liu.seSearch for publications in DiVA
Change search
Refine search result
1234 1 - 50 of 170
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Abdalla, Hassan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Investigation of the dimensionality of charge transport in organic field effect transistors2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 8, article id 85301Article in journal (Refereed)
    Abstract [en]

    Ever since the first experimental investigations of organic field effect transistors (OFETs) the dimensionality of charge transport has alternately been described as two dimensional (2D) and three dimensional (3D). More recently, researchers have turned to an analytical analysis of the temperature-dependent transfer characteristics to classify the dimensionality as either 2D or 3D as well as to determine the disorder of the system, thereby greatly simplifying dimensionality investigations. We applied said analytical analysis to the experimental results of our OFETs comprising molecularly well-defined polymeric layers as the active material as well as to results obtained from kinetic Monte Carlo simulations and found that it was not able to correctly distinguish between 2D and 3D transports or give meaningful values for the disorder and should only be used for quasiquantitative and comparative analysis. We conclude to show that the dimensionality of charge transport in OFETs is a function of the interplay between transistor physics and morphology of the organic material.

  • 2.
    Abdalla, Hassan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    van de Ruit, Kevin
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, Netherlands.
    Effective Temperature and Universal Conductivity Scaling in Organic Semiconductors2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 16870Article in journal (Refereed)
    Abstract [en]

    We investigate the scalability of the temperature-and electric field-dependence of the conductivity of disordered organic semiconductors to universal curves by two different but commonly employed methods; by so-called universal scaling and by using the effective temperature concept. Experimentally both scaling methods were found to be equally applicable to the out-of-plane charge transport in PEDOT: PSS thin films of various compositions. Both methods are shown to be equivalent in terms of functional dependence and to have identical limiting behavior. The experimentally observed scaling behavior can be reproduced by a numerical nearest-neighbor hopping model, accounting for the Coulomb interaction, the high charge carrier concentration and the energetic disorder. The underlying physics can be captured in a simple empirical model, describing the effective temperature of the charge carrier distribution as the outcome of a heat balance between Joule heating and (effective) temperature-dependent energy loss to the lattice.

  • 3.
    Abdalla, Hassan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Zuo, Guangzheng
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Range and energetics of charge hopping in organic semiconductors2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 24, article id 241202Article in journal (Refereed)
    Abstract [en]

    The recent upswing in attention for the thermoelectric properties of organic semiconductors (OSCs) adds urgency to the need for a quantitative description of the range and energetics of hopping transport in organic semiconductors under relevant circumstances, i.e., around room temperature (RT). In particular, the degree to which hops beyond the nearest neighbor must be accounted for at RT is still largely unknown. Here, measurements of charge and energy transport in doped OSCs are combined with analytical modeling to reach the univocal conclusion that variable-range hopping is the proper description in a large class of disordered OSC at RT. To obtain quantitative agreement with experiment, one needs to account for the modification of the density of states by ionized dopants. These Coulomb interactions give rise to a deep tail of trap states that is independent of the materials initial energetic disorder. Insertion of this effect into a classical Mott-type variable-range hopping model allows one to give a quantitative description of temperature-dependent conductivity and thermopower measurements on a wide range of disordered OSCs. In particular, the model explains the commonly observed quasiuniversal power-law relation between the Seebeck coefficient and the conductivity.

  • 4.
    Andringa, Anne-Marije
    et al.
    University of Groningen, Netherlands; Philips Research Labs, Netherlands.
    Christian Roelofs, W. S.
    Philips Research Labs, Netherlands; Technical University of Eindhoven, Netherlands.
    Sommer, Michael
    University of Bayreuth, Germany; University of Freiburg, Germany.
    Thelakkat, Mukundan
    University of Bayreuth, Germany.
    Kemerink, Martijn
    Technical University of Eindhoven, Netherlands.
    de Leeuw, Dago M.
    University of Groningen, Netherlands; Philips Research Labs, Netherlands.
    Localizing trapped charge carriers in NO2 sensors based on organic field-effect transistors2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 15, article id 153302Article in journal (Refereed)
    Abstract [en]

    Field-effect transistors have emerged as NO2 sensors. The detection relies on trapping of accumulated electrons, leading to a shift of the threshold voltage. To determine the location of the trapped electrons we have delaminated different semiconductors from the transistors with adhesive tape and measured the surface potential of the revealed gate dielectric with scanning Kelvin probe microscopy. We unambiguously show that the trapped electrons are not located in the semiconductor but at the gate dielectric. The microscopic origin is discussed. Pinpointing the location paves the way to optimize the sensitivity of NO2 field-effect sensors. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4758697]

  • 5.
    Asadi, Kamal
    et al.
    Philips Research Labs, Netherlands.
    Li, Mengyuan
    University of Groningen, Netherlands.
    Blom, Paul W. M.
    University of Groningen, Netherlands; Holst Centre, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    de Leeuw, Dago M.
    Philips Research Labs, Netherlands; University of Groningen, Netherlands.
    Organic ferroelectric opto-electronic memories2011In: Materials Today, ISSN 1369-7021, E-ISSN 1873-4103, Vol. 14, no 12, p. 592-599Article, review/survey (Refereed)
    Abstract [en]

    Organic electronics have emerged as a promising technology for large-area micro-electronic applications, such as rollable displays(1), electronic paper(2), contactless identification transponders(3,4), and smart labels(5). Most of these applications require memory functions; preferably a non-volatile memory that retains its data when the power is turned off, and that can be programmed, erased, and read-out electrically.

  • 6.
    Balke, Nina
    et al.
    Oak Ridge National Lab, TN 37831 USA.
    Bonnell, Dawn
    University of Penn, PA 19104 USA.
    Ginger, David S.
    University of Washington, WA 98195 USA.
    Kemerink, Martijn
    Technical University of Eindhoven, Netherlands.
    Scanning probes for new energy materials: Probing local structure and function2012In: MRS bulletin, ISSN 0883-7694, E-ISSN 1938-1425, Vol. 37, no 7, p. 633-637Article in journal (Refereed)
    Abstract [en]

    The design and control of materials properties, often at the nanoscale, are the foundation of many new strategies for energy generation, storage, and efficiency. Scanning probe microscopy (SPM) has evolved into a very large toolbox for the characterization of properties spanning size scales from hundreds of microns to nanometers. Recent advances in SPM involve properties and size scales of precise relevance to energy-related materials, as presented in this issue. These advances are put into the general context of energy research, and the general principles are summarized.

  • 7.
    Beek, WJE
    et al.
    Eindhoven University of Technology, Netherlands.
    Wienk, MM
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Yang, XN
    Eindhoven University of Technology, Netherlands.
    Janssen, RAJ
    Eindhoven University of Technology, Netherlands.
    Hybrid zinc oxide conjugated polymer bulk heterojunction solar cells2005In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 109, no 19, p. 9505-9516Article in journal (Refereed)
    Abstract [en]

    Bulk heterojunction photovoltaic devices based on blends of a conjugated polymer poly [2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) as electron donor and crystalline ZnO nanoparticles (nc-ZnO) as electron acceptor have been studied. Composite nc-ZnO:MDMO-PPV films were cast from a common solvent mixture. Time-resolved pump-probe spectroscopy revealed that a photoinduced electron transfer from MDMO-PPV to nc-ZnO occurs in these blends on a sub-picosecond time scale and produces a long-lived (milliseconds) charge-separated state. The photovoltaic effect in devices, made by sandwiching the active nc-ZnO:MDMO-PPV layer between charge-selective electrodes, has been studied as a function of the ZnO concentration and the thickness of the layer. We also investigated changing the degree and type of mixing of the two components through the use of a surfactant for ZnO and by altering the size and shape of the nc-ZnO particles. Optimized devices have an estimated AM1.5 performance of 1.6% with incident photon to current conversion efficiencies up to 50%. Photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy have been used to gain insight in the morphology of these blends.

