hydrogenation of individual palladium nanocrystals.

Since their discovery in 1991 carbon nanotubes (CNTs) [1] have found an increasing number of applications, most notably as field emission electron sources in X-ray tubes for medical applications [2, 3].  In a laboratory setting, field emission measurements of CNTs are usually carried out in an ultrahigh-vacuum system with base pressure of ~ 10-7 mbar or better.  Under less stringent vacuum conditions, CNTs are found to exhibit lower emission currents and reduced lifetimes [4, 5].  Shortly after the discovery of CNTs, several groups attempted to utilize the oxidation process to manipulate their structures, for instance by opening up their terminating cap or by thinning the tubes [6, 7].  In the literature, these oxidation steps were usually performed in an external laboratory setting, and the state of the oxidized samples was surveyed a posteriori with a transmission electron microscope (TEM).  However, because of their nanoscale, no direct study has been performed on the underlying mechanism of their oxidation.  Recently, we reported the direct study on the structural changes in CNTs as we heated and oxidized them in-situ using an aberration-corrected E(S)TEM [8].  We also established a protocol whereby heating and oxidation were performed without an imaging beam, and the changes on identifiable nanotubes were documented after purging the gas from the chamber, to ensure that they were due to the effect of gaseous oxygen molecules on the nanotubes, rather than the ionized gas species [8].

We have also utilized electron energy-loss (EEL) spectroscopy in the E(S)TEM to probe hydrogen absorption in individual Pd nanocrystals, by measuring the shift in their bulk plasmon resonance modes, as Pd transforms into PdHx during hydrogen absorption. Using this approach, we constructed pressure – energy-loss isotherms of individual Pd nanocrystals and obtained insights into the hydrogen intercalation in nanostructured metals [9]. The examples described highlight the strengths of the E(S)TEM as a tool which enables us to understand the behavior of nanomaterials in reactive gas environments.

References:
[1] S Iijima, Nature 354 (1991), pp. 56-58.
[2] G. Cao et al., Med. Phys. 37 (2010), pp. 5306–5312.
[3] X. Qian et al., Med. Phys. 39 (2012), pp. 2090–2099.
[4] K. A. Dean and B. R. Chalamala, Appl. Phys. Lett. 75 (1999), pp. 3017–3019.
[5] J.-M. Bonard, et al., Ultramicroscopy 73 (1998), pp. 7–15.
[6] P. M. Ajayan et al., Nature 362 (1993), pp. 522–525.
[7] S. C. Tsang, P. J. F. Harris and M. L. H. Green, Nature 362 (1993), pp. 520–522.
[8] A.L. Koh, et al., ACS Nano 7, 2013, 2566-2572.
[9] A. Baldi et al., under review (2014).

Alexander Vaskevich

Plasmonic sensors: Materials, Methods, Mistakes

Weizmann Institute of Science, Israel

Application of surface plasmon resonance (SPR) spectroscopy for the development of sensing and biosensing technologies represents an extremely diverse area of research combining together applied physics and surface chemistry. Instruments based on propagating SPR spectroscopy are commercially available, while numerous prototype systems based on localized SPR (LSPR) spectroscopy are not commercialized yet because of general problems in design and signal optimization of LSPR biosensors. Most of these problems will be discussed in these lectures.
We will discuss:

• Different approaches to fabrication of LSPR transducers and morphological stability of plasmonic nanostructures;
• Experimental results and numerical modelling of sensitivity of LSPR transducers. Particular attention will be paid to evaluation of realistic detection limits for biological applications of refractometric plasmonic sensors;
• Preparation and optimization of molecular recognition interfaces for typical biosensing applications: immunosensing, sugar-protein interactions, specific binding of DNA and RNA.

We will evaluate possible applications of LSPR spectroscopy where this method has an advantage over other techniques.

