• Charge Noise in Organic Electrochemical Transistors
    Stoop, Ralph L., Kishan Thodkar, Michele Sessolo, Henk J. Bolink, Christian Schoenenberger, and Michel Calame.
    Phys. Rev. Applied, 7, 14009 (2017). [DOI]
  • Protective effect of ultrathin alumina film against diffusion of iron into carbon fiber during growth of carbon nanotubes for hierarchical composites investigated by ptychographic X-ray computed tomography
    Szmyt, W., S. Vogel, A. Diaz, M. Holler, J. Gobrecht, M. Calame, and C. Dransfeld.
    Carbon, 115, 347-362 (2017). [DOI]

    Abstract Composite materials based on carbon fiber (CF) are prone to failure at the fiber-matrix interface upon compression or stress transverse to the fiber axis. The direct growth of carbon nanotubes on \{CF\} constitutes a novel approach to enhance the mechanical properties of the interface. However, the challenge is that, during the growth, tensile properties of the fiber are altered due to the diffusion effect of iron nanoparticles used in the process, leading to \{CF\} surface defect formation. In this work, we deliver and discuss an analysis methodology on ptychographic X-ray computed tomography (PXCT) images in order to assess the iron nanoparticle abundance within CFs. \{PXCT\} provides 50 nm – resolved 3D electron density maps of the CFs. We evidence the protective effect of an ultrathin alumina film against iron infiltration into \{CF\} during the \{CNT\} growth. This method potentially allows to evaluate the efficiency of other diffusion-minimizing approaches. The conclusions of the \{PXCT\} examination are validated by energy-dispersive X-ray spectroscopy and scanning transmission electron microscopy carried out on thin sample slices cut with a focused ion beam. The results provide a new insight into the mechanical performance of \{CFs\} and therefore constitute valuable knowledge for the development of hierarchical composites.

  • Comparative study of single and multi domain CVD graphene using large-area Raman mapping and electrical transport characterization
    Thodkar, Kishan, Maria El Abbassi, Felix Lüönd, Frédéric Overney, Christian Schoenenberger, Blaise Jeanneret, and Michel Calame.
    physica status solidi (RRL) – Rapid Research Letters, 10(11), 807-811 (2016). [DOI]
  • Active Surfaces as Possible Functional Systems in Detection and Chemical (Bio) Reactivity
    Housecroft, Catherine E., Cornelia G. Palivan, Karl Gademann, Wolfgang Meier, Michel Calame, Viktoria Mikhalevich, Xiaoyan Zhang, Ellen Piel, and Mathieu Szponarski<em>, et al</em>.
    Chimia, 70 (6), 402-412 (2016). [DOI]

    This article presents design strategies to demonstrate approaches to generate functionalized surfaces which have the potential for application in molecular systems; sensing and chemical reactivity applications are exemplified. Some applications are proven, while others are still under active investigation. Adaptation and extension of our strategies will lead to interfacing of different type of surfaces, specific interactions at a molecular level, and possible exchange of signals/cargoes between them. Optimization of the present approaches from each of five research groups within the NCCR will be directed towards expanding the types of functional surfaces and the properties that they exhibit.

  • Label-Free FimH Protein Interaction Analysis using Silicon Nanoribbon BioFETs
    Wipf, Mathias, Ralph L. Stoop, Giulio Navarra, Said Rabbani, Beat Ernst, Kristine Bedner, Christian Schoenenberger, and Michel Calame.
    ACS Sensors, 1 (6), 781–788 (2016). [DOI]

    The detection of biomarkers at very low concentration and low cost is increasingly important for clinical diagnosis. Moreover, monitoring affinities for receptor-antagonist interactions by time-resolved measurements is crucial for drug discovery and development. Biosensors based on ion-sensitive field-effect transistors (BioFETs) are promising candidates for being integrated into CMOS structures and cost-effective production. The detection of DNA and proteins with silicon nanowires has been successfully demonstrated using high affinity systems such as the biotin–streptavidin interaction. Here, we show the time-resolved label-free detection of the interaction of the bacterial FimH lectin with an immobilized mannose ligand on gold-coated silicon nanoribbon BioFETs. By comparing our results with a commercial state of the art surface plasmon resonance system, additional surface effects become visible when using this charge based detection method. Furthermore, we demonstrate the effect of sensor area on signal-to-noise ratio and estimate the theoretical limit of detection.

