T M Klapwijk
Delft University of Technology, Kavli Institute of Nanoscience, Faculty Member
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- Expert in mesoscopic and non equilibrium superconductivity, occasionally in combination with applications for astrono... moreExpert in mesoscopic and non equilibrium superconductivity, occasionally in combination with applications for astronomical instruments. Broadly interested in science within context. Has research experience at Delft, Harvard, Groningen, Santa Barbara, Caltech, Grenoble, Moscow, Würzburg and Donostia.edit
Last year I wrote a Master Thesis in the History and Philosophy of Science with the title: The Frisian Maasland wilderness and Lotharingian learning in the early 11th century. The article, based on this thesis, is about the very early... more
Last year I wrote a Master Thesis in the History and Philosophy of Science with the title: The Frisian Maasland wilderness and Lotharingian learning in the early 11th century. The article, based on this thesis, is about the very early influence of Arabic geometrical knowledge via Lorraine to the area south of Delft. From the perspective of the history of mathematics, it means a diffusion of knowledge through practice, a hundred years before translations from Arabic to Latin emerged. That is why it is also interesting as a cross-cultural phenomenon. In addition, it is a first report, that shows clearly how an astrolabe is useful for wetland surveying.
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Research Interests: Condensed Matter Physics, Materials Science, Chemistry, Field effect transistors, Medicine, and 15 moreMultidisciplinary, Nature, Electron, Organic Thin Film Transistor, Coulomb, Capacitance, Room Temperature, Single Crystal, First Order Logic, Charge Transport, Quantum Dot, Coulomb blockade, Low Temperature, ARRAYS, and Boltzmann constant
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Superconducting electronics has evolved primarily as a result of the discovery of Giaever tunneling and the Josephson effects. Originally both phenomena were dealt with in the framework of two superconductors separated by a thin... more
Superconducting electronics has evolved primarily as a result of the discovery of Giaever tunneling and the Josephson effects. Originally both phenomena were dealt with in the framework of two superconductors separated by a thin insulating layer. However, the Josephson effect is a much more general phenomenon which reveals the macroscopic quantum character of the superconducting state. Hence, the Josephson effect is found in a large variety of weak link structures such as superconductors connected by a narrow, short metallic contact (called a microbridge), by a normal metal, or by an insulator. In all cases the main features of the Josephson effect are present. The structures differ only with respect to the details of conduction of quasiparticles. The current-voltage characteristic is determined by the Josephson effect acting in parallel to a device-specific quasiparticle current. For various applications the response of either the quasiparticle current or the Josephson current is used. Which device is useful for which application depends on the required impedance, on an often needed nonlinearity and on the maximum supercurrent.
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Evaporation, Atomic Force Microscopy, and 10 moreTheoretical Morphology (in Biology), Thin Film, Sublimation, Pentacene, Thin Film Transistor, X ray diffraction, Single Crystal, Polycrystalline thin films, Film Thickness, and Lamellar Structure
Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Chemistry, Morphology, and 15 moreEvaporation, Atomic Force Microscopy, Growth, Thin Film, Oligothiophenes, Diffraction, Thin Film Transistor, Layered Structure, Room Temperature, Single Crystal, Organic Fet, Charge Transport, Single crystals, Crystallite, and Field effect transistor
Principles for obtaining high-quality rate control for electron gun evaporation are discussed. The design criteria for rate controllers are derived from this analysis. Results are presented which have been obtained with e-guns whose... more
Principles for obtaining high-quality rate control for electron gun evaporation are discussed. The design criteria for rate controllers are derived from this analysis. Results are presented which have been obtained with e-guns whose evaporation rate is controlled by a Wehnelt electrode or by sweeping of the electron beam. Further improvements of rate stability can be obtained by improved design of e-guns and power supplies.
Research Interests: Engineering, Nuclear Engineering, Physics, Materials Science, Quantum Mechanics, and 13 moreEvaporation, Molecular beam epitaxy, Scientific Instruments, Physical sciences, Electron Gun, Rate Control, Power Supply, CHEMICAL SCIENCES, Phase Transformation, Design Criteria, Electrode, Electron Beam, and Cathode Ray
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Thermodynamic measurements reveal that the Pauli spin susceptibility in a strongly correlated low-disorder two-dimensional electron system in silicon becomes enhanced by almost an order of magnitude at low electron densities and has a... more
Thermodynamic measurements reveal that the Pauli spin susceptibility in a strongly correlated low-disorder two-dimensional electron system in silicon becomes enhanced by almost an order of magnitude at low electron densities and has a critical behaviour close to the metal--insulator transition point. This provides thermodynamic evidence for the existence of a phase transition. The nature of the low-density phase still remains
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We have developed a 330-370GHz SIS mixer for small-format, heterodyne, astronomical imaging arrays. Fixed-tuned broadband operation is achieved by means of a superconducting radial waveguide probe. A horn-reflector antenna provides... more
We have developed a 330-370GHz SIS mixer for small-format, heterodyne, astronomical imaging arrays. Fixed-tuned broadband operation is achieved by means of a superconducting radial waveguide probe. A horn-reflector antenna provides high-efficiency optical coupling. Using a variable-temperature cryogenic noise source, we measured a DSB system noise temperature of 32±1K. The mixer contributes 3±3K, supporting the theoretically-predicted result that the noise temperature of a DSB mixer can be less than h?/2? (8.6K)
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We study the stability in time of the current–voltage characteristics of organic thin-film devices on glass substrates. We find for poly(3-hexylthiophene) and for pentacene that the resistance of the devices gradually changes under the... more
We study the stability in time of the current–voltage characteristics of organic thin-film devices on glass substrates. We find for poly(3-hexylthiophene) and for pentacene that the resistance of the devices gradually changes under the application of an electrical bias depending on the sodium content of the glass substrates used in the experiment. For devices on a very common type of glass (with a Na2O content of about 6%) and on sodalime glass (14% Na2O) substrates, the prolonged application of a voltage bias results in a substantial decrease (up to two orders of magnitude) of the bulk and contact resistances, whereas for sodium-free glass substrates the gradual changes in current–voltage characteristics are much smaller. A systematic study of the electrical behavior complemented by chemical analysis shows that the instabilities observed are due to Na+ ions diffusing from the substrate into the organic film, and moving inside the organic material as a result of the applied electric...
