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The supplementary material provides the description how to calculate the interference pattern, caused by the interaction with a line defect, like a step edge, for electronic states of a nearly free electron system embedded in a weak 1D potential.

The electronic state at the interface between the Ag(111) surface and NaCl island has been studied. Due to the lattice mismatch, islands of NaCl grow on Ag(111) with various moiré patterns which lead to a weak periodic one-dimensional (1D) potential for the electronic state. In contrast to the well-known situation for a purely 1D system, the ideal two-dimensional system should cause a modulation of the local electronic density for energies only below and not above the mini band gap corresponding to the periodic potential. However, the experimental observation by scanning tunneling microscopy and spectroscopy of states reveals such a modulation also in the forbidden range of energy. Since the particular system allows us to disentangle the effects of local scattering and those caused by the periodic potential, it could be revealed that the loss of coherence and the mechanism of the detection by the STM are responsible for the experimentally observed modulation, which should be suppressed in the case of an ideal system.

The dehydrogenation and dechlorination of FeOEP-Cl on Cu(111) has been studied in detail by scanning tunneling microscopy. Although, it is not possible to follow the reaction of an individual molecule, the complete pathway of the reaction with 22 inequivalent intermediate states and the rates of the involved processes are revealed. This is achieved by combining the analysis of a large data set showing thousands of molecules in the different stages of the reaction with numerical simulations.

We report on a reversible structural phase transition of a two-dimensional system that can be locally induced by an external electric field. Two different structural configurations may coexist within a CO monolayer on Cu(111). The balance between the two phases can be shifted by an external electric field, causing the domain boundaries to move, increasing the area of the favored phase controllable both in location and size. If the field is further enhanced new domains nucleate. The arrangement of the CO molecules on the Cu surface is observed in real time and real space with atomic resolution while the electric field driving the phase transition is easily varied over a broad range. Together with the well-known molecular manipulation of CO adlayers, our findings open exciting prospects for combining spontaneous long-range order with man-made CO structures such as >molecule cascades> or >molecular graphene>. Our new manipulation mode permits us to bridge the gap between fundamental concepts and the fabrication of arbitrary atomic patterns in large scale, by providing unprecedented insight into the physics of structural phase transitions on the atomic scale.

The fields of organic electronics and spintronics have the potential to revolutionize the electronics industry. Finding the right materials that can retain their electrical and spin properties when combined is a technological and fundamental challenge. We carry out the study of three archetypal organic molecules in intimate contact with the BiAg2 surface alloy. We show that the BiAg2 alloy is an especially suited substrate due to its inertness as support for molecular films, exhibiting an almost complete absence of substrate-molecular interactions. This is inferred from the persistence of a completely unaltered giant spin-orbit split surface state of the BiAg 2 substrate, and from the absence of significant metallic screening of charged molecular levels in the organic layer. Spin-orbit split states in BiAg2 turn out to be far more robust to organic overlayers than previously thought. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Although noise is observed in many experiments, it is rarely used as a source of information. However, valuable information can be extracted from noisy signals. The motion of particles on a surface induced, for example, by thermal activation or by the interaction with the tip of a scanning tunnelling microscope may lead to fluctuations or switching of the tunnelling current. The analysis of these processes gives insight into dynamics on a single atomic or molecular level. Unfortunately, scanning tunnelling microscopy (STM) is not a useful tool to study dynamics in detail, as it is an intrinsically slow technique. Here, we show that this problem can be solved by providing a full real-time characterization of random telegraph noise in the current signal. The hopping rate, the noise amplitude and the relative occupation of the involved states are measured as a function of the tunnelling parameters, providing spatially resolved maps. In contrast to standard STM, our technique gives access to transiently populated states revealing an electron-driven hindered rotation between the equilibrium and two metastable positions of an individually adsorbed molecule. The new approach yields a complete characterization of copper phthalocyanine molecules on Cu(111), ranging from dynamical processes on surfaces to the underlying electronic structure on the single-molecule level. © 2013 Macmillan Publishers Limited. All rights reserved.

To be or not to be chlorinated: When octaethylporphyrin iron(III) chloride (FeOEP-Cl) molecules are sublimated onto Cu(111) surfaces, two different molecular species are observed through scanning tunneling microscopy, showing either a protrusion or a depression at the center. In combination with van der Waals-corrected density functional calculations, our experiments reveal that one species corresponds to FeOEP-Cl molecules with the chlorine atom pointing away from the surface, whereas the other species has been dechlorinated.

The rates of a hindered molecular rotation induced by tunneling electrons are evaluated using scattering theory within the sudden approximation. Our approach explains the excitation of copper phthalocyanine molecules (CuPc) on Cu(111) as revealed in a recent measurement of telegraph noise in a scanning tunneling microscopy experiment. A complete explanation of the experimental data is performed by computing the geometry of the adsorbed system, its electronic structure, and the energy transfer between tunneling electrons and the molecule's rotational degree of freedom. The results unambiguously show that tunneling electrons induce a frustrated rotation of the molecule. In addition, the theory determines the spatial distribution of the frustrated rotation excitation, confirming the striking dominance of two out of four molecular lobes in the observed excitation process. This lobe selectivity is attributed to the different hybridizations with the underlying substrate. © 2013 American Physical Society.