  • Implementing Silicon Nanoribbon Field-Effect Transistors as Arrays for Multiple Ion Detection
    Stoop, Ralph L., Mathias Wipf, Steffen Mueller, Kristine Bedner, Iain A. Wright, Colin J. Martin, Edwin C. Constable, Axel Fanget, and Christian Schoenenberger<em>, et al</em>.
    Biosensors, 6 (2), 21 (2016). [DOI]

    Ionic gradients play a crucial role in the physiology of the human body, ranging from metabolism in cells to muscle contractions or brain activities. To monitor these ions, inexpensive, label-free chemical sensing devices are needed. Field-effect transistors (FETs) based on silicon (Si) nanowires or nanoribbons (NRs) have a great potential as future biochemical sensors as they allow for the integration in microscopic devices at low production costs. Integrating NRs in dense arrays on a single chip expands the field of applications to implantable electrodes or multifunctional chemical sensing platforms. Ideally, such a platform is capable of detecting numerous species in a complex analyte. Here, we demonstrate the basis for simultaneous sodium and fluoride ion detection with a single sensor chip consisting of arrays of gold-coated SiNR FETs. A microfluidic system with individual channels allows modifying the NR surfaces with self-assembled monolayers of two types of ion receptors sensitive to sodium and fluoride ions. The functionalization procedure results in a differential setup having active fluoride- and sodium-sensitive NRs together with bare gold control NRs on the same chip. Comparing functionalized NRs with control NRs allows the compensation of non-specific contributions from changes in the background electrolyte concentration and reveals the response to the targeted species.

  • Additional peak appearing in the one-photon luminescence of single gold nanorods
    Froehlich, Toni, Christian Schoenenberger, and Michel Calame.
    Optics Letters, 41(7), 1325-1328 (2016). [DOI]

    We used a confocal laser microscope to investigate the one-photon photoluminescence (PL) of gold antennas.The PL spectra can precisely be fitted to a plasmon enhanced photoluminescence model. For increasing antenna length, the energy peak position decreases continuously until it reaches a value of 1.7 – 1.8 eV. For longer antennas and smaller plasmon energies, we observe an additional, persistent shoulder in the PL spectra, which we explain by a Gaussian-shaped peak at4X 1.78 – 1.79 eV. We attribute this behavior to the opening of an additional decay path for electrons at the gold interband transition edge which we observe only for long antennas.

  • Formation mechanism of metal-molecule-metal junctions: molecule-assisted migration on metal defects
    Thompson, D., J. Liao, N. Michael, A. J. Quinn, C. A. Nijhuis, C. O’Dwyer, P. N. Nirmalraj, C. Schoenenberger, and M. Calame.
    J. Phys. Chem. C, 119 (33), 19438-19451 (2015). [DOI]

    Activation energies, Ea, measured from molecular exchange experiments are combined with atomic-scale calculations to describe the migration of bare Au atoms and Au–alkanethiolate species on gold nanoparticle surfaces during ligand exchange for the creation of metal–molecule–metal junctions. It is well-known that Au atoms and alkanethiol–Au species can diffuse on gold with sub-1 eV barriers, and surface restructuring is crucial for self-assembled monolayer (SAM) formation for interlinking nanoparticles and in contacting nanoparticles to electrodes. In the present work, computer simulations reveal that naturally occurring ridges and adlayers on Au(111) are etched and resculpted by migration of alkanethiolate–Au species toward high coordination kink sites at surface step edges. The calculated energy barrier, Eb, for diffusion via step edges is 0.4–0.7 eV, close to the experimentally measured Ea of 0.5–0.7 eV. By contrast, putative migration from isolated nine-coordinated terrace sites and complete Au unbinding from the surface incur significantly larger barriers of +1 and +3 eV, respectively. Molecular van der Waals packing energies are calculated to have negligible effect on migration barriers for typically used molecules (length < 2.5 nm), indicating that migration inside SAMs does not change the size of the migration barrier. We use the computational methodology to propose a means of creating Au nanoparticle arrays via selective replacement of citrate protector molecules by thiocyanate linker molecules on surface step sites. This work also outlines the possibility of using Au/Pt alloys as possible candidates for creation of contacts that are well-formed and long-lived because of the superior stability of Pt interfaces against atomic migration.