  • 8.
    Bernard, L.
    et al.
    Empa, Switzerland; Eindhoven University of Technology, Netherlands.
    Khikhlovskyi, V.
    TNO Dutch Org Appl Science Research, Netherlands.
    van Breemen, A.
    TNO Dutch Org Appl Science Research, Netherlands.
    Michels, J. J.
    Max Planck Institute Polymer Research, Germany.
    Janssen, R.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, Netherlands.
    Gelinck, G.
    Eindhoven University of Technology, Netherlands; TNO Dutch Org Appl Science Research, Netherlands.
    Pilet, N.
    Paul Scherrer Institute, Switzerland.
    Study of the morphology of organic ferroelectric diodes with combined scanning force and scanning transmission X-ray microscopy2018In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 53, p. 242-248Article in journal (Refereed)
    Abstract [en]

    Organic ferroelectric diodes attract increasing interest as they combine non-destructive data read-out and low cost fabrication, two requirements in the development of novel non-volatile memory elements. The macroscopic electrical characteristics and performances of such devices strongly depend on their structural properties. Various studies of their global microscopic morphology have already been reported. Here, a multi-technique approach including different scanning force and X-ray microscopies permitted to reveal and locally study nanometer-scale unexpected sub-structures within a P(VDF-TrFE):F8BT ferroelectric diode. The strong impact of these structures on the local polarizability of the ferroelectric is shown. Two alternative fabrication methods are proposed that prevent the formation of these structures and demonstrate improved macroscopic device performances such as endurance and ON/OFF ratio.

    The full text will be freely available from 2019-12-05 16:28
  • 9.
    Bloom, F. L.
    et al.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Wagemans, W.
    Eindhoven University of Technology, Netherlands.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands.
    Sign Inversion of Magnetoresistance in Space-Charge Limited Organic Devices2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 6, article id 066601Article in journal (Refereed)
    Abstract [en]

    In this Letter, we explain the puzzling sign change of organic magnetoresistance in space-charge limited devices by device physics. We prove analytically and numerically that in the case of bipolar conduction with an Ohmic majority carrier and an injection limited minority carrier contact, a decrease in minority carrier mobility may give rise to an increase in the device current. It is shown that when the magnetic field acts to decrease the mobility of both carriers, a sign change in the magnetoconductivity as a function of applied bias may result. This behavior is in agreement with experimental observations.

  • 10.
    Bloom, F. L.
    et al.
    Eindhoven University of Technology, Netherlands.
    Wagemans, W.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands.
    Correspondence of the sign change in organic magnetoresistance with the onset of bipolar charge transport2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 26, article id 263302Article in journal (Refereed)
    Abstract [en]

    In this work we examine the transition between positive and negative organic magnetoresistance in poly[2-methoxy-5-(3(), 7()-dimethyloctyloxy)-p-phenylenevinylene] in order to understand how different regimes of charge transport affect the organic magnetoresistance effect. To characterize the charge transport in these devices we measured the current, low frequency differential capacitance, and electroluminescence efficiency as a function of voltage. These measurements show that the sign change of the magnetoresistance corresponds with a change from a unipolar diffusive transport below the built in voltage (V(bi)) to a regime of bipolar drift transport above V(bi).

  • 11.
    Bloom, F. L.
    et al.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Wagemans, W.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Separating positive and negative magnetoresistance in organic semiconductor devices2007In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 99, no 25, article id 257201Article in journal (Refereed)
    Abstract [en]

    We study the transition between positive and negative organic magnetoresistance (OMAR) in tris-(8 hydroxyquinoline) aluminium (Alq(3)), in order to identify the elementary mechanisms governing this phenomenon. We show how the sign of OMAR changes as function of the applied voltage and temperature. The transition from negative to positive magnetoresistance (MR) is found to be accompanied by an increase in slope of log(I) versus log(V). ac admittance measurements show this transition coincides with the onset of minority charge (hole) injection in the device. All these observations are consistent with two simultaneous contributions with opposite sign of MR, which may be assigned to holes and electrons having different magnetic field responses.

  • 12.
    Bobbert, PA
    et al.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Koenraad, PM
    Eindhoven University of Technology, Netherlands.
    Density functional theory for holes in semiconductors1998In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 80, no 14, p. 3159-3159Article in journal (Refereed)
    Abstract [en]

    n/a

  • 13.
    Bobbert, PA
    et al.
    COBRA Interuniversitary Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Wieldraaijer, H
    COBRA Interuniversitary Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.
    van der Weide, R
    COBRA Interuniversitary Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Kemerink, Martijn
    COBRA Interuniversitary Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Koenraad, PM
    COBRA Interuniversitary Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Wolter, JH
    COBRA Interuniversitary Research Institute, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Exchange-correlation energy of a hole gas including valence band coupling1997In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 56, no 7, p. 3664-3671Article in journal (Refereed)
    Abstract [en]

    We have calculated an accurate exchange-correlation energy of a hole gas, including the complexities related to the valence band coupling as occurring in semiconductors like GaAs, but excluding the band warping. A parametrization for the dependence on the density and the ratio between light-and heavy-hole masses is given. We apply our results to a hole gas in an AlxGa1-xAs/GaAs/AlxGa1-xAs quantum well and calculate the two-dimensional band structure and the band-gap renormalization. The inclusion of the valence band coupling in the calculation of the exchange-correlation potentials for holes and electrons leads to a much better agreement between theoretical and experimental data than when it is omitted.

  • 14.
    Bobbert, Peter A.
    et al.
    Eindhoven University of Technology, Netherlands.
    Sharma, Abhinav
    Eindhoven University of Technology, Netherlands.
    Mathijssen, Simon G. J.
    Eindhoven University of Technology, Netherlands; Philips Research Labs, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    de Leeuw, Dago M.
    Philips Research Labs, Netherlands.
    Operational Stability of Organic Field-Effect Transistors2012In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 24, no 9, p. 1146-1158Article in journal (Refereed)
    Abstract [en]

    Organic field-effect transistors (OFETs) are considered in technological applications for which low cost or mechanical flexibility are crucial factors. The environmental stability of the organic semiconductors used in OFETs has improved to a level that is now sufficient for commercialization. However, serious problems remain with the stability of OFETs under operation. The causes for this have remained elusive for many years. Surface potentiometry together with theoretical modeling provide new insights into the mechanisms limiting the operational stability. These indicate that redox reactions involving water are involved in an exchange of mobile charges in the semiconductor with protons in the gate dielectric. This mechanism elucidates the established key role of water and leads in a natural way to a universal stress function, describing the stretched exponential-like time dependence ubiquitously observed. Further study is needed to determine the generality of the mechanism and the role of other mechanisms.

  • 15.
    Charrier, D. S. H.
    et al.
    Eindhoven University of Technology, Netherlands.
    de Vries, T.
    Eindhoven University of Technology, Netherlands.
    Mathijssen, S. G. J.
    Eindhoven University of Technology, Netherlands; Philips Research Labs, Netherlands.
    Geluk, E. -J.
    Eindhoven University of Technology, Netherlands.
    Smits, E. C. P.
    Philips Research Labs, Netherlands; University of Groningen, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands.
    Bimolecular recombination in ambipolar organic field effect transistors2009In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 10, no 5, p. 994-997Article in journal (Refereed)
    Abstract [en]

    In ambipolar organic field effect transistors (OFET) the shape of the channel potential is intimately related to the recombination zone width W, and hence to the electron-hole recombination strength. Experimentally, the recombination profile can be assessed by scanning Kelvin probe microscopy (SKPM). However, surface potentials as measured by SKPM are distorted due to spurious capacitive couplings. Here, we present a (de)convolution method with an experimentally calibrated transfer function to reconstruct the actual surface potential from a measured SKPM response and vice versa. Using this scheme, we find W = 0.5 mu m for a nickel dithiolene OFET, which translates into a recombination rate that is two orders of magnitude below the value expected for Langevin recombination. (C) 2009 Elsevier B.V. All rights reserved.