Christiane Becker

1) Crystalline Si thin films for photovoltaics
2) Nanophotonic light trapping (including nanoimprint lithography)

Helmholtz Zentrum Berlin

Lecture I: Crystalline silicon thin-film solar cells
Photovoltaics is a simple and elegant method for the direct conversion of the sun's energy into electricity. Today it is a rapidly growing and increasingly important renewable alternative to conventional fossil fuel electricity generation. The photovoltaic sector is currently dominated by wafer-based crystalline silicon solar cells with a market share of almost 90%. However, thin-film solar cell technologies allow for significantly reduced material costs and large-area manufacturing processes and are therefore a promising alternative. The lecture summarizes recent advances and challenges of crystalline silicon thin-film solar cell technology and is organized as follows:

1. Short introduction photovoltaics
2. Crystalline silicon as photovoltaic material
3. Fabrication methods for crystalline silicon thin films
4. Defects and microstructure of crystalline silicon films
5. Crystalline silicon thin-film solar cells

Lecture II: Nanophotonic light trapping & Nanoimprint-lithography
The second lecture addresses light trapping as important issue for thin-film solar cells, particularly when a lowly absorbing material such as crystalline silicon is used.  Recent progress in nanophotonic light management strategies enables the reduction of material to less than one hundredth compared to silicon wafer based devices. The lectures summarizes the physical limits of light trapping in a thin absorbing film, introduces nanoimprint-lithography as promising technology enabling the nanopatterning of large-area devices on industrial scale and presents first results on nanophotonic light trapping in crystalline silicon thin-film solar cells. The presentation is organized as follows:

• Physical limits of light trapping in thin films
• Nanoimprint-lithography
• Light management concepts in silicon thin film solar cells
• Challenge: Trade-off optical versus electronic device performance

Gerhard Meyer

Atomically resolved scanning probe microscopy

Physics of Nanoscale Systems group at the IBM Research - Zurich Laboratory

High resolution structural information and manipulation on the atomic scale [1,2] can be obtained by Atomic Force Microscopy (AFM) [3]. In the case of molecules this leads to the direct imaging of the molecular geometry [4]. The key to such high lateral resolution on molecules are specific AFM tip terminations (for example CO transferred to the tip by atomic manipulation) to tune the interaction of the tip with the adsorbed molecule. The high resolution can be used for example to determine the bond order in planar aromatic molecules, the adsorption height and tilt of the molecule and the chemical structure of unkown molecular compounds. The combination of STM and AFM is a unique tool to study the operation of molecular switches resolving the details of the bond formation/breaking processes and conformational changes on the atomic scale. The reversible bond formation between a gold adatom and a PTCDA molecule constitutes a reliable molecular switch [5]. As with the STM the charge state information can be directly obtained with the AFM [6]. Finally it will be shown that Kelvin probe force microscopy (KPFM) can map the local contact potential difference with submolecular resolution reflecting the intramolecular charge distribution [7].

[1] Y. Sugimoto et al., Nat. Mater. 2005, 4, 156
[2] M. Ternes, C. P. Lutz, C. F. Hirjibehedin, F. J. Giessibl, A. J. Heinrich, Science 2008, 319, 1066
[3] F. J. Giessibl, Rev. Mod. Phys.2003, 75, 949
[4] L. Gross, F. Mohn, N. Moll, P. Liljeroth, G. Meyer,  Science 2009, 325, 1110
[5] F. Mohn, J. Repp, L. Gross, G. Meyer, M. S. Dyer & M. Persson, Phys. Rev. Lett. 2010, 105, 266102
[6] L. Gross, F. Mohn, P. Liljeroth, J. Repp, F. J. Giessibl, G. Meyer, Science 2009, 324, 1428
[7] F. Mohn, L. Gross, N. Moll, G. Meyer, Nature Nanotechnology 2012, 7, 227

Gregory Weiss

Single-Molecule Enzymology with Nanometer-Scale Electronics

Department of Chemistry at University of California Irvine

Interrogating patient samples for disease diagnosis could be more rapid, less expensive and more routine, if the molecular recognition necessary for disease marker identification could be coupled directly to an electronic signal.  Towards this goal, the Weiss laboratory collaborates with electrochemist Prof. Reg Penner to directly wire viruses into electronic circuits.  Using phage display and synthetic chemistry to engineer the viral surfaces provides an inexpensive and very effective platform for biomarker recognition.  A composite surface of engineered viruses and the conducting polymer, PEDOT, could be electrodeposited onto electrodes for fabrication of sensitive area detectors for direct, cancer biomarker readout in synthetic urine.