Biological and environmental changes are creating a growing demand for historical and global data sets. Comparing up-to-date ecological and biological findings with historical statements has become a major part of scientific work in the field of ecology. This evaluation and comparison procedure is very time-consuming while the availability of raw data is very low. Comparisons between original findings – if available – require a lot of work from print publication to digitalization or transformation to appropriate data formats. The effective use of working capacity is a general issue and has become important, should the use of information technologies be invoked to minimize time-wasting copy and paste operations. In this paper we aim to present a working repository for terrestrial biological data. The implementation of this type of data repository will provide various services to participating scientists as long as the final aim is the publication of these repositories. Furthermore, the security and long-term availability of environmental data is an issue of increasing importance to the scientific community. Unrepeatable sampling events and any data thus obtained are precious in time series analysis. For this reason, a well-structured storage of data is necessary for easy accessibility, retrieval and comparability. This is an important issue for the community of environmental scientists. The need to construct and implement repositories should prevail against all hitches and we are therefore describing our on-going task with the primary population of this kind of data repository. A biological and ecological information system is a matter of public interest and should also be a key issue for ecologists.

In der vorliegenden Arbeit wurde das hochgeordnete Wachstum von großen organischen Molekülen auf kristallinen Substraten mit Hilfe der Quaterrylenderivate QT, QTCDI und QTCMI untersucht. Um derartige Schichten herstellen und charakterisieren zu können, wurde eine Organische Molekularstrahlepitaxy (OMBE)-Anlage aufgebaut. Allerdings stellt OMBE bisher nur ein Standardverfahren für die Präparation hochgeordneter Schichten bestehend aus kleineren Molekülen dar. Im Zusammenhang mit größeren Molekülen ergibt sich die Frage, ob auf Grund der höheren Sublimationstemperatur diese unzersetzt aufgedampft werden können. Optische Spektroskopieexperimente haben gezeigt, daß dies im Fall von QT möglich ist. Andererseits beginnt die Zersetzung von QTCDI bereits unterhalb seiner Sublimationstemperatur, wobei als eines der Produkte QTCMI entsteht. Ein wesentliches Anliegen dieser Arbeit bestand darin, die Frage zu klären, inwieweit diese großen Aromate epitaktisch auf anorganischen als auch organischen Substraten aufwachsen. Organisch-anorganische Schichtsysteme wurden durch Aufdampfen der Quaterrylenderivate auf einkristalline, rekonstruierte Goldoberflächen erzeugt und anschließend mit LEED und STM charakterisiert. Trotz der eingeschränkten thermischen Stabilität von QTCDI konnten sowohl hochgeordnete QT als auch QTCDI Monolagen auf Au(111) hergestellt werden, die jeweils aus flachliegenden Molekülen bestehen. Im Falle von QTCDI konnte dieses Resultat durch eine Optimierung der Probenherstellung erreicht werden. Im Unterschied zur Anordnung der QT Moleküle in Reihen, bilden die QTCDI Moleküle eine dazu deutlich verschiedene brickwall Struktur, die durch die Bildung von Wasserstoffbrückenbindungen zwischen den Randgruppen der QTCDI Moleküle erklärt werden kann. In ähnlicher Weise zeigt sich der Einfluß der Substituenten auf die Anordnung der Moleküle in der Schicht an den gefunden QTCMI Strukturen. Im Unterschied zu QTCDI Monolagen auf Au(111), konnten keine reinen QTCMI Proben erz

Die Arbeit befasst sich mit der Erforschung und Anwendung der Kelvinsonden-Rasterkraftmikroskopie. Die Technik wird bezüglich der Quantität der gemessenen Werte und der erzielbaren lateralen Auflösung untersucht und auf diverse Probensysteme angewandt. Die so erhaltenen nanoskopischen Werte werden mit markoskopischen Messergebnissen verglichen. Sowohl die elektrostatische Kraft zwischen der Messspitze und der Probenoberfläche als auch deren Gradienten können zur Minimierung der elektrostatischen Wechselwirkung herangezogen werden. Die Detektion des Kraftgradienten zum Aufbau eines Regelkreises erweist sich gegenüber der Kraftdetektion überlegen. Die experimentell ermittelten Befunde werden durch eine Rechnersimulation bestätigt. Diese zeigt die Möglichkeit von quantitativen Ergebnissen für laterale Objektgrößen im Bereich von einigen Nanometern. Im Experiment kann dies gezeigt werden. Es folgt die Anwendung der Kelvinsonden-Rasterkraftmikroskopie: Nanoskopisch ermittelte Werte der Austrittsarbeitsänderung von Metalleinkristall-Oberflächen durch die Adsorption von C_60 entsprechen Literaturwerten, die mit makroskopisch messenden Methoden ermittelt wurden. Sich zeitlich ändernde Oberflächenpotentiale von einer organischen Solarzelle und von lateral unterschiedlich dotiertem Silizium lassen sich quantitativ messen. Der sich bei der Adsorption von Oktadezyl-Phosphonsäure auf Glimmer und Graphit bildende elektrostatische Dipol wird untersucht und abgebildet. Das Wachstumsverhalten und die Austrittsarbeit der organischen Moleküle PTCDA und Alq_3 auf den teilweise mit KBr bedeckten Metallsubstraten Au und Ag wird untersucht. Schlussendlich wird gezeigt, dass mit der Kelvinsonden-Rasterkraftmikroskopie sogar der molekülinterne Dipol der vier Butyl-Gruppen von Tetra-3,5-di-ter-butyl-phenyl-Porphyrinen aufgelöst werden kann.