  • 16.
    Charrier, Dimitri S. H.
    et al.
    Eindhoven University of Technology, Netherlands.
    Janssen, Rene A. J.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Large Electrically Induced Height and Volume Changes in Poly(3,4-ethylenedioxythiophene)/Poly(styrenesulfonate) Thin Films2010In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 22, no 12, p. 3670-3677Article in journal (Refereed)
    Abstract [en]

    We demonstrate large, partly reversible height and volume changes of thin films of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) on the anode of interdigitating gold electrodes under ambient conditions by applying an electrical bias. The height and volume changes were monitored with optical and atomic force microscopy and are found to be independent of initial film thickness. In the first cycle, a relative height change of 950% is observed for a 21 nm thick film. Two regimes are identified. In the first regime, reversible redox reactions occur and reversible height changes can be ascribed to absorption of water via osmotic effects, brought about by an increasing ion concentration on the anode. In the second, irreversible regime, irreversible overoxidation of the PEDOT occurs and mass transport from the channel to the anode becomes important.

  • 17.
    Charrier, Dimitri S. H.
    et al.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Smalbrugge, Barry E.
    Eindhoven University of Technology, Netherlands.
    de Vries, Tjibbe
    Eindhoven University of Technology, Netherlands.
    Janssen, Rene A. J.
    Eindhoven University of Technology, Netherlands.
    Real versus measured surface potentials in scanning Kelvin probe microscopy2008In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 2, no 4, p. 622-626Article in journal (Refereed)
    Abstract [en]

    Noncontact potentiometry or scanning Kelvin probe microscopy (SKPM) is a widely used technique to study charge injection and transport in (in)organic devices by measuring a laterally resolved local potential. This technique suffers from the significant drawback that experimentally obtained curves do not generally reflect the true potential profile in the device due to nonlocal coupling between the probing tip and the device. In this work, we quantitatively explain the experimental SKPM response and by doing so directly link theoretical device models to real observables. In particular, the model quantitatively explains the effects of the tip-sample distance and the dependence on the orientation of the probing tip with respect to the device.

  • 18.
    Chr Germs, W.
    et al.
    Eindhoven University of Technology, Netherlands.
    Guo, K.
    Eindhoven University of Technology, Netherlands.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Unusual Thermoelectric Behavior Indicating a Hopping to Bandlike Transport Transition in Pentacene2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 1, article id 016601Article in journal (Refereed)
    Abstract [en]

    An unusual increase in the Seebeck coefficient with increasing charge carrier density is observed in pentacene thin film transistors. This behavior is interpreted as being due to a transition from hopping transport in static localized states to bandlike transport, occurring at temperatures below similar to 250 K. Such a transition can be expected for organic materials in which both static energetic disorder and dynamic positional disorder are important. While clearly visible in the temperature and density dependent Seebeck coefficient, the transition hardly shows up in the charge carrier mobility.

  • 19.
    Chr Germs, W.
    et al.
    Eindhoven University of Technology, Netherlands.
    Roeling, E. M.
    Eindhoven University of Technology, Netherlands.
    van IJzendoorn, L. J.
    Eindhoven University of Technology, Netherlands.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Diffusion enhancement in on/off ratchets2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 7, article id 073104Article in journal (Refereed)
    Abstract [en]

    We show a diffusion enhancement of suspended polystyrene particles in an electrical on/off ratchet. The enhancement can be described by a simple master equation model. Furthermore, we find that the diffusion enhancement can be described by a general curve whose shape is only determined by the asymmetry of the ratchet repeat unit. The scaling of this curve can be explained from an analytical expression valid for small off-times. Finally, we demonstrate how the master equation model can be used to find the driving parameters for optimal particle separation. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793198]

  • 20.
    Chr Germs, Wijnand
    et al.
    Eindhoven University of Technology, Netherlands.
    Roeling, Erik M.
    [Germs, Netherlands.
    van IJzendoorn, Leo J.
    [Germs, Netherlands.
    Smalbrugge, Barry
    Eindhoven University of Technology, Netherlands.
    de Vries, Tjibbe
    Eindhoven University of Technology, Netherlands.
    Jan Geluk, Erik
    Eindhoven University of Technology, Netherlands.
    Janssen, Rene A. J.
    [Germs, Netherlands.
    Kemerink, Martijn
    [Germs, Netherlands.
    High-efficiency dielectrophoretic ratchet2012In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 86, no 4, article id 041106Article in journal (Refereed)
    Abstract [en]

    Brownian ratchets enable the use of thermal motion in performing useful work. They typically employ spatial asymmetry to rectify nondirected external forces that drive the system out of equilibrium (cf. running marbles on a shaking washboard). The major application foreseen for Brownian ratchets is high-selectivity fractionation of particle or molecule distributions. Here, we investigate the functioning of an important model system, the on/off ratchet forwater-suspended particles, in which interdigitated finger electrodes can be switched on and off to create a time-dependent, spatially periodic but asymmetric potential. Surprisingly, we find that mainly dielectrophoretic rather than electrophoretic forces are responsible for the ratchet effect. This has major implications for the (a) symmetry of the ratchet potential and the settings needed for optimal performance. We demonstrate that by applying a potential offset the ratchet can be optimized such that its particle displacement efficiency reaches the theoretical upper limit corresponding to the electrode geometry and particle size. Efficient fractionation based on size selectivity is therefore not only possible for charged species, but also for uncharged ones, which greatly expands the applicability range of this type of Brownian ratchet.

  • 21.
    Christian Roelofs, W. S.
    et al.
    Eindhoven University of Technology, Netherlands.
    Adriaans, Willem H.
    Eindhoven University of Technology, Netherlands.
    Janssen, Rene A. J.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    de Leeuw, Dago M.
    Max Planck Institute Polymer Research, Germany.
    Light Emission in the Unipolar Regime of Ambipolar Organic Field-Effect Transistors2013In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 23, no 33, p. 4133-4139Article in journal (Refereed)
    Abstract [en]

    Light emission from ambipolar organic field-effect transistors (OFETs) is often observed when they are operated in the unipolar regime. This is unexpected, the light emission should be completely suppressed, because in the unipolar regime only one type of charge carrier is accumulated. Here, an electroluminescent diketopyrrolopyrrole copolymer is investigated. Local potential measurements by scanning Kelvin probe microscopy reveal a recombination position that is unstable in time due to the presence of injection barriers. The electroluminescence and electrical transport have been numerically analyzed. It is shown that the counterintuitive unipolar light emission is quantitatively explained by injection of minority carriers into deep tail states of the semiconductor. The density of the injected minority carriers is small. Hence they are relatively immobile and they recombine close the contact with accumulated majority carriers. The unipolar light output is characterized by a constant efficiency independent of gate bias. It is argued that light emission from OFETs predominantly originates from the unipolar regime when the charge transport is injection limited.