Lecture 2. Single-Molecule Enzymology with Nanometer-Scale Electronics
The Weiss laboratory develops new tools using chemistry to understand biology at the level of atoms and bonds.  The lab directly wires viruses and individual proteins into electronic circuits, and electronically “listens” to their interactions with binding partners and enzyme substrates.  For example, with collaborator, Phil Collins, we have spot-welded individual proteins into nanometer-scale circuits.  Using the electronic signature of the resultant nanocircuit, the single protein can be examined in real-time during protein unfolding, folding, binding, and enzymatic catalysis.  The approach has been used to dissect lysozyme, DNA polymerase, and protein kinase A.  For each enzyme, we can obtain a large number of independent time-scales of the motion governing the enzyme dynamics (e.g., seven for lysozyme) under different conditions (e.g., in the presence of different nucleotides and DNA templates for DNA polymerase).  Such information adds to and extends our mechanistic understanding of each enzyme’s catalytic activity.
 
References
Sims, P.C., Moody, I.S., Choi, Y., Dong, C., Iftikhar, M., Corso, B.L., Gul, O.T., Collins, P.G.*, Weiss, G.A.* (2013). Electronic measurements of single-molecule catalysis by cAMP-dependent protein kinase A. J. Amer. Chem. Soc. 135: 7861-7868.
Olsen, J., Choi, Y., Sims, P.C., Gul, O.T., Corso, B.L., Dong, C. Brown, W.A., Collins, P.G.*, Weiss, G.A.* (2013). Electronic measurements of single-molecule processing by DNA polymerase I (Klenow Fragment). J. Amer. Chem. Soc. 135: 7855-7860. Joint first two authors.
Mohan, K., Donavan, K.C., Arter, J.A., Penner, R.M.*, Weiss, G.A.* (2013). Sub-nanomolar detection of prostate specific membrane antigen in synthetic urine by synergistic, dual ligand phage. J. Amer. Chem. Soc. 135: 7761-7767.
Choi, Y., Moody, I.S., Sims, P.C., Hunt, S.R., Corso, B.L., Perez, I., Weiss, G.A.*, Collins, P.G.* (2012). Single molecule lysozyme dynamics monitored by an electronic circuit. Science. 335: 319-324.

Volker Schmidt

Semiconductor nanowires for ultimate and post-CMOS applications

Nanoscale Electronics group at IBM Research – Zurich

Tunnel field-effect transistors as energy-efficient electronic switches
http://www.nature.com/nature/journal/v479/n7373/full/nature10679.html

Vertical III–V Nanowire Device Integration on Si(100)
http://pubs.acs.org/doi/abs/10.1021/nl404743j

Isodiana Crupi

Flexible thin film photovoltaics and plasmonics

CNR-IMM, Catania, Sicily, Italy

Jakub Dostálek

Plasmonics for biosensing of chemical and biological compounds

Austrian Institute of Technology GmbH

Plasmonics represents a research area that investigates confinement of light by metallic nanostructures supporting surface plasmons – coupled oscillations of electromagnetic field and electron charge density. The resonant excitation of surface plasmons allows for sensitive probing of molecular binding events occurring on metallic surfaces and it paved ways to the development of numerous important tools in areas of life sciences and medical diagnostics. These include label-free surface plasmon resonance (SPR) biosensors, surface-enhanced Raman spectroscopy (SERS), surface-enhanced infrared spectroscopy (SEIRA), and surface plasmon-enhanced fluorescence spectroscopy (PEF). The course will provide an introduction to fundamentals in surface plasmon resonance optics and to various implementations of plasmonics for detection of molecular analytes and their interaction analysis:

• Introduction to optical phenomena exploited in optical biosensors: ray, wave optics, electromagnetic optics, total internal reflection, guided wave optics, surface plasmon resonance, fluorescence, and Raman scattering.
• Technologies for preparation of optical micro- and nano-structures: thin film deposition, top down and bottom up fabrications, photo- electron beam lithography, colloidal lithography, nano-imprint lithography. 
• Optical spectroscopy: fluorescence, Raman scattering, and IR absorption detection. Sensor signal enhancement strategies – surface-enhanced Raman spectroscopy (SERS), surface-enhanced fluorescence (SEF).
• Label-free plasmonic biosensors. Localized and propagating surface plasmon resonance (SPR).
• Heterogeneous assay-based biosensors. Reaction kinetics and evaluation of affinity binding constants for molecular interaction analysis (BIA).

Jiří Orava

Amorphous chalcogenides and marginal glass-forming melts
Fast and slow kinetics in amorphous chalcogenides for non-volatile solid-state memories

University of Cambridge & Tohoku University, Advanced Institute for Materials Research

Klaus Ensslin

Nanoelectronic devices

Department of Physics, ETH Zurich

Kris Poduska

Tracking the life cycle of a material through its structure, bridging the nanoscale with the macroscale

Memorial University of New Foundland, Canada

One of the fundamental themes in materials science research is understanding how the way in which a material is synthesized and processed can be used to tune its physical properties (optical, electronic, magnetic, mechanical, and others). Equally important is understanding how the environment in which a material is used can change its performance over time. In my first lecture, I will give a general overview of the synthesis-structure-properties approach to the development of materials for technological applications. I will also explain how environmental factors, such as the presence of water and the application of voltages, can change the structure and properties of a material during its use. In my second lecture, I will give two applied examples from my own research program: (1) synthesis and ambient degradation of transparent semiconductors, (2) synthesis and time-dependent changes in archaeological materials. Taken together, the two lectures are designed to demonstrate that a detailed understanding of a material's structure can provide clues about how it was formed, and can also provide hints about how it might change during future use.

Pascal Ruffieux

Graphene and carbon nanomaterials

Nanotech @ surfaces, EMPA Dübendorf

Graphene, a single atomic layer of sp2-bonded carbon, holds significant potential as a new material for electronic applications due to a number of intriguing properties such as high charge carrier mobility, ballistic transport, wavelength-independent absorption of visible light as well as outstanding mechanical properties and chemical inertness. Here, an overview of graphene’s most important properties and a review of advances in graphene synthesis and transfer technology will be presented. Special attention will be given to graphene-related nanostructures such as carbon nanotubes and graphene nanoribbons, which allow for the controlled manipulation of graphene’s electronic and optical properties. To this end, bottom-up strategies allowing for the deterministic fabrication of atomically précised 1D and 2D graphene nanostructures will be discussed. A detailed review of recent studies of their electronic and optical properties will be given.

Patrik Schmutz

1) Corrosion issues and electrochemical methodologies
2) Case study - Biodegradable Mg implants characterization