  • Competing Surface Reactions Limiting the Performance of Ion-Sensitive Field-Effect Transistors
    Stoop, Ralph L., Mathias Wipf, Steffen Mueller, Kristine Bedner, Iain A. Wright, Colin J. Martin, Edwin C. Constable, Wangyang Fu, and Alexey Tarasov<em>, et al</em>.
    Sensors and Actuators B, 220, 500-507 (2015). [DOI]
  • Sensing with Advanced Computing Technology: Fin Field Effect Transistors with High-K Gate Stack on Bulk Silicon
    Rigante, Sara, Paolo Scarbolo, Mathias Wipf, Ralph L. Stoop, Kristine Bedner, Elizabeth Buitrago, Antonios Bazigos, Didier Bouvet, and Michel Calame<em>, et al</em>.
    ACS Nano, 9 (5), 4872-4881 (2015). [DOI]
  • Interplay Between Mechanical and Electronic Degrees of Freedom in pi-Stacked Molecular Junctions: From Single Molecules to Mesoscopic Nanoparticle Networks
    Ghane, Tahereh, Daijiro Nozaki, Arezoo Dianat, Anton Vladyka, Rafael Gutierrez, Jugun Prakash Chinta, Shlomo Yitzchaik, Michel Calame, and Gianaurelio Cuniberti.
    J. Phys. Chem. C, 119 (11), 6344-6355 (2015). [DOI]

    Functionalized nanoparticle networks offer a model system for the study of charge transport in low-dimensional systems as well as a potential platform to implement and test electronic functionalities. The electrical response of a nanoparticle network is expected to sensitively depend on the molecular inter-connects, i.e. on the linker chemistry. If these linkers have complex charge transport properties, then phenomenological models addressing the large scale properties of the network need to be complemented with microscopic calculations of the network building blocks. In this study we focus on the interplay between conformational fluctuations and electronic $\pi$-stacking in single molecule junctions and use the obtained microscopic information on their electrical transport properties to parametrize transition rates describing charge diffusion in mesoscopic nanoparticle networks. Our results point out at the strong influence of mechanical degrees of freedom on the electronic transport signatures of the studied molecules. This is then reflected in the varying charge diffusion at the network level. The modeling studies are complemented with first charge transport measurements at the single-molecule level of $\pi$-stacked molecular dimers using state of the art mechanically controllable break junction techniques in a liquid environment.

  • Spectroscopic ellipsometry on Si/SiO2/graphene tri-layer system exposed to downstream hydrogen plasma: Effects of hydrogenation and chemical sputtering
    Eren, Baran, Wangyang Fu, Laurent Marot, Michel Calame, Roland Steiner, and Ernst Meyer.
    Appl. Phys. Lett., 106, 11904 (2015). [DOI]

    In this work, the optical response of graphene to hydrogen plasma treatment is investigated with spectroscopic ellipsometry measurements.Although the electronic transport properties and Raman spectrum of graphene change after plasma hydrogenation, ellipsometric parameters of the Si/SiO2/graphene tri-layer system do not change.This is attributed to plasma hydrogenated graphene still being electrically conductive, since the light absorption of conducting 2D materials does not depend on the electronic band structure. A change in the light transmission can only be observed when higher energy hydrogen ions (30eV) are employed, which chemically sputter the graphene layer. An optical contrast is still apparent after sputtering due to the remaining traces of graphene and hydrocarbons on the surface. In brief, plasma treatment does not change the light transmission of graphene; and when it does, this is actually due to plasma damage rather than plasma hydrogenation.

  • Ordered nanoparticles arrays interconnected by molecular wires: electronic and optoelectronic properties
    Liao, J., S. Blok, S. J. van der Molen, S. Diefenbach, A. Holleitner, C. Schönenberger, A. Vladyka, and M. Calame.
    Chem. Soc. Rev., 44(4), 999-1014 (2015). [DOI]

    Arrays of metal nanoparticles in an organic matrix have attracted a lot of interest due to their diverse electronic and optoelectronic properties. Recent work demonstrates that nanoparticle arrays can be utilized as a template structure to incorporate single molecules. In this arrangement{,} the nanoparticles act as electronic contacts to the molecules. By varying parameters such as the nanoparticle material{,} the matrix material{,} the nanoparticle size{,} and the interparticle distance{,} the electronic behavior of the nanoparticle arrays can be substantially tuned and controlled. Furthermore{,} via the excitation of surface plasmon polaritons{,} the nanoparticles can be optically excited and electronically read-out. The versatility and possible applications of well-ordered nanoparticle arrays has been demonstrated by the realization of switching devices triggered optically or chemically and by the demonstration of chemical and mechanical sensing. Interestingly{,} hexagonal nanoparticle arrays may also become a useful platform to study the physics of collective plasmon resonances that can be described as Dirac-like bosonic excitations.