  • 22.
    Christian Roelofs, W. S.
    et al.
    Eindhoven University of Technology, Netherlands; Philips Research Labs, Netherlands.
    Spijkman, Mark-Jan
    Philips Research Labs, Netherlands.
    Mathijssen, Simon G. J.
    Eindhoven University of Technology, Netherlands.
    Janssen, Rene A. J.
    Eindhoven University of Technology, Netherlands.
    de Leeuw, Dago M.
    Max Planck Institute Polymer Research, Germany; King Abdulaziz University, Saudi Arabia.
    Kemerink, Martijn
    Eindhoven University of Technology, MB, Eindhoven, The Netherlands.
    Fundamental Limitations for Electroluminescence in Organic Dual-Gate Field-Effect Transistors2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 26, p. 4450-+Article in journal (Refereed)
    Abstract [en]

    A dual-gate organic field-effect transistor is investigated for electrically pumped lasing. The two gates can independently accumulate electrons and holes, yielding current densities exceeding the lasing threshold. Here, the aim is to force the electrons and holes to recombine by confining the charges in a single semiconducting film. It is found that independent hole and electron accumulation is mutually exclusive with vertical recombination and light emission.

  • 23.
    Christova, C. G.
    et al.
    Eindhoven University of Technology, Netherlands.
    Stouwdam, J. W.
    Eindhoven University of Technology, Netherlands.
    Eijkemans, T. J.
    Eindhoven University of Technology, Netherlands.
    Silov, A. Yu.
    Eindhoven University of Technology, Netherlands.
    van der Heijden, R. W.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Salemink, H. W. M.
    Delft University of Technology, Netherlands.
    Photoluminescence enhancement in thin films of PbSe nanocrystals2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 12, article id 121906Article in journal (Refereed)
    Abstract [en]

    Remarkable photoluminescence enhancement (PLE) in submonolayer films of PbSe nanocrystals (NCs) upon continuous illumination was observed. The intensity increase from films on InP substrates was highest in vacuum, while for films on Si/SiO(2) substrates the PLE was stronger in air. The magnitude of the PLE was found to depend on the excitation intensity, being higher for a weaker irradiation power. The possible mechanisms behind the phenomenon of the PLE are discussed and it is suggested to originate mainly from charge trapping outside the NCs core. (C) 2008 American Institute of Physics.

  • 24.
    Cox, M.
    et al.
    Eindhoven University of Technology, Netherlands.
    Janssen, P.
    Eindhoven University of Technology, Netherlands.
    Wouters, S. H. W.
    Eindhoven University of Technology, Netherlands.
    van der Heijden, E. H. M.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands.
    The influence of device physics on organic magnetoresistance2013In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 173, p. 10-15Article in journal (Refereed)
    Abstract [en]

    In order to explain the surprisingly large, low field organic magnetoresistance (OMAR), several microscopic mechanisms have been proposed recently, but their effect on the polaron transport through a realistic device is relatively unknown. Here we study the effect of device physics on all proposed mechanisms, using a numerical drift-diffusion simulation method. We implement the local magnetic field dependent reactions via a magnetic field dependent recombination, mobility and triplet formation rate. Furthermore, a novel approach is used where we keep track of the subsequent particles formed from these reactions, including excitons and trions. We find that even in the most straightforward device structure sign changes can occur due to device physics. Especially the transition from a diffusion dominated to a drift dominated current near the built-in voltage plays a crucial role for understanding organic magnetoresistance. Finally, we conclude that the shape of the magnetocurrent as a function of voltage can be used as a fingerprint for the underlying dominant microscopic mechanism governing OMAR in a device. (c) 2012 Elsevier B.V. All rights reserved.

  • 25.
    Cox, M.
    et al.
    Eindhoven University of Technology, Netherlands.
    Wijnen, M. H. A.
    Eindhoven University of Technology, Netherlands.
    Wetzelaer, G. A. H.
    University of Groningen, Netherlands.
    Kemerink, Martijn
    Molecular Materials and Nanosystems, Eindhoven University of Technology, MB Eindhoven, The Netherlands.
    Blom, P. W. M.
    University of Groningen, Netherlands; Max Planck Institute Polymer Research, Germany.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands.
    Spectroscopic evidence for trap-dominated magnetic field effects in organic semiconductors2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 15, article id 155205Article in journal (Refereed)
    Abstract [en]

    Polaron traps are ubiquitous in organic semiconductors and recent evidence suggests they might be crucial for the large observed magnetic field effects (MFEs) in organic semiconductors. Here we measure MFEs in polymer thin-film devices with engineered, radiative trap sites in order to spectroscopically investigate the influence of the traps. Surprisingly, the luminescence at the trap sites and the polymer backbone is found to have an opposite response to a magnetic field. All our results are compatible with a mechanism in which spin mixing at the traps can create the large MFEs observed on the backbone. This scenario is quantitatively confirmed by numerical drift-diffusion modeling with magnetic-field-dependent exciton densities at the traps. These insights solve an outstanding controversy within the research field.

  • 26.
    Croitoru, MD
    et al.
    University of Antwerp, Netherlands.
    Gladilin, VN
    University of Antwerp, Netherlands.
    Fomin, VM
    University of Antwerp, Netherlands.
    Devreese, JT
    University of Antwerp, Netherlands.
    Kemerink, Martijn
    University of Antwerp, Netherlands.
    Koenraad, PM
    University of Antwerp, Netherlands.
    Sauthoff, K
    University of Antwerp, Netherlands.
    Wolter, JH
    University of Antwerp, Netherlands.
    Electroluminescence spectra of an STM-tip-induced quantum dot2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 19, article id 195307Article in journal (Refereed)
    Abstract [en]

    We analyze the electroluminescence spectrum of an STM-tip-induced quantum dot in a GaAs surface layer. A flexible model has been developed that combines analytical and numerical methods and describes the key features of many-particle states in the STM-tip-induced quantum dot. The dot is characterized by its depth and lateral width, which are experimentally controlled by the bias and current. We find, in agreement with experiment, that increasing the voltage on the STM tip results in a redshift of the electroluminescence peaks, while the peak positions as a function of electron tunneling current through the STM tip reveal a blueshift.

  • 27.
    Croitoru, MD
    et al.
    University of Instelling Antwerp, Netherlands.
    Gladilin, VN
    University of Instelling Antwerp, Netherlands.
    Fomin, VM
    University of Instelling Antwerp, Netherlands.
    Devreese, JT
    University of Instelling Antwerp, Netherlands.
    Kemerink, Martijn
    University of Instelling Antwerp, Netherlands.
    Koenraad, PM
    University of Instelling Antwerp, Netherlands.
    Sauthoff, K
    University of Instelling Antwerp, Netherlands.
    Wolter, JH
    University of Instelling Antwerp, Netherlands.
    Electroluminescence spectra of an STM-tip-induced quantum dot2004In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 21, no 2-4, p. 270-274Article in journal (Refereed)
    Abstract [en]

    We analyze the electroluminescence spectrum of an STM-tip-induced quantum dot in a GaAs surface layer. A flexible model has been developed, that combines analytical and numerical methods and describes the key features of many-particle states in the STM-tip-induced quantum dot. The dot is characterized by its depth and lateral width, which are experimentally controlled by the bias and the tunneling current. We find, in agreement with experiment, that increasing voltage on the STM-tip results in a red shift of the electroluminescence peaks, while the peak positions as a function of the electron tunneling current through the STM-tip reveal a blue shift. (C) 2003 Elsevier B.V. All rights reserved.

  • 28.
    Croitoru, MD
    et al.
    University of Antwerp, Moldova.
    Gladilin, VN
    University of Antwerp, Moldova.
    Fomin, VM
    University of Antwerp, Moldova.
    Devreese, JT
    University of Antwerp, Moldova.
    Kemerink, Martijn
    University of Antwerp, Moldova.
    Koenraad, PM
    University of Antwerp, Moldova.
    Sauthoff, K
    University of Antwerp, Moldova.
    Wolter, JH
    University of Antwerp, Moldova.
    Influence of the characteristics of the STM-tip on the electroluminescence spectra2005In: Physica. E, Low-Dimensional systems and nanostructures, ISSN 1386-9477, E-ISSN 1873-1759, Vol. 27, no 1-2, p. 13-20Article in journal (Refereed)
    Abstract [en]

    We analyze the influence of the characteristics of the STM-tip (applied voltage, tip radius) on the electroluminescence spectra from an STM-tip-induced quantum dot. We find that positions of electroluminescence peaks, attributed to the electron-hole recombination in the quantum dot, are very sensitive to the characteristics of the tip, namely increasing voltage on the STM-tip results in a red shift of the electroluminescence peaks, while the peak positions as a function of the tip radius reveal a non-monotonous behavior. (c) 2004 Elsevier B.V. All rights reserved.