Joining Technologies and Corrosion, EMPA Dübendorf

     Newly developed metallic materials and engineered system often generate laterally heterogeneous (down to the nanoscale) reactive surfaces. Their interaction with environment can further dramatically affect surface (and later bulk) functionalities as well as results in component failure especially critical for medical implants. A precise assessment of environmental (atmospheric, aqueous) degradation can be obtained by electrochemical methods that are very sensitive in detecting early stages of surface modifications.   
     During the first lecture, new electrochemical methodologies development specific for characterization of corrosion issues at the local scale will be presented. First, micro- and nanocapillary electrochemical characterization of surfaces will be introduced. By restricting the electrolyte contact to the end of a very small pulled capillary (diameter down to 20nm), it is possible to investigate local electrochemical reactivity of heterogeneous materials (phases, inclusions, impurities) without exposing large areas to electrolyte (like in liquid AFM/STM). These investigations are then often combined with Environmental Atomic Force Microscopy (AFM) coupled to Scanning Kelvin Probe Force Microscopy (SKPFM) surface potential characterization. Molecular adsorption, electrochemical double layer building up and surface modification induced by atmospheric interactions can be investigated online from high vacuum up to 95% RH (from room to elevated temperature) or in presence of aggressive ions.
     In the second lecture, application of electrochemical impedance spectroscopy (EIS) and analytical techniques for Biodegradable Mg alloy implants characterization will be discussed. Magnesium and its alloys have a poor corrosion resistance, except in the alkaline domain, where passivity can be established. Recently, a positive use of the high corrosion susceptibility of these alloys (especially the Mg-Ca-Zn system) attracted interest of the medical community as biodegradable pins, plates/meshes and stents. The problem faced concerning implant lifetime prediction in the pH domain of physiological media is that we are not in presence of direct active dissolution. The formation mechanisms of “partially protecting” Mg-hydroxide corrosion products on multiphase surfaces is quite complex. Therefore, In-vitro electrochemical experiments in simulated body fluids (SBF) are still needed in order to further investigate fundamental issues about local reactivity (microstructure, role of intermetallics) of Mg alloys. The Mg degradation is also an ideal case study to present the electrochemical impedance spectroscopy technique. The frequency dependant information of the EIS technique is very rich and allows identifying a whole range of processes from multiple, locally separated, charge transfer on the surface to the assessment of dielectric constant of ultrathin protecting oxides. A more advanced data analysis can further allow evidencing diffusion and adsorption processes.
    

Suneel Kodambaka

Role of Interface Structure on Electronic Properties of Heterostructured 2D Layers

University of California, Los Angeles

The newly emerging class of two-dimensional (2D) materials exhibit a wide range of properties (e.g., graphene is metallic, h-BN is insulating, and MoS2 is semiconducting) and are attractive for opto- and nano- electronic applications. Recent efforts have focused on vertical integration of 2D layers of dissimilar materials (e.g., graphene/h-BN and graphene/MoS2). In these heterostructures, due to relatively weak vdW interactions, orientational registry between the layers is not expected and is often difficult to control. This talk will focus on the effect of interlayer orientation on the electronic structure of the resulting heterostructures. Using a combination of in situ low-energy electron microscopy (LEEM) and density functional theory (DFT) calculations, we investigated the electronic properties of monolayer graphene on metal (Pd) and graphene on graphene. From the LEEM images we determine the graphene growth kinetics and measure variations in surface work function with changes in the graphene layer orientation. More recently, we extended our DFT calculations to study the effect of monolayer graphene on the electronic properties of h-BN and MoS2 layers. We found that hBN can chemisorb or physisorb on Ni(111), with metallic or insulating properties, respectively and these properties are not altered when graphene is placed atop hBN. For graphene on MoS2, we found that rotating graphene layer by 30o with respect to MoS2 changes the MoS2 band gap from 1.68 eV direct to 1.56 eV indirect. We attribute the observed orientation-dependent bandgap to the variation in the S-S interplanar distance with the MoS2-graphene interlayer orientation. Our studies provides important insights into the role of interface structure on the electronic properties of 2D layered materials.