  • Random telegraph signals in molecular junctions
    Brunner, J., Teresa M. González, C. Schönenberger, and M. Calame.
    Journal of Physics: Cond. Matt., 26, 474202 (2014). [DOI]
  • Sensor system including silicon nanowire ion sensitive FET arrays and CMOS readout
    Livi, Paolo, Amir Shadmani, Mathias Wipf, Ralph L. Stoop, Joerg Rothe, Yihui Chen, Michel Calame, Christian Schoenenberger, and Andreas Hierlemann.
    Sensors and Actuators B: Chemical, 204, 568-577 (2014). [DOI]
  • Regulating a Benzodifuran Single Molecule Field Effect Transistor via Electrochemical Gating and Optimization of Molecule/Electrode Coupling
    Li, Zhihai, Hui Li, Songjie Chen, Toni Froehlich, Christian Schoenenberger, Michel Calame, Silvio Decurtins, Shi-Xia Liu, and Eric Borguet.
    J. Am. Chem. Soc., 136 (25), 8867-8870 (2014). [DOI]
  • High-yield fabrication of nm-size gaps in monolayer CVD graphene
    Nef, Cornelia, Laszlo Posa, Peter Makk, Wangyang Fu, Andras Halbritter, Christian Schönenberger, and Michel Calame.
    Nanoscale, 6, 7249-7254 (2014). [DOI]
  • Electrolyte gate dependent high-frequency measurement of graphene FETs for sensing applications
    Fu, W., El M. Abbassi, T. Hasler, M. Jung, M. Steinacher, M. Calame, and C. Schoenenberger.
    Appl. Phys. Lett., 104, 13102 (2014). [DOI]
  • Investigation of the dominant 1/f Noise Source in Silicon Nanowire Sensors
    Bedner, K., V. A. Guzenko, A. Tarasov, M. Wipf, R. Stoop, S. Rigante, J. Brunner, W. Fu, and C. David<em>, et al</em>.
    Sensors and Actuators B, 191, 270-275 (2014). [DOI]
  • pH- Response of Silicon Nanowire Sensors: Impact of Nanowire Width and Gate Oxide
    Bedner, K., V. A. Guzenko, A. Tarasov, M. Wipf, R. L. Stoop, D. Just, S. Rigante, W. Fu, and R. A. and Minamisawa<em>, et al</em>.
    Sensors and Materials, 25 (8), 567-576 (2013). [DOI]
  • High mobility graphene ion-sensitive field-effect transistors by noncovalent functionalization
    Fu, W., C. Nef, A. Tarasov, M. Wipf, R. Stoop, O. Knopfmacher, M. Weiss, M. Calame, and C. Schoenenberger.
    Nanoscale, 5, 12104-12110 (2013). [DOI]
  • Selective Sodium Sensing with Gold-Coated Silicon Nanowire Field-Effect Transistors in a Differential Setup
    Wipf, Mathias, Ralph L. Stoop, Alexey Tarasov, Kristine Bedner, Wangyang Fu, Iain A. Wright, Colin J. Martin, Edwin C. Constable, and Michel Calame<em>, et al</em>.
    ACS Nano, 7 (7), 5978-5983 (2013). [DOI]
  • Feature in "Visions for a molecular future" (Brief viewpoint on molecular electronics)
    Calame, Michel.
    Nature Nanotechnology, 8, 385-389 (2013). [DOI]
  • Hydrogen plasma microlithography of graphene supported on a Si/SiO2 substrate
    Eren, Baran, Thilo Glatzel, Marcin Kisiel, Wangyang Fu, Rémy Pawlak, Urs Gysin, Cornelia Nef, Laurent Marot, and Michel Calame<em>, et al</em>.
    Appl. Phys. Lett., 102, 71602 (2013). [DOI]
  • Understanding the Electrolyte Background for Biochemical Sensing with Ion-Sensitive Field-Effect Transistors
    Tarasov, A., M. Wipf, K. Bedner, J. Kurtz, Wangyang Fu, Vitaliy A. Guzenko, Oren Knopfmacher, Ralph L. Stoop, and Michel Calame<em>, et al</em>.
    ACS Nano, 6 (10), 9291-9298 (2012). [DOI]
  • Force-conductance correlation in individual molecular junctions
    Nef, C., P. L. T. M. Frederix, Jan Brunner, C. Schönenberger, and M. Calame.
    Nanotechnology, 23, 365201 (2012). [DOI]