  • 29.
    Di Nuzzo, Daniele
    et al.
    Technical University of Eindhoven, Netherlands.
    van Reenen, Stephan
    Technical University of Eindhoven, Netherlands.
    Janssen, Rene A. J.
    Technical University of Eindhoven, Netherlands.
    Kemerink, Martijn
    Technical University of Eindhoven, Netherlands.
    Meskers, Stefan C. J.
    Technical University of Eindhoven, Netherlands.
    Evidence for space-charge-limited conduction in organic photovoltaic cells at open-circuit conditions2013In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 8, article id 085207Article in journal (Refereed)
    Abstract [en]

    The ac admittance of solar cells under illumination is investigated under open-circuit conditions. Open-circuit conditions are imposed by inserting a probe capacitor into the circuit. The capacitance and conductance of the cells are investigated as function of frequency and continuous illumination intensity. Results are compared with numerical and analytical modeling of charge recombination and transport. In bulk heterojunction solar cells with [6,6]-Phenyl-C-61(C-71)-butyric acid methyl ester as acceptor and poly(3-hexylthiophene) or poly[2-methoxy-5-(2-ethylhexyloxy)-p-phenylene vinylene] as electron donor, the high-frequency capacitance C and conductance G follow a power-law dependence on intensity of white light I, with G(I) proportional to I-3/4 and C(I) proportional to I-1/4. The modeling shows that these dependencies can be explained in terms of space-charge-limited current in combination with Langevin type recombination of carriers. For poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b]dithiophene-2,6-diyl]] the capacitance shows a weaker dependence on intensity, indicating fast recombination of photogenerated carriers. Results indicate that the fill factor of relatively well performing polymer solar cells can still be limited by space charge effects and can be improved by enhancing the charge carrier mobility or by reducing the bimolecular Langevin recombination. DOI: 10.1103/PhysRevB.87.085207

  • 30.
    DInnocenzo, V.
    et al.
    Ist Italian Tecnol, Italy; Politecn Milan, Italy.
    Luzio, A.
    Ist Italian Tecnol, Italy.
    Abdalla, Hassan
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering. University of Groningen, Netherlands.
    Loi, M. A.
    University of Groningen, Netherlands.
    Natali, D.
    Ist Italian Tecnol, Italy; Politecn Milan, Italy.
    Petrozza, A.
    Ist Italian Tecnol, Italy.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Caironi, M.
    Ist Italian Tecnol, Italy.
    Two-dimensional charge transport in molecularly ordered polymer field-effect transistors2016In: JOURNAL OF MATERIALS CHEMISTRY C, ISSN 2050-7526, Vol. 4, no 47, p. 11135-11142Article in journal (Refereed)
    Abstract [en]

    Nanometer-thick Langmuir-Schafer monolayers of an electron transporting polymer display charge transport, optical and electro-optical properties that do not depend on the number of layers deposited one above the other. This phenomenon can be rationalized with the micro-structure of the specific multi-layers, which introduces an interlayer hopping penalty confining transport to a neat 2D regime, with a channel not extending beyond a single similar to 3 nm thick polymer strand, as confirmed by kinetic Monte Carlo simulations. Such findings are critical to establish a quantitative structure-property nexus in high mobility polymer semiconductors and in the control of charge transport at a molecular scale.

  • 31.
    Felekidis, Nikolaos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Stanford University, CA 94305 USA.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Design Rule for Improved Open-Circuit Voltage in Binary and Ternary Organic Solar Cells2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 42, p. 37070-37077Article in journal (Refereed)
    Abstract [en]

    Mixing different compounds to improve functionality is one of the pillars of the organic electronics field. Here, the degree to which the charge transport properties of the constituent materials are simply additive when materials are mixed is quantified. It is demonstrated that in bulk heterojunction organic solar cells, hole mobility in the donor phase depends critically on the choice of the acceptor material, which may alter the energetic disorder of the donor. The same holds for electron mobility and disorder in the acceptor. The associated mobility differences can exceed an order of magnitude compared to pristine materials. Quantifying these effects by a state-filling model for the open-circuit voltage (V-oc) of ternary Donor:Acceptor(l):Acceptor(2) (D:A(1):A(2)) organic solar cells leads to a physically transparent description of the surprising, nearly linear tunability of the Voc with the A(1):A(2) weight ratio. It is predicted that in binary OPV systems, suitably chosen donor and acceptor materials can improve the device power conversion efficiency (PCE) by several percentage points, for example from 11 to 13.5% for a hypothetical state-ofthe-art organic solar cell, highlighting the importance of this design rule.

    The full text will be freely available from 2018-10-02 11:48
  • 32.
    Felekidis, Nikolaos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Melianas, Armantas
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Nonequilibrium drift-diffusion model for organic semiconductor devices2016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 94, no 3, article id 035205Article in journal (Refereed)
    Abstract [en]

    Two prevailing formalisms are currently used to model charge transport in organic semiconductor devices. Drift-diffusion calculations, on the one hand, are time effective but assume local thermodynamic equilibrium, which is not always realistic. Kinetic Monte Carlo models, on the other hand, do not require this assumption but are computationally expensive. Here, we present a nonequilibrium drift-diffusion model that bridges this gap by fusing the established multiple trap and release formalism with the drift-diffusion transport equation. For a prototypical photovoltaic system the model is shown to quantitatively describe, with a single set of parameters, experiments probing (1) temperature-dependent steady-state charge transport-space-charge limited currents, and (2) time-resolved charge transport and relaxation of nonequilibrated photocreated charges. Moreover, the outputs of the developed kinetic drift-diffusion model are an order of magnitude, or more, faster to compute and in good agreement with kinetic Monte Carlo calculations.

  • 33.
    Felekidis, Nikolaos
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Wang, E.
    Chalmers University of Technology, Göteborg, Sweden.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, Netherlands.
    Open circuit voltage and efficiency in ternary organic photovoltaic blends2016In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 1, p. 257-266Article in journal (Refereed)
    Abstract [en]

    Organic bulk heterojunction solar cells based on ternary blends of two donor absorbers and one acceptor are investigated by experiments and modeling. The commonly observed continuous tunability of the open circuit voltage V-OC with the donor1 : donor2 ratio can quantitatively be explained as quasi-Fermi level splitting due to photocreated charges filling a joint density of states that is broadened by Gaussian disorder. On this basis, a predictive model for the power conversion efficiency that accounts for the composition-dependent absorption and the shape of the current-voltage characteristic curve is developed. When all other parameters, most notably the fill factor, are constant, we find that for state-of-the-art absorbers, having a broad and strong absorption spectrum, ternary blends offer no advantage over binary ones. For absorbers with a more narrow absorption spectrum ternary blends of donors with complementary absorption spectra, offer modest improvements over binary ones. In contrast, when, upon blending, transport and/or recombination kinetics are improved, leading to an increased fill factor, ternaries may offer significant advantages over binaries.

