Dominic J Thurmer

Technische Universität Chemnitz, Karl-Marx-Stadt, Saxony, Germany

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Publications (22)158.88 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Bulky organic semiconductors have been widely applied on a variety of devices including transistors, sensors, and organic light-emitting diodes. Recently, the capability of producing stable ultrathin organic semiconductor-based junctions has opened the possibility of a variety of novel device concepts, including high-speed organic transistors, organic spin valves, and biosensors. In such context, the investigation of the charge transport mechanisms across ultrathin organic semiconductors is the key for the engineering of emerging organic-based technologies. Here, the charge transport mechanisms across heterojunctions based on physisorbed ultrathin copper phthalocyanine on gold are precisely determined and controlled over a wide range of temperatures and electric fields. We observe that the macroscopic electrical characteristics of Au/CuPc/Au heterojunctions are similar to what has been reported for chemisorbed molecular junctions. For instance, the transition from thermally activated transport to tunneling is verified regardless of the nature of the molecule-contact bonding. The Au/CuPc/Au heterojunction transport is dominated by charge localization sites at high temperatures and, upon cooling, a continuous transition from direct tunneling, via resonant tunneling, to field emission takes place by increasing the voltage bias. Such a continuous transition has not been reported for a hybrid metal/organic heterojunction yet. We have also determined the dielectric constant of the CuPc molecular layer via transport measurements, which allowed us to infer the possible molecule arrangements between the electrodes.
    The Journal of Physical Chemistry C 03/2014; 118(14):7272–7279. · 4.84 Impact Factor
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    ABSTRACT: The fabrication, characterization, and optimization of large area rolled-up ultracompact nanomembrane-based capacitor arrays is demonstrated by combining bottom-up and top-down fabrication methods. The scalability of the process is tested on a 4-inch wafer platform where 1600 devices are manufactured in parallel. By using a hybrid dielectric layer consisting of HfO2 and TiO2 incorporated into an Al2O3 matrix, rolled-up ultracompact capacitors can have their capacitance per footprint area increased by over two orders of magnitude. Their electrical properties can be precisely controlled by adjusting the oxide composition. Furthermore, the rolling of large-area nanomembrane-based structures naturally results in a substantial decrease of the occupied footprint area. Such electrostatic rolled-up ultracompact energy-storage elements have a large potential in powering various autonomous microsystems.
    Advanced Energy Materials 03/2014; · 14.39 Impact Factor
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    ABSTRACT: Pre-stressed multi-layer nanomembranes are rolled-up into a microtube in order to tune the strain applied to the contained coupled GaAs quantum wells. Additional GaAs/AlAs adjusting layers were deposited on the top of the nanomembrane to alter the thickness/stiffness of the to-be-rolled nanomembrane. In this way, microtubes with an adjustable diameter and strain are possible from a single initial grown sample. The internal strain state in the microtube affects the energy levels of the quantum wells and their coupling, which can be probed sensitively by photoluminescence. We measure different strain relaxation in rolled-up nanomembranes which we explain using a gradual change of the longitudinal relaxation as the distance of the nanomembrane from the etching front varies.
    Applied Physics Letters 01/2013; 102(4). · 3.52 Impact Factor
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    ABSTRACT: We fabricate inorganic thin film transistors with bending radii of less than 5μm maintaining their high electronic performance with on-off ratios of more than 100000 and subthreshold swings of 160mV/dec. The fabrication technology relies on the roll-up of highly strained semiconducting nanomembranes, which compacts planar transistors into three-dimensional tubular architectures opening intriguing potential for microfluidic applications. Our technique probes the ultimate limit for the bending radius of high performance thin film transistors.
    Nano Letters 12/2012; · 13.03 Impact Factor
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    ABSTRACT: Large arrays of multifunctional rolled-up semiconductors can be mass produced with precisely controlled size and composition, making them of great technological interest for micro- and nano-scale device fabrication. The microtube behavior at different temperatures is a key factor towards further engineering their functionality, as well as for characterizing strain, defects, and temperature-dependent properties of the structures. For this purpose, we probe optical phonons of GaAs/InGaAs rolled-up microtubes using Raman spectroscopy on defect-rich (faulty) and defect-free microtubes. The microtubes are fabricated by selectively etching an AlAs sacrificial layer in order to release the strained InGaAs/GaAs bilayer, all grown by molecular beam epitaxy. Pristine microtubes show homogeneity of the GaAs and InGaAs peak positions and intensities along the tube, which indicates a defect-free rolling up process, while for a cone-like microtube, a downward shift of the GaAs LO phonon peak along the cone is observed. Formation of other type of defects, including partially unfolded microtubes, can also be related to a high Raman intensity of the TO phonon in GaAs. We argue that the appearance of the TO phonon mode is a consequence of further relaxation of the selection rules due to the defects on the tubes, which makes this phonon useful for failure detection/prediction in such rolled up systems. In order to systematically characterize the temperature stability of the rolled up microtubes, Raman spectra were acquired as a function of sample temperature up to 300[degree sign]C. The reversibility of the changes in the Raman spectra of the tubes within this temperature range is demonstrated.