    Conducting atomic force microscopy is an attractive approach enabling the correlation of mechanical and electrical properties in individual molecular junctions. Here we report on measurements of gold–gold and gold–octanedithiol–gold junctions. We introduce two-dimensional histograms in the form of scatter plots to better analyze the correlation between force and conductance. In this representation, the junction-forming octanedithiol compounds lead to a very clear step in the force–conductance data, which is not observed for control monothiol compounds. The conductance found for octanedithiols is in agreement with the idea that junction conductance is dominated by a single molecule.

  • SYMONE Project: Synaptic Molecular Networks for Bio-Inspired Information Processing
    Wendin, G., Dominique Vuillaume, M. Calame, S. Yitzchaik, Christian Gamrat, Gianaurelio Cuniberti, and V. Beiu.
    Int. J. Unconv. Comp., 8(4), 325-332 (2012).
  • A True Reference Nanosensor Realized with Silicon Nanowires
    Tarasov, A., M. Wipf, K. Bedner, J. Kurtz, Wangyang Fu, Vitaliy A. Guzenko, Oren Knopfmacher, Ralph L. Stoop, and Michel Calame<em>, et al</em>.
    Langmuir, 28 (25), 9899-9905 (2012). [DOI]

    Conventional gate oxide layers (e.g., SiO2, Al2O3, or HfO2) in silicon field-effect transistors (FETs) provide highly active surfaces, which can be exploited for electronic pH sensing. Recently, great progress has been achieved in pH sensing using compact integrateable nanowire FETs. However, it has turned out to be much harder to realize a true reference electrode, which – while sensing the electrostatic potential – does not respond to the proton concentration. In this work, we demonstrate a highly effective reference sensor, a so-called reference FET, whose proton sensitivity is suppressed by as much as 2 orders of magnitude. To do so, the Al2O3 surface of a nanowire FET was passivated with a self-assembled monolayer of silanes with a long alkyl chain. We have found that a full passivation can be achieved only after an extended period of self-assembling lasting several days at 80 °C. We use this slow process to measure the number of active proton binding sites as a function of time by a quantitative comparison of the measured nonlinear pH-sensitivities to a theoretical model (site-binding model). Furthermore, we have found that a partially passivated surface can sense small changes in the number of active binding sites reaching a detection limit of ?Ns ? 170 ?m–2Hz–1/2 at 10 Hz and pH 3.

  • Negative Differential Photoconductance in Gold Nanoparticle Arrays in the Coulomb Blockade Regime
    Mangold, Markus A., Michel Calame, Marcel Mayor, and Alexander W. Holleitner.
    ACS Nano, 6 (5), 4181-4189 (2012). [DOI]

    We investigate the photoconductance of gold nanoparticle arrays in the Coulomb blockade regime. Two-dimensional, hexagonal crystals of nanoparticles are produced by self-assembly. The nanoparticles are weakly coupled to their neighbors by a tunneling conductance. At low temperatures, the single electron charging energy of the nanoparticles dominates the conductance properties of the array. The Coulomb blockade of the nanoparticles can be lifted by optical excitation with a laser beam. The optical excitation leads to a localized heating of the arrays, which in turn gives rise to a local change in conductance and a redistribution of the overall electrical potential in the arrays. We introduce a dual-beam optical excitation technique to probe the distribution of the electrical potential in the nanoparticle array. A negative differential photoconductance is the direct consequence of the redistribution of the electrical potential upon lifting of the Coulomb blockade. On the basis of our model, we calculate the optically induced current from the dark current–voltage characteristics of the nanoparticle array. The calculations closely reproduce the experimental observations.

  • Silicon-based ISFET shows negligible dependence on salt concentration at constant pH
    Knopfmacher, Oren, Alexey Tarasov, Mathias Wipf, Wangyang Fu, Michel Calame, and Christian Schoenenberger.
    ChemPhysChem, 13 (5), 1157-1160 (2012). [DOI]

    The response of (miniaturized) ion-sensitive field-effect transistors (ISFETs) with oxide interfaces to changes in the electrolyte concentration is discussed. It is shown that FETs covered with a thin alumina layer are almost insensitive to changes in the ionic strength of the electrolyte, while being extremely pH-sensitive.