Research Interests: Engineering, Physics, Materials Science, Organic Semiconductors, Applied Physics, and 14 moreHysteresis, Electromigration, Molecular Electronics, Mathematical Sciences, Thin Film, Physical sciences, Impurity, Organic Semiconductor, Chemical Analysis, Pentacene, Contact Resistance, Electric Field, Organic Compound, and Current-Voltage Characteristic
We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. Both the receiver noise temperature and the gain bandwidth... more
We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. Both the receiver noise temperature and the gain bandwidth can be improved by a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we
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The influence of low energy (80–500 eV) Ar-ion milling cleaning techniques on InAs based quantum well structures is investigated. It is found that both etching with a Kaufmann source and sputter-etching with a rf-plasma enhances the... more
The influence of low energy (80–500 eV) Ar-ion milling cleaning techniques on InAs based quantum well structures is investigated. It is found that both etching with a Kaufmann source and sputter-etching with a rf-plasma enhances the electron density and reduces the mobility. An anneal at 180 °C has little effect, and only recovers damage caused by low energy (80 eV) Kaufmann etching.
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We have measured and analyzed the temperature and gate voltage dependencies of the field-effect mobility in organic thin-film transistors. We find that the mobility prefactor increases exponentially with the activation energy in agreement... more
We have measured and analyzed the temperature and gate voltage dependencies of the field-effect mobility in organic thin-film transistors. We find that the mobility prefactor increases exponentially with the activation energy in agreement with the Meyer–Neldel rule. This behavior is demonstrated in the mobility data of solution-processed pentacene, poly(2,5-thienylene vinylene) and in mobility data reported in literature. Surprisingly, the characteristic Meyer–Neldel energy for all analyzed materials is close to 40 meV. Possible implications for the charge transport mechanism in these materials are discussed.
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Rectification of microwave radiation (20-40 GHz) by a line boundary between two two-dimensional metals on a silicon surface was observed and investigated at different temperatures, in-plane magnetic fields and microwave powers. The... more
Rectification of microwave radiation (20-40 GHz) by a line boundary between two two-dimensional metals on a silicon surface was observed and investigated at different temperatures, in-plane magnetic fields and microwave powers. The rectified voltage $V_{dc}$ is generated whenever the electron densities $n_{1,2}$ of the two metals are different, changing polarity at $n_1 \approx n_2$. Very strong nonlinear response is found when one of the two 2D metals is close to the electron density corresponding to the reported magnetic instability in this system.
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We studied the properties of (Nb0.7,Ti0.3)N films deposited by reactive magnetron sputtering in an atmosphere of argon and nitrogen at ambient substrate temperature, with a particular focus on the technological factors that determine film... more
We studied the properties of (Nb0.7,Ti0.3)N films deposited by reactive magnetron sputtering in an atmosphere of argon and nitrogen at ambient substrate temperature, with a particular focus on the technological factors that determine film texture. The texture in the nitrides of transition metals determines many processes, including the wear resistance of tool coatings, diffusion in microelectronic devices, and the rate of chemical etching. Thus, since our goal is to use (Nb0.7,Ti0.3)N films in superconducting microelectronic devices, texture control is an essential element of our technology. We find that increasing the total gas pressure, while keeping the film chemical composition constant, results in a decrease in the ratio of the [200] and [111] x-ray diffraction (XRD) line intensities on Θ–2Θ Bragg–Brentano scans. Similar changes in XRD patterns are observed as the nitrogen injection increases for a constant sputtering pressure. In addition, XRD examination shows that some sampl...
Research Interests: Engineering, Physics, Materials Science, Thermodynamics, Microelectronics, and 15 moreApplied Physics, Titanium, Mathematical Sciences, Thin Film, Physical sciences, Nitrogen, Sputtering, Magnetron Sputtering, Residual Stress, Chemical Composition, Surface Energy, Sputter Deposition, Argon, Experimental Data, and Transition metal oxides
A generally applicable model is presented to describe the potential barrier shape in ultrasmall Schottky diodes. It is shown that for diodes smaller than a characteristic length lc (associated with the semiconductor doping level) the... more
A generally applicable model is presented to describe the potential barrier shape in ultrasmall Schottky diodes. It is shown that for diodes smaller than a characteristic length lc (associated with the semiconductor doping level) the conventional description no longer holds. For such small diodes the Schottky barrier thickness decreases with decreasing diode size. As a consequence, the resistance of the diode is strongly reduced, due to enhanced tunneling. Without the necessity of assuming a reduced (non-bulk) Schottky barrier height, this effect provides an explanation for several experimental observations of enhanced conduction in small Schottky diodes.