  • 34.
    Fitie, Carel F. C.
    et al.
    Eindhoven University of Technology, Netherlands.
    Christian Roelofs, W. S.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Sijbesma, Rint P.
    Eindhoven University of Technology, Netherlands.
    Remnant Polarization in Thin Films from a Columnar Liquid Crystal2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 20, p. 6892-+Article in journal (Refereed)
    Abstract [en]

    Ferroelectric switching is demonstrated in a hydrogen bonded columnar liquid crystalline (LC) material. Polar order induced in the LC phase can be frozen by crystallization of the alkyl chains in the periphery of the columns yielding thin films with remnant polarization and an unprecedented high surface potential as shown by scanning Kelvin probe microscopy.

  • 35.
    Fitie, Carel F. C.
    et al.
    Eindhoven University of Technology, Netherlands.
    Christian Roelofs, W. S.
    Eindhoven University of Technology, Netherlands.
    Magusin, Pieter C. M. M.
    Eindhoven University of Technology, Netherlands.
    Wubbenhorst, Michael
    Katholieke University of Leuven, Belgium.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Sijbesma, Rint P.
    Eindhoven University of Technology, Netherlands.
    Polar Switching in Trialkylbenzene-1,3,5-tricarboxamides2012In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 13, p. 3928-3937Article in journal (Refereed)
    Abstract [en]

    The hydrogen-bonded hexagonal columnar LC (Col(hd)) phases formed by benzene-1,3,5-tricarboxamide (BTA) derivatives can be aligned uniformly by an electric field and display switching behavior with a high remnant polarization. The polar switching in three symmetrically substituted BTAs with alkyl chains varying in length between 6 and 18 carbon atoms (C6, C10, and C18) was investigated by electro-optical switching experiments, dielectric relaxation spectroscopy (DRS), and solid-state NMR The goal was to characterize ferroelectric properties of BTA-based columnar LCs, which display a macroscopic axial dipole moment due to the head-to-tail stacking of hydrogen-bonded amides. The Col(hd) phase of all three BTAs can be aligned uniformly by a dc field similar to 30 V/mu m. Moreover, C10 and C18 display extrinsic polar switching characterized by a remnant polarization and coercive field of 1-2 mu C/cm(2) and 20-30 V/mu m, respectively. In the absence of an external field, the polarization is lost in 1-1000 s, depending on device details and temperature. DRS revealed a columnar glass transition in the low-temperature region of the LC phase related to collective vibrations in the hydrogen-bonded columns that freeze out below 41-54 degrees C. At higher temperatures, a relaxation process is present originating from the collective reorientation of amide groups along the column axis (inversion of the macrodipole). Matching activation energies suggest that the molecular mechanism underlying the polar switching and the R-processes is identical. These results illustrate that LC phases based on BTAs offer the unique possibility to integrate polarization with other functionalities in a single nanostructured material.

  • 36.
    Garcia-Iglesias, Miguel
    et al.
    Eindhoven University of Technology, Netherlands.
    de Waal, Bas F. M.
    Eindhoven University of Technology, Netherlands.
    Gorbunov, Andrey V.
    Eindhoven University of Technology, Netherlands.
    Palmans, Anja R. A.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, Netherlands.
    Meijer, E. W.
    Eindhoven University of Technology, Netherlands.
    A Versatile Method for the Preparation of Ferroelectric Supramolecular Materials via Radical End-Functionalization of Vinylidene Fluoride Oligomers2016In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, no 19, p. 6217-6223Article in journal (Refereed)
    Abstract [en]

    A synthetic method for the end-functionalization of vinylidene fluoride oligomers (OVDF) via a radical reaction between terminal olefins and I-OVDF is described. The method shows a wide substrate scope and excellent conversions, and permits the preparation of different disc-shaped cores such as benzene-1,3,5-tricarboxamides (BTAs), perylenes bisimide and phthalocyanines (Pc) bearing three to eight ferroelectric oligomers at their periphery. The formation, purity, OVDF conformation, and morphology of the final adducts has been assessed by a combination of techniques, such as NMR, size exclusion chromatography, differential scanning calorimetry, polarized optical microscopy, and atomic force microscopy. Finally, PBI-OVDF and Pc-OVDF materials show ferroelectric hysteresis behavior together with high remnant polarizations, with values as high as P-r approximate to 37 mC/m(2) for Pc-OVDF. This work demonstrates the potential of preparing a new set of ferroelectric materials simply by attaching OVDF oligomers to different small molecules. The use of carefully chosen small molecules paves the way to new functional materials in which ferroelectricity and electrical conductivity or light-harvesting properties coexist in a single compound.

  • 37.
    Germs, W. Chr.
    et al.
    Eindhoven University of Technology, Netherlands.
    Adriaans, W. H.
    Eindhoven University of Technology, Netherlands.
    Tripathi, A. K.
    TNO, Netherlands.
    Roelofs, W. S. C.
    Eindhoven University of Technology, Netherlands.
    Cobb, B.
    TNO, Netherlands.
    Janssen, R. A. J.
    TNO, Netherlands.
    Gelinck, G. H.
    TNO, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Charge transport in amorphous InGaZnO thin-film transistors2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 15, article id 155319Article in journal (Refereed)
    Abstract [en]

    We investigate the mechanism of charge transport in indium gallium zinc oxide (a-IGZO), an amorphous metal-oxide semiconductor. We measured the field-effect mobility and the Seebeck coefficient (S = Delta V/Delta T) of a-IGZO in thin-film transistors as a function of charge-carrier density for different temperatures. Using these transistors, we further employed a scanning Kelvin probe-based technique to determine the density of states of a-IGZO that is used as the basis for the modeling. After comparing two commonly used models, the band transport percolation model and a mobility edge model, we find that both cannot describe the full properties of the charge transport in the a-IGZO semiconductor. We, therefore, propose a model that extends the mobility edge model to allow for variable range hopping below the mobility edge. The extended mobility edge model gives a superior description of the experimental results. We show that the charge transport is dominated by variable range hopping below, rather than by bandlike transport above the mobility edge.

  • 38.
    Gholamrezaie, Fatemeh
    et al.
    University of Groningen, Netherlands; Philips Research Labs, Netherlands.
    Andringa, Anne-Marije
    University of Groningen, Netherlands; Philips Research Labs, Netherlands.
    Christian Roelofs, W. S.
    Philips Research Labs, Netherlands; Eindhoven University of Technology, Netherlands.
    Neuhold, Alfred
    Graz University of Technology, Austria.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Blom, Paul W. M.
    University of Groningen, Netherlands; Holst Centre TNO, Netherlands.
    de Leeuw, Dago M.
    University of Groningen, Netherlands; Philips Research Labs, Netherlands.
    Charge Trapping by Self-Assembled Monolayers as the Origin of the Threshold Voltage Shift in Organic Field-Effect Transistors2012In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 8, no 2, p. 241-245Article in journal (Refereed)
    Abstract [en]

    The threshold voltage is an important property of organic field-effect transistors. By applying a self-assembled monolayer (SAM) on the gate dielectric, the value can be tuned. After electrical characterization, the semiconductor is delaminated. The surface potentials of the revealed SAM perfectly agree with the threshold voltages, which demonstrate that the shift is not due to the dipolar contribution, but due to charge trapping by the SAM.