  • Graphene Transistors Are Insensitive to pH Changes in Solution
    Fu, Wangyang, Cornelia Nef, Oren Knopfmacher, Alexey Tarasov, Markus Weiss, Michel Calame, and Christian Schoenenberger.
    Nano Lett., 11 (9), 3597-3600 (2011). [DOI]

    We observe very small gate-voltage shifts in the transfer characteristic of as-prepared graphene field-effect transistors (GFETs) when the pH of the buffer is changed. This observation is in strong contrast to Si-based ion-sensitive FETs. The low gate-shift of a GFET can be further reduced if the graphene surface is covered with a hydrophobic fluorobenzene layer. If a thin Al-oxide layer is applied instead, the opposite happens. This suggests that clean graphene does not sense the chemical potential of protons. A GFET can therefore be used as a reference electrode in an aqueous electrolyte. Our finding sheds light on the large variety of pH-induced gate shifts that have been published for GFETs in the recent literature.

  • Resonant Photoconductance of Molecular Junctions Formed in Gold Nanoparticle Arrays
    Mangold, Markus A., Michel Calame, Marcel Mayor, and Alexander W. Holleitner.
    J. Am. Chem. Soc., 133 (31), 12185-12191 (2011). [DOI]
  • Signal-to-noise ratio in dual-gated silicon nanoribbon field-effect sensors
    Tarasov, A., W. Fu, O. Knopfmacher, J. Brunner, M. Calame, and C. Schoenenberger.
    Appl. Phys. Lett., 98, 12114 (2011). [DOI]

    Recent studies on nanoscale field-effect sensors reveal the crucial importance of the low-frequency noise for determining the ultimate detection limit. In this letter, the 1/f-type noise of Si nanoribbon field-effect sensors is investigated. We demonstrate that the signal-to-noise ratio can be increased by almost two orders of magnitude if the nanoribbon is operated in an optimal gate voltage range. In this case, the additional noise contribution from the contact regions is minimized, and an accuracy of 0.5‰ of a pH shift in 1 Hz bandwidth can be reached.

  • Quantitative Single-Molecule Detection at Ultralow Concentrations
    Haas, P., P. Then, A. Wild, W. Grange, S. Zorman, M. Hegner, M. Calame, U. Aebi, and J. Flammer<em>, et al</em>.
    Analytical Chemistry, 82 (14), 6299-6302 (2010). [DOI]
  • Molecular junctions: from tunneling to function
    Calame, Michel.
    CHIMIA Int. J. Chem, 64 (6), 391-397 (2010). [DOI]
  • Nernst Limit in Dual-Gated Si-Nanowire FET Sensors
    Knopfmacher, O., A. Tarasov, W. Fu, M. Wipf, B. Niesen, M. Calame, and C. Schönenberger.
    Nano Letters, 10, 2268-2274 (2010). [DOI]
  • Novel Cruciform Structures as Model Compounds for Coordination Induced Single Molecule Switches
    Grunder, Sergio, Roman Huber, Songmei Wu, Christian Schönenberger, Michel Calame, and Marcel Mayor.
    CHIMIA Int. J. Chem, 64, 140-144 (2010). [DOI]
  • Cyclic conductance switching in networks of redox-active molecular junctions
    Liao, J., J. S. Agustsson, S. Wu, O. Jeannin, Y. -F. Ran, S. -X. Liu, S. and Decurtins, Y. Leroux, and M. Mayor<em>, et al</em>.
    Nano Letters, 10 (3), 759-764 (2010). [DOI]
  • Oligoaryl Cruciform Structures as Model Compounds for Coordination-Induced Single-Molecule Switches
    Grunder, Sergio, Roman Huber, Songmei Wu, Christian Schönenberger, Michel Calame, and Marcel Mayor.
    Eur. J. Org. Chem., 5, 833-845 (2010). [DOI]
  • Dual Gated Silicon Nanowire Field Effect Transistors
    Knopfmacher, O., D. Keller, M. Calame, and C. Schönenberger.
    Procedia Chemistry, 1(1), 678-681 (2009). [DOI]
  • Surface Plasmon Enhanced Photoconductance of Gold Nanoparticle Arrays with Incorporated Alkane Linkers
    Mangold, M. A., C. Weiss, M. Calame, and A. W. Holleitner.
    Appl. Phys. Lett., 94, 161104 (2009). [DOI]