    Nanoscale Research Letters 10/2012; 7(1):594. · 2.52 Impact Factor
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    ABSTRACT: Here, we demonstrate the fabrication, characterization, and tailoring of porous organic nanomembranes and their direct integration on inorganic substrates for sensing applications. The chemically prepared nanomembranes can be integrated on both conducting and insulating substrates by either transfer or direct synthesis. We also successfully demonstrate their use for the detection of commonly used acids including HCl, H(2)SO(4), or H(3)PO(4) and their respective counterions, chlorides, sulfates, and phosphates. Impressively, the in situ acid detection is achieved down to 5 nmol·L(-1), while the quantification is feasible between 5 μmol·L(-1) and 10 mmol·L(-1). These values are among the lowest values reported so far in literature. Furthermore, the organic nanomembrane based sensor covers a wide concentration range of almost 8 orders of magnitude including the environmental limits currently adopted.
    Analytical Chemistry 08/2012; 84(19):8399-406. · 5.82 Impact Factor
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    ABSTRACT: Modifying the curvature in magnetic nanostructures is a novel and elegant way toward tailoring physical phenomena at the nanoscale, allowing one to overcome limitations apparent in planar counterparts. Here, we address curvature-driven changes of static magnetic properties in cylindrically curved magnetic segments with different radii of curvature. The curved architectures are prepared by capping nonmagnetic micrometer- and nanometer-sized rolled-up membranes with a soft-magnetic 20 nm thick permalloy (Ni(80)Fe(20)) film. A quantitative comparison between the magnetization reversal processes in caps with different diameters is given. The phase diagrams of magnetic equilibrium domain patterns (diameter versus length) are generated. For this, joint experimental, including X-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM), and theoretical studies are carried out. The anisotropic magnetostatic interaction in cylindrically curved architectures originating from the thickness gradient reduces substantially the magnetostatic interaction between closely packed curved nanowires. This feature is beneficial for racetrack memory devices, since a much higher areal density might be achieved than possible with planar counterparts.
    Nano Letters 06/2012; 12(8):3961-6. · 13.03 Impact Factor
  • physica status solidi (b) 04/2012; 249(4):687-696. · 1.49 Impact Factor
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    ABSTRACT: In this work, we combine self-assembly and top-down methods to create hybrid junctions consisting of single organic molecular monolayers sandwiched between metal and/or single-crystalline semiconductor nanomembrane based electrodes. The fabrication process is fully integrative and produces a yield loss of less than 5% on-chip. The nanomembrane-based electrodes guarantee a soft yet robust contact to the molecules where the presence of pinholes and other defects becomes almost irrelevant. We also pioneer the fabrication and characterization of semiconductor/molecule/semiconductor tunneling heterojunctions which exhibit a double transition from direct tunneling to field emission and back to direct tunneling, a phenomenon which has not been reported previously.
    Nano Letters 08/2011; 11(9):3727-33. · 13.03 Impact Factor
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    ABSTRACT: A new method for combining top-down and bottom-up approaches to create superconductor-normal metal-superconductor niobium-based Josephson junctions is presented. Using a rolled-up semiconductor nanomembrane as scaffolding, we are able to create mesoscopic gold filament proximity junctions. These are created by electromigration of gold filaments after inducing an electric field mediated breakdown in the semiconductor nanomembrane, which can generate nanometer sized structures merely using conventional optical lithography techniques. We find that the created point contact junctions exhibit large critical currents of a few milliamps at 4.2 K and an I(c)R(n) product placing their characteristic frequency in the terahertz region. These nanometer-sized filament devices can be further optimized and integrated on a chip for their use in superconductor hybrid electronics circuits.