  • 39.
    Gommans, HHP
    et al.
    Eindhoven University of Technology, Germany.
    Kemerink, Martijn
    Eindhoven University of Technology, Germany.
    Andersson, GG
    Eindhoven University of Technology, Germany.
    Pijper, RMT
    Eindhoven University of Technology, Germany.
    Charge transport and trapping in Cs-doped poly(dialkoxy-p-phenylene vinylene) light-emitting diodes2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 15, article id 155216Article in journal (Refereed)
    Abstract [en]

    Al/Cs/MDMO-PPV/ITO (where MDMO-PPV stands for poly[2-methoxy-5-(3()-7()-dimethyloctyloxy)-1,4phenylene vinylene] and ITO is indium tin oxide) light-emitting diode (LED) structures, made by physical vapor deposition of Cs on the emissive polymer layer, have been characterized by electroluminescence, current-voltage, and admittance spectroscopy. Deposition of Cs is found to improve the balance between electron and hole currents, enhancing the external electroluminescence efficiency from 0.01 cd A(-1) for the bare Al cathode to a maximum of 1.3 cd A(-1) for a Cs coverage of only 1.5x10(14) atoms/cm(2). By combining I-V and admittance spectra with model calculations, in which Cs diffusion profiles are explicitly taken into account, this effect could be attributed to a potential drop at the cathode interface due to a Cs-induced electron donor level 0.61 eV below the lowest unoccupied molecular orbital. In addition, the admittance spectra in the hole-dominated regime are shown to result from space-charge-limited conduction combined with charge relaxation in trap levels. This description allows us to directly determine the carrier mobility, even in the presence of traps. In contrast to recent literature, we demonstrate that there is no need to include dispersive transport in the description of the carrier mobility to explain the excess capacitance that is typically observed in admittance spectra of pi-conjugated materials.

  • 40.
    Gommans, HHP
    et al.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Janssen, RAJ
    Eindhoven University of Technology, Netherlands.
    Negative capacitances in low-mobility solids2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 23, article id 235204Article in journal (Refereed)
    Abstract [en]

    The negative capacitance as often observed at low frequencies in semiconducting devices is explained by bipolar injection in diode configuration. Numerical calculations are performed within the drift-diffusion approximation in the presence of bimolecular recombination of arbitrary strength. Scaling relations for the characteristic frequency with bias, sample dimensions, and carrier mobilities are presented in the limits of weak and strong recombination. Finally, impedance measurements conducted on a light-emitting diode and photovoltaic cell based on low-mobility organic semiconductors are modeled as a function of bias and temperature, respectively.

  • 41.
    Gommans, HHP
    et al.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Kramer, JM
    Eindhoven University of Technology, Netherlands.
    Janssen, RAJ
    Eindhoven University of Technology, Netherlands.
    Field and temperature dependence of the photocurrent in polymer/fullerene bulk heterojunction solar cells2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 12, article id 122104Article in journal (Refereed)
    Abstract [en]

    The photocurrent in polymer/fullerene blends is characterized as a function of bias at temperatures ranging from 125 to 300 K. Assuming a constant generation rate and bimolecular recombination, the results are numerically modeled within the drift-diffusion approximation. Bimolecular recombination is found to be a dominant factor in the field dependence of the photocurrent in the entire measured voltage range. Inclusion of field dependent geminate pair dissociation and recombination via the Onsager expressions gives a much stronger field dependence than experimentally observed. From the temperature dependence of the extracted mobilities, we can simultaneously estimate the broadening of the transporting highest occupied and lowest unoccupied molecular orbital levels. (c) 2005 American Institute of Physics.

  • 42.
    Gommans, HHP
    et al.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Schilders, WHA
    Eindhoven University of Technology, Netherlands.
    Universality of ac conduction for generalized space-charge transport in ordered solids2005In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 16, article id 165110Article in journal (Refereed)
    Abstract [en]

    On numerous nonmetallic systems, the ac conductivity is observed to follow an approximate power law behavior sigma(omega)=omega(s) with 0 amp;lt; s amp;lt;= 1. We show that the presence of nonlimiting, i.e., ohmic, contacts on the sample necessarily leads to these characteristics. The ac conductivity curves are obtained by the numerical solution of the complete set of time-dependent drift-diffusion equations. The calculated ac conductivity curves can be converted into quasiuniversal master curves by application of the Taylor-Isard scaling law for an arbitrary temperature dependence of the mobility. Our results demonstrate that space-charge transport can lead to the commonly observed power law and scaling behaviors without incorporating disorder. Nevertheless, the implications of disorder are discussed and they are expected to increase the range over which the power law behavior extends.

  • 43.
    Gorbunov, A. V.
    et al.
    Eindhoven University of Technology, Netherlands.
    Putzeys, T.
    Katholieke University of Leuven, Belgium.
    Urbanaviciute, Indre
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands.
    Wubbenhorst, M.
    Katholieke University of Leuven, Belgium.
    Sijbesma, R. P.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, Netherlands.
    True ferroelectric switching in thin films of trialkylbenzene-1,3,5-tricarboxamide (BTA)2016In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 34, p. 23663-23672Article in journal (Refereed)
    Abstract [en]

    We have investigated the ferroelectric polarization switching properties of trialkylbenzene-1,3,5-tricarboxamide (BTA), which is a model system for a large class of novel organic ferroelectric materials. In the solid state BTAs form a liquid crystalline columnar hexagonal phase that provides long range order that was previously shown to give rise to hysteretic dipolar switching. In this work the nature of the polar switching process is investigated by a combination of dielectric relaxation spectroscopy, depth-resolved pyroelectric response measurements, and classical frequency- and time-dependent electrical switching. We show that BTAs, when brought in a homeotropically aligned hexagonal liquid crystalline phase, are truly ferroelectric. Analysis of the transient switching behavior suggests that the ferroelectric switching is limited by a highly dispersive nucleation process, giving rise to a wide distribution of switching times.

  • 44.
    Gorbunov, Andrey V.
    et al.
    Eindhoven University of Technology, Netherlands.
    Haedler, Andreas T.
    Eindhoven University of Technology, Netherlands.
    Putzeys, Tristan
    Katholieke University of Leuven, Belgium.
    Zha, R. Helen
    Eindhoven University of Technology, Netherlands.
    Schmidt, Hans-Werner
    University of Bayreuth, Germany.
    Kivala, Milan
    University of Erlangen Nurnberg, Germany.
    Urbanaviciute, Indre
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Wubbenhorst, Michael
    Katholieke University of Leuven, Belgium.
    Meijer, E. W.
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, Netherlands.
    Switchable Charge Injection Barrier in an Organic Supramolecular Semiconductor2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 24, p. 15535-15542Article in journal (Refereed)
    Abstract [en]

    We disclose a supramolecular material that combines semiconducting and dipolar functionalities. The material consists of a discotic semiconducting carbonyl-bridged triarylamine core, which is surrounded by three dipolar amide groups. In thin films, the material self-organizes in a hexagonal columnar fashion through Jr-stacking of the molecular core and hydrogen bonding between the amide groups. Alignment by an electrical field in a simple metal/semiconductor/metal geometry induces a polar order in the interface layers near the metal contacts that can be reversibly switched, while the bulk material remains nonpolarized. On suitably chosen electrodes, the presence of an interfacial polarization field leads to a modulation of the barrier for charge injection into the semiconductor. Consequently, a reversible switching is possible between a high-resistance, injection-limited off-state and a low-resistance, space-charge-limited on-state. The resulting memory diode shows switchable rectification with on/off ratios of up to two orders of magnitude. This demonstrated multifunctionality of a single material is a promising concept toward possible application in lowcost, large-area, nonvolatile organic memories.