    We report on a photoconductive gain effect in two-dimensional arrays of gold nanoparticles (NPs) in which alkane molecules are inserted. The NP arrays are formed by a self-assembly process from alkanethiol-coated gold NPs, and subsequently they are patterned on a Si/SiO2 chip by a microcontact printing technique. We find that the photoconductance of the arrays is strongly enhanced at the frequency of the surface plasmon of the NPs. We interpret the observation as a bolometric enhancement in the conductance of the NP arrays upon excitation of the surface plasmon resonance

  • Molecular Junctions based on Aromatic Coupling
    Wu, S., M. -T. Gonzalez, R. Huber, S. Grunder, M. Mayor, Ch. Schoenenberger, and M. Calame.
    Swiss Physical Society Communications, 26, 10 (2009).

    If individual molecules are to be used as building blocks for electronic devices, it will be essential to understand charge transport at the level of single molecules. Most existing experiments rely on the synthesis of functional rod-like molecules with chemical linker groups at both ends to provide strong, covalent anchoring to the source and drain contacts. This approach has proved very successful, providing quantitative measures of single-molecule conductance, and demonstrating rectification and switching at the single-molecule level. However, the influence of intermolecular interactions on the formation and operation of molecular junctions has been overlooked. Here we report the use of oligophenylene ethynylene molecules as a model system, and establish that molecular junctions can still form when one of the chemical linker groups is displaced or even fully removed. Our results demonstrate that aromatic pi-coupling between adjacent molecules is efficient enough to allow for the controlled formation of molecular bridges between nearby electrodes.