Ulrike Diebold

Oxide Surfaces at the Atomic Scale

Surface Physics, Institute of Applied Physics, TU Vienna

Surface science studies of metal oxides have experienced a rapid growth.  The reasons for this increasing interest are quite clear:  after all, most metals are oxidized under ambient conditions, so in many instances it is the oxidized surface that deserves our attention.  In addition, bulk metal oxides exhibit an extremely wide variability in their physical and chemical properties.  These are exploited in established and emerging technologies such as catalysis, gas sensing, and energy conversion schemes, where surfaces and interfaces play a central role in device functioning.  Hence a more complete understanding of metal oxide surfaces is desirable from both a fundamental and applied points of view. 
By using Scanning Tunneling Microscopy measurements, in combination with Density Functional Theory calculations and area-averaging spectroscopic techniques, great strides have been made in understanding the atomic-scale properties of the surfaces of several oxide materials.  In the talk I will give examples drawn from recent studies [1-4] of bulk single crystals including TiO2 and Fe3O4.

References
[1] Philipp Scheiber et al. Physical Review Letters, 105 (2010) 216101; ibid. 109 (2012) 136103
[2] Martin Setvin et al., Science, 341 (2013) 988
[3] ZbyněkNovotný et al., Physical Review Letters, 108 (2012) 216103
[4] Gareth S. Parkinson, et al., Nature Materials, 12 (2013) 724 - 728

Wolf-Dieter Schneider

Spectroscopic manifestations of low-dimensional physics: A local view

Institute of Condensed Matter Physic EPFL

Lecture I

A detailed knowledge of the electron transport properties and the electronic structure of metallic nanostructures on dielectric supports is not only important for the development of a future nanoscale electronics but also for the selection and the improvement of nanoscale catalysts in heterogeneous catalysis. However, the accurate characterization and understanding of such systems at the nanoscale is an experimentally challenging task. In the past, we investigated with low-temperature scanning probe techniques [1] nanoscale Pb-islands on different supports and elucidated their size-dependent supraconducting properties [2], electron confinement [3], and dynamical Coulomb blockade phenomena [4]. Here, we study the transport properties and the electronic structure of individual nanosized double-barrier tunnel junctions consisting of a tip, flat metallic Pb islands, and a supporting dielectric ultrathin NaCl film on Ag(111). The observed differential conductance spectra display the presence of Coulomb blockade phenomena [5] characteristic for single-electron tunneling processes, which are well described within the semi-classical orthodox theory. Under specific tunneling conditions in the Coulomb staircase regime, very striking concentric lines which follow the island contours, are visible in topographic images as well as in dI/dV maps. These Coulomb charge rings reflect the influence of the tip-island junction on the fractional residual charge Q0 on the nanoisland [5].
[1] R. Gaisch et al., Ultramicroscopy 42‑44, 1621 (1992).
[2] C. Brun et al, Phys. Rev.  Lett. 102, 207002 (2009).
[3] I.-P. Hon at al Phys. Rev. B 80, 081409(R) (2009).
[4] C. Brun et al., Phys. Rev. Lett. 108, 126802 (2012).
[5] I. P. Hong et al., Front. Physics 1, 13 (2013).

Lecture II

The interest in nanostructured materials, consisting of building blocks of a small number of atoms or molecules, arises from their promising new optic, catalytic, magnetic and electronic poperties, which are fundamentally different from their macroscopic bulk counterparts. Here we present selected examples of our research, which elucidate local aspects of physics in low dimensions investigated by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS): electronic properties (electron confinement, supraconductivity, and electron transport) of ultrathin supported metal islands [1-6], self-assembly, melting, and electronic structure of two-dimensional adatom superlattices stabilized by long-range electronic interactions [7-11], two-dimensional supramolecular self-assembly, chirality, electronic structure, and local fluorescence and phosphorescence of small organic molecules [12-23],  enabling chemical recognition at the molecular scale.