    Nano Letters 09/2010; 10(9):3704-9. · 13.03 Impact Factor
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    ABSTRACT: Self-assembly methods combined with standard top-down approaches are demonstrated to be suitable for fabricating three-dimensional ultracompact hybrid organic/inorganic electronic devices based on rolled-up nanomembranes. Capacitors that are self-wound and manufactured in parallel are almost 2 orders of magnitude smaller than their planar counterparts and exhibit capacitances per footprint area of around 200 microF/cm(2). This value significantly exceeds that which was previously reported for metal-insulator-metal capacitors based on Al(2)O(3), and the obtained specific energy (approximately 0.55 Wh/kg) would allow their usage as ultracompact supercapacitors. By incorporating organic monolayers into the inorganic nanomembrane structure we can precisely control the electronic characteristics of the devices. The adaptation of the process for creating ultracompact batteries, coils and transformers is an attractive opportunity for reducing the size of energy storage elements, filters, and signal converters. These devices can be employed as implantable electronic circuits or new approaches for energy-harvesting applications. Furthermore, the incorporation of functional organic molecules gives rise to novel devices with almost limitless chemical and biological functionalities.
    Nano Letters 07/2010; 10(7):2506-10. · 13.03 Impact Factor
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    ABSTRACT: The alignment behavior of solution dispersed rolled-up microtubes by surface acoustic waves (SAW) is demonstrated. In contrast to the random alignment of rolled-up insulated silicon oxide tubes, metallic chromium tubes can be effectively aligned and assembled into "tube-chains" parallel to the SAW propagation direction. The experiments suggest that the tube orientation is mainly determined by the dielectrophoresis (DEP) forces acting on the tubes. The DEP forces arise from the induced dipole moment of the tubes in the SAW generated piezoelectric field on the LiNbO3 substrate.
    Applied Physics Letters 01/2010; 96(13). · 3.52 Impact Factor
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    ABSTRACT: Ultrathin AlN/GaN crystalline porous freestanding nanomembranes are fabricated on Si(111) by selective silicon etching, and self-assembled into various geometries such as tubes, spirals, and curved sheets. Nanopores with sizes from several to tens of nanometers are produced in nanomembranes of 20-35 nm nominal thickness, caused by the island growth of AlN on Si(111). No crystal-orientation dependence is observed while releasing the AlN/GaN nanomembranes from the Si substrate indicating that the driving stress mainly originates from the zipping effect among islands during growth. Competition between different relaxation mechanisms is experimentally revealed for different nanomembrane geometries and well-described by numerical calculations. The cathodoluminescence emission from GaN nanomembranes reveals a weak peak close to the GaN bandgap, which is dramatically enhanced by electron irradiation.
    ACS Nano 07/2009; 3(7):1663-8. · 12.03 Impact Factor
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    ABSTRACT: Transparent oxide rolled-up microtube arrays were constructed on Si substrates by the deposition of a pre-stressed oxide layer on a patterned photoresist sacrificial layer and the subsequent removal of this sacrificial layer. These microtubes as well as their arrays can be well positioned onto a chip for further applications, while their dimensions (e.g. length, diameter and wall thickness) are controlled by tunable parameters of the fabrication process. Due to the unique tubular structure and optical transparency, such rolled-up microtubes can serve as well-defined two-dimensionally (2D) confined cell culture scaffolds. In our experiments, yeast cells exhibit different growth behaviors (i.e. their arrangement) in microtubes with varied diameters. In an extremely small microtube the yeast cell becomes highly elongated during growth but still survives. Detailed investigations on the behavior of individual yeast cells in a single microtube are carried out in situ to elucidate the mechanical interaction between microtubes and the 2D confined cells. The confinement of tubular channels causes the rotation of cell pairs, which is more pronounced in smaller microtubes, leading to different cellular assemblies. Our work demonstrates good capability of rolled-up microtubes for manipulating individual and definite cells, which promises high potential in lab-on-a-chip applications, for example as a bio-analytic system for individual cells if integrated with sensor functionalities.
    Lab on a Chip 03/2009; 9(2):263-8. · 5.70 Impact Factor
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    ABSTRACT: The effect of illumination on the hydrofluoric acid etching of AlAs sacrificial layers with systematically varied thicknesses in order to release and roll up InGaAs/GaAs bilayers was studied. For thicknesses of AlAs below 10 nm, there were two etching regimes for the area under illumination: one at low illumination intensities, in which the etching and releasing proceeds as expected and one at higher intensities in which the etching and any releasing are completely suppressed. The "etch suppression" area is well defined by the illumination spot, a feature that can be used to create heterogeneously etched regions with a high degree of control, shown here on patterned samples. Together with the studied self-limitation effect, the technique offers a way to determine the position of rolled-up micro- and nanotubes independently from the predefined lithographic pattern.