  • Light-controlled conductance switching of ordered metal-molecule-metal devices
    van der Molen, S. J., J. Liao, T. Kudernac, J. S. Agustsson, L. Bernard, M. Calame, B. J. van Wees, B. Ferringa, and C. Schönenberger.
    Nano Letters, 9, 76-80 (2009). [DOI]
  • Scaling of 1/f noise in tunable break junctions
    Wu, Z. M., S. Wu, S. Oberholzer, M. Steinacher, M. Calame, and C. Schönenberger.
    Phys. Rev. B, 78, 235421 (2008). [DOI]
  • Molecular Junctions based on aromatic coupling
    Wu, Songmei, Roman Huber, Teresa M. Gonzalez, Sergio Grunder, Marcel Mayor, Christian Schönenberger, and Michel Calame.
    Nature Nanotechnology, 3(9), 569-574 (2008). [DOI]
  • Conductance values of alkanedithiol molecular junctions
    González, Teresa M., Jan Brunner, Roman Huber, Songmei Wu, Christian Schönenberger, and Michel Calame.
    New J. Phys., 10, 65018 (2008). [DOI]
  • Interlinking Au nanoparticles in 2D arrays via conjugated dithiolated molecules
    Liao, Jianhui, Markus Mangold, Sergio Grunder, Marcel Mayor, Christian Schönenberger, and Michel Calame.
    New J. Phys., 10, 65019 (2008). [DOI]
  • Detection of transient events in the presence of background noise
    Grange, W., P. Haas, A. Wild, A. Lieb, M. Hegner, M. Calame, and B. Hecht.
    J. Phys. Chem. B, 112, 7140 (2008). [DOI]
  • Electrical Conductance of Conjugated Oligomers at the Single Molecule Level
    Huber, R., M. T. Gonzalez, S. Wu, M. Langer, S. Grunder, V. Horhoiu, M. Mayor, M. R. Bryce, and C. Wang<em>, et al</em>.
    J. Am. Chem. Soc., 130(3), 1080-1084 (2008). [DOI]
  • Spectroscopy of Molecular Junction Networks Obtained by Place Exchange in 2D Nanoparticle Arrays
    Bernard, L., Y. Kamdzhilov, M. Calame, S. J. van der Molen, J. Liao, and C. Schönenberger.
    J. Phys. Chem. C, 111(50), 18445-18450 (2007). [DOI]
  • Tetrathiafulvalene-based moleculer electrical wires
    Giacalone, Francesco, Angeles M. Herranz, Lucia Grueter, Teresa M. Gonzalez, Michel Calame, Christian Schönenberger, Carlos R. Arroyo, Gabino Rubio-Bollinger, and Marisela Velez<em>, et al</em>.
    Chem. Comm., 46, 4854-4856 (2007). [DOI]
  • New Cruciform Structures: Toward Coordination Induced Single Molecule Switches
    Grunder, S., R. Huber, V. Horhoiu, M. T. Gonzalez, C. Schönenberger, M. Calame, and M. Mayor.
    J. Org. Chem., 72(22), 8337-8344 (2007). [DOI]
  • Feedback controlled electromigration in four-terminal nanojunctions
    Wu, Z. M., M. Steinacher, R. Huber, M. Calame, S. J. van der Molen, and C. Schönenberger.
    App. Phys. Lett., 91(5), 53118 (2007). [DOI]
  • Controlled formation of metallic nanowires via Au nanoparticle ac trapping
    Bernard, L., M. Calame, S. J. van der Molen, J. Liao, and C. Schönenberger.
    Nanotech., 18(23), 235202 (2007). [DOI]
  • Electrical conductance of molecular junctions by a robust statistical analysis
    González, Teresa M., Songmei Wu, Roman Huber, Sense Jan van der Molen, Christian Schönenberger, and Michel Calame.
    Nano Lett., 6(10), 2238-2242 (2006). [DOI]
  • Reversible formation of molecular junctions in 2D nanoparticles arrays
    Liao, Jianhui, Laetitia Bernard, Michael Langer, Christian Schönenberger, and Michel Calame.
    Adv. Mat., 18 (18), 2444-2447 (2006). [DOI]
  • Schaltende Moleküle
    Schoenenberger, Christian, Michel Calame, and Marcel Mayor.
    UniNova, Wissenschaftsmagazin der Universität Basel, 103, 22-24 (2006).
  • Molecular Electronics
    Calame, Michel and Christian Schoenenberger.
    Imaging & Microscopy, 8, 36 (2006). [DOI]
  • Building break junctions for molecular electronics
    Schoenenberger, Christian and Michel Calame.
    NanoNews, Newsletter of the NCCR Nanoscale Science, 01, 26-27 (2006).
  • Electrical conductance of atomic contacts in a liquid environment
    Grueter, Lucia, Teresa M. Gonzalez, Roman Huber, Michel Calame, and Christian Schönenberger.
    SMALL, 1(11), 1067-1070 (2005). [DOI]
  • Resonant tunnelling through a C60 molecular junction in a liquid environment
    Grueter, Lucia, Fuyong Cheng, Tero T. Heikkilä, M. Teresa Gonzalez, François Diederich, Christian Schönenberger, and Michel Calame.
    Nanotech., 16, 2143 (2005). [DOI]
  • Orientation and Positioning of DNA Molecules with an Electric Field Technique
    Dewarrat, F., M. Calame, and C. Schönenberger.
    Single Mol., 3(4), 189-193 (2002). [DOI]
  • Collective Pinning of a Frozen Vortex Liquid in Ultrathin Superconducting YBa2Cu3O7 films
    Calame, M., S. E. Korshunov, Ch. Leemann, and P. Martinoli.
    Phys. Rev. Lett., 86(16), 3630-3633 (2001). [DOI]
  • Single mismatch detection by gold-quenched fluorescent oligonucleotides
    Dubertret, B., M. Calame, and A. Libchaber.
    Nature Biotech., 19(4), 365-370 (2001). [DOI]
  • Dimensional crossover of the vortex matter in YBa2Cu3O7 thin films
    Calame, M., S. Blaser, Ch. Leemann, and P. Martinoli.
    Physica B, 284, 891-892 (2000). [DOI]
  • Measurement of the time evolution of mRNA level by RT-PCR and development of an RNA chip system for its direct measurement
    Sano, T., M. Calame, S. Liu, G. V. Shivashankar, and A. Libchaber.
    NEC Technical Report, 99, 138 (1999).
  • In-situ formation of one-dimensional coordination polymers in molecular junctions
    Vladyka, Anton, Mickael L. Perrin, Jan Overbeck, Rubén R. Ferradás, Víctor García-Suárez, Markus Gantenbein, Jan Brunner, Marcel Mayor, and Jaime Ferrer<em>, et al</em>.
    Nature Communications, 10(1), 262 (2019). [DOI]