[1] I.-P. Hong et al: Decay Mechanisms of Excited Electrons in Quantum Well States of Ultrathin Pb Islands Grown on Si(111): Scanning Tunneling Spectroscopy and Theory. Phys. Rev. B 80, 081409(R) (2009).
[2] X. Shao at al. Growth of two-dimensional Lithium islands on CaO(001) thin films. J. Phys. Chem. C 116, 17980 (2012).
[3] C. Stiehler et al: Electron quantization in arbitrarily shaped gold islands on MgO thin Films. Phys. Rev. B 88, 115415 (2013).
[4]  C. Brun at al.: Reduction of the superconducting gap in ultrathin Pb islands grown on Si(111). Phys. Rev. Lett. 102, 207002 (2009).
[5] C. Brun et al: Dynamical Coulomb blockade observed in nanosized electrical contacts. Phys. Rev. Lett. 108, 126802 (2012).
[6] I. P. Hong et al: Coulomb blockade phenomena observed in supported metallic nanoislands. Front. Physics 1,13 (2013).
[7] F. Silly et al.: Creation of an atomic superlattice by immersing metallic adatoms in a two-dimensional electron sea. Phys. Rev. Lett. 92, 016101 (2004).
[8] M. Ternes et al: Scanning tunneling spectroscopy of surface state electrons scattered by a slightly disorderd two-dimensional dilute “solid”: Ce on Ag(111). Phys. Rev. Lett. 93, 146805 (2004).
[9] F. Silly et al.:: Coverage dependent self-organization: From individual adatoms to adatom superlattices. New J. Phys. 6, 16 (2004).
[10] N. N. Negulyaev et al: Melting of  two-dimensional adatom superlattices stabilized by long-range  electronic interactions. Phys. Rev. Lett. 102, 246102 (2009).
[11] M. Ternes, M. Pivetta, F. Patthey, and W.-D. Schneider: Creation, electronic properties, disorder, and melting of two-dimensional surface-state-mediated adatom superlattices. Prog. Surf. Sci. 85, 1 – 27 (2010).
[12] M.-C. Blüm et al.: Conservation of chirality in a hierarchical supramolecular self-assembly of pentagonal symmetry. Angew. Chem. Int. Ed. 44 , 5334-5337 (2005).
[13] M.-C. Blüm et al: Probing and locally modifying the intrinsic electronic structure and the conformation of supported nonplanar molecules. Phys. Rev. B 73, 195409 (2006).
[14] M. Pivetta et al: Two-dimensional tiling by rubrene molecules self-assembled in supramolecular pentagons, hexagons, and heptagons on Au(111). Angew. Chem. Int. Ed. 47, 1076 (2008).
[15] M. Pivetta, et al: Three-dimensional chirality transfer in multilayer rubrene islands on Au(111). J. Chem. Phys. B 113, 4578 (2009).
[16] G. Tomba et al: Supramolecular self assembly driven by electrostatic repulsion: The 1D aggregation of rubrene pentagons on Au(111), ACS Nano 4, 7545–7551 (2010).
[17] M. Pivetta et al: Coverage-dependent self-assembly of rubrene molecules on noble metal surfaces observed by scanning tunneling microscopy. ChemPhysChem 11, 1558 (2010).
[18] R. Berndt et al.: Photon emission at molecular resolution induced by a tunneling microscope. Science 262, 1425 (1993).
[19] E. Cavar et al.: Fluorescence and phosphorescence from individual C60 molecules excited by local electron tunneling. Phys. Rev. Lett. 95, 196102 (2005).
[20] F. Rossel et al.: Plasmon enhanced luminescence from fullere molecules excited by local electron tunneling. Optics Express 17, 2714 (2009).
[21] F. Rossel et al: Luminescence experiments on supported molecules with the Scanning Tunneling Microscope. Surf. Sci. Rep. 65, 129 – 144 (2010).
[22] F. Rossel et al: Growth and characterization of fullerene nanocrystals on NaCl/Au(111). Phys. Rev. B 84, 075426 (2011).
[23] W.-D. Schneider: Scanning Tunneling Microscopy and Spectroscopy of Supported Nanostructures. Chimia 66, 16– 22 (2012). Special Volume “30 Years of Scanning Tunneling Microscopy”, Ed.: K.-H. Ernst.