    Nanoscale Research Letters 01/2009; 4(12):1463-8. · 2.52 Impact Factor
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    ABSTRACT: The authors fabricate rolled up microtubes consisting of Si/SiOx on Si substrate and analyze the possibility to use them as a refractometric sensor. An aqueous sugar solution is inserted into the microtube, which leads to a change in refractive index and, as a result, to a detectable spectral shift of the whispering gallery modes. Experimental results can fit well with finite-difference time-domain simulations, which are used to determine the sensitivity of this tube refractometer. The ratio of spectral sensitivity to channel cross-sectional area of the refractometer is particularly striking and allows analysis of fluid volumes in the range of femtoliters. A comparative discussion with other existing refractometer schemes concludes this work.
    Applied Physics Letters 09/2008; 93(9):094106-094106-3. · 3.52 Impact Factor
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    ABSTRACT: We preformed a numerical investigation of the optical mode in rolled-up microtube resonators. The optical responses of the self-rolling semiconductor-based resonators are calculated by solving Maxwell’s equations using the finite-difference time-domain (FDTD) method. Observed mode patterns characterized by whispering-gallery-mode-like profile are presented with various sets of structural parameters (tube diameter, tube wall thickness, and the number of rotation). The degeneracy breaking results in splitting of the mode peaks with the same azimuthal mode index is observed and we confirmed that it causes by structural asymmetry of the rolled-up structure. For the rolled-up tube with thick tube wall, the quasi-whispering gallery mode pattern due to very high degree of structural asymmetry is shown. In this presentation, we also propose an application of the rolled-up microtube as a refractometric sensor. For this proposal, we experimentally fill the rolled-up tube with liquid and measure the mode peaks shift due to the change of refractive index inside the tube. A FDTD simulation with realistic structural parameters fits well with the experimental spectra. The field shows more leaky to the inner part of the tube due to the increase of the refractive index. High spectral sensitivity is obtained from the tube with thin-wall structure at the long wavelength peak with low azimuthal mode index. This is due to the large overlap between the leakage field and the liquid for the lower mode index. However, the quality factor considerably drops when the wall is very thin. Rolled-up tube with larger number of rotation has lower sensitivity as effectively similar to the tube with thicker wall.
    Transparent Optical Networks, 2008. ICTON 2008. 10th Anniversary International Conference on; 07/2008
  • D. J. Thurmer, C. Deneke, O. G. Schmidt
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    ABSTRACT: A complex rolling behaviour for InGaAs/GaAs/Nb trilayer microtubes is reported. Video microscopy of the rolling process unveils a variety of movements present in this material system including upward rolling, unrolling, wrinkling and downward rolling of a nanomembrane. Using transmission electron microscopy, cross-sections of the layer system are analysed, and a model for the rolling is presented. Through this study, a unique way to determine the direction and magnitude of strain gradients within a layer system is demonstrated.
    Journal of Physics D Applied Physics 01/2008; 41(20):5. · 2.53 Impact Factor
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    ABSTRACT: we demonstrate a technology "Release and bond-back of layers (REBOLA)" that exploits the deterministic wrinkling of a semiconductor layer to create well-defined and versatile nanochannel networks. In linear networks, the periodicity of branch channels as a function of etch-width was analyzed and compared with theoretical calculations. A self-similar folding phenomenon of wrinkles near a fixed boundary was revealed by autocorrelation analysis. The formation of branch channels within circular networks was studied on different length scales and was controlled by the size of the etched circular network and the shape of the initial pattern. To elucidate the usefulness of REBOLA, we exemplified nanofluidic transport as well as femto-litre filling and emptying of individual wrinkles on a standard semiconductor substrate, in which corner flow played an important role.
    Advanced Materials 07/2007; 19(16):2124 - 2128. · 14.83 Impact Factor
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    ABSTRACT: A wrinkled nanomembrane with embedded quantum well (QW), fabricated by the partial release and bond back of epitaxial layers upon underetching, is investigated by spatially resolved micro-photoluminescence spectroscopy. From the observed QW transition energies and calculations based on the linear deformation potential theory, we find that the bonded back regions are fully relaxed and act on the strain state of the wrinkled QW. Light emission enhancement observed in the wrinkled QW is explained by interference contrast theory.
    Nano Letters 07/2007; 7(6):1676-9. · 13.03 Impact Factor

Publication Stats

193 Citations
158.88 Total Impact Points

Institutions

  • 2012
    • Technische Universität Chemnitz
      • Chair of Materials for Nanoelectronics
      Karl-Marx-Stadt, Saxony, Germany
  • 2009–2012
    • Leibniz Institute for Solid State and Materials Research Dresden
      • Institute for Integrative Nanosciences
      Dresden, Saxony, Germany
  • 2007
    • Max Planck Institute for Solid State Research
      Stuttgart, Baden-Württemberg, Germany