  • 45.
    Gorbunov, Andrey V.
    et al.
    Eindhoven Univ Technol, Netherlands.
    Iglesias, Miguel Garcia
    Eindhoven Univ Technol, Netherlands.
    Guilleme, Julia
    Univ Autonoma Madrid, Spain.
    Cornelissen, Tim
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Roelofs, W. S. Christian
    Eindhoven Univ Technol, Netherlands.
    Torres, Tomas
    Univ Autonoma Madrid, Spain; IM DEA Nanociencia, Spain.
    Gonzalez-Rodriguez, David
    Univ Autonoma Madrid, Spain.
    Meijer, E. W.
    Eindhoven Univ Technol, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven Univ Technol, Netherlands.
    Ferroelectric self-assembled molecular materials showing both rectifying and switchable conductivity2017In: Science Advances, ISSN 0036-8156, E-ISSN 2375-2548, Vol. 3, no 9, article id e1701017Article in journal (Refereed)
    Abstract [en]

    Advanced molecular materials that combine two or more physical properties are typically constructed by combining different molecules, each being responsible for one of the properties required. Ideally, single molecules could take care of this combined functionality, provided they are self-assembled correctly and endowed with different functional subunits whose strong electronic coupling may lead to the emergence of unprecedented and exciting properties. We present a class of disc-like semiconducting organic molecules that are functionalized with strong dipolar side groups. Supramolecular organization of these materials provides long-range polar order that supports collective ferroelectric behavior of the side groups as well as charge transport through the stacked semiconducting cores. The ferroelectric polarization in these supramolecular polymers is found to couple to the charge transport and leads to a bulk conductivity that is both switchable and rectifying. An intuitive model is developed and found to quantitatively reproduce the experimental observations. In a larger perspective, these results highlight the possibility of modulating material properties using the large electric fields associated with ferroelectric polarization.

  • 46.
    Gorbunov, A.V.
    et al.
    Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven, Netherlands.
    Iglesias, M.G.
    Institute of Complex Molecular Systems, Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.
    Guilleme, J.
    Departamento de Química Orgá-nica (C-I), Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
    Cornelissen, Tim
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Roelofs, W.S.C.
    Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven, Netherlands.
    Torres, T.
    Departamento de Química Orgá-nica (C-I), Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain; IM-DEA Nanociencia, c/ Faraday 9, Madrid, Spain.
    González-Rodríguez, D.
    Departamento de Química Orgá-nica (C-I), Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain.
    Meijer, E.W.
    Institute of Complex Molecular Systems, Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, Eindhoven, Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, Eindhoven, Netherlands.
    Ferroelectric self-assembled molecular materials showing both rectifying and switchable conductivity2017In: Science Advances, ISSN 0036-8156, E-ISSN 2375-2548, Vol. 3, no 9, article id e1701017Article in journal (Refereed)
    Abstract [en]

    Advanced molecular materials that combine two or more physical properties are typically constructed by combining different molecules, each being responsible for one of the properties required. Ideally, single molecules could take care of this combined functionality, provided they are self-assembled correctly and endowed with different functional subunits whose strong electronic coupling may lead to the emergence of unprecedented and exciting properties. We present a class of disc-like semiconducting organic molecules that are functionalized with strong dipolar side groups. Supramolecular organization of these materials provides long-range polar order that supports collective ferroelectric behavior of the side groups as well as charge transport through the stacked semiconducting cores. The ferroelectric polarization in these supramolecular polymers is found to couple to the charge transport and leads to a bulk conductivity that is both switchable and rectifying. An intuitive model is developed and found to quantitatively reproduce the experimental observations. In a larger perspective, these results highlight the possibility of modulating material properties using the large electric fields associated with ferroelectric polarization.

  • 47.
    Gorbunov, AV
    et al.
    Eindhoven University of Technology, the Netherlands.
    Meng, X
    Eindhoven University of Technology, the Netherlands.
    Urbanaviciute, Indre
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering.
    Putzeys, T
    KU Leuven, Heverlee, Belgium.
    Wübbenhorst, M
    KU Leuven, Heverlee, Belgium.
    Sijbesma, RP
    Eindhoven University of Technology, the Netherlands.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Complex Materials and Devices. Linköping University, Faculty of Science & Engineering. Eindhoven University of Technology, the Netherlands.
    Polarization loss in the organic ferroelectrictrialkylbenzene-1,3,5-tricarboxamide (BTA)2017In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 19, no 4, p. 3192-3200Article in journal (Refereed)
    Abstract [en]

    We investigate the polarization loss in the archetypical molecular organic ferroelectric trialkylbenzene-1,3,5-tricarboxamide (BTA). We prove that the polarization loss is due to thermally activated R-relaxation,which is a collective reversal of the amide dipole moments in ferroelectric domains. By applying a weakelectrostatic field both the polarization loss and the R-relaxation are suppressed, leading to anenhancement of the retention time by at least several orders of magnitude. Alternative loss mechanismsare discussed and ruled out. By operating the thin-film devices slightly above the crystalline to liquidcrystalline phase transition temperature the retention time of one compound becomes more than12 hours even in absence of supportive bias, which is among the longest reported so far for organicferroelectric materials.

  • 48.
    Hallam, Toby
    et al.
    University of Cambridge, England.
    Lee, MiJung
    University of Cambridge, England.
    Zhao, Ni
    University of Cambridge, England.
    Nandhakumar, Iris
    University of Southampton, England.
    Kemerink, Martijn
    University of Cambridge, England; Eindhoven University of Technology, Netherlands.
    Heeney, Martin
    University of London Imperial Coll Science Technology and Med, England.
    McCulloch, Iain
    University of London Imperial Coll Science Technology and Med, England.
    Sirringhaus, Henning
    University of Cambridge, England.
    Local Charge Trapping in Conjugated Polymers Resolved by Scanning Kelvin Probe Microscopy2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 25, article id 256803Article in journal (Refereed)
    Abstract [en]

    The microstructure of conjugated polymers is heterogeneous on the length scale of individual polymer chains, but little is known about how this affects their electronic properties. Here we use scanning Kelvin probe microscopy with resolution-enhancing carbon nanotube tips to study charge transport on a 100 nm scale in a chain-extended, semicrystalline conjugated polymer. We show that the disordered grain boundaries between crystalline domains constitute preferential charge trapping sites and lead to variations on a 100 nm scale of the carrier concentration under accumulation conditions.

  • 49.
    Haverkort, JEM
    et al.
    Eindhoven University of Technology, Netherlands.
    Dorren, BHP
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Silov, AY
    Eindhoven University of Technology, Netherlands.
    Wolter, JH
    Eindhoven University of Technology, Netherlands.
    Design of a polarization independent SOA at 1.55 mu m using composite InAsP/InGaAs quantum wells.1999In: ECIO99: 9TH EUROPEAN CONFERENCE ON INTEGRATED OPTICS AND TECHNICAL EXHIBITION, IST INT COMUNICAZIONI , 1999, p. 483-486Conference paper (Refereed)
    Abstract [en]

    We aim to extend the polarization independent SOA reported by Tiemeijer(1) to 1550 nm. Conventional quantum wells (QW) do not allow TM-gain at 1550 nm without exceeding the critical layer thickness. Composite InAsP/InGaAs QWs show high TM-differential gain at 1550 nm while simultaneously providing strain compensation.

  • 50.
    Haverkort, JEM
    et al.
    Eindhoven University of Technology, Netherlands.
    Dorren, BHP
    Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands.
    Silov, AY
    Eindhoven University of Technology, Netherlands.
    Wolter, JH
    Eindhoven University of Technology, Netherlands.
    Design of composite InAsP/InGaAs quantum wells for a 1.55 mu m polarization independent semiconductor optical amplifier1999In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 75, no 18, p. 2782-2784Article in journal (Refereed)
    Abstract [en]

    We investigate a composite InAsP/InGaAs quantum well in which an 8 nm tensile strained InGaAs well is surrounded by two compressively strained InAsP layers which feature a 70:30 conduction band offset ratio. The composite quantum well is found to provide a high TM differential gain. The InAsP layers provide strain compensation while simultaneously shifting the band gap to the relevant 1.55 mu m wavelength region and increasing the electron confinement. Composite InAsP/InGaAs quantum wells are a promising candidate for realizing a polarization independent semiconductor optical amplifier at 1.55 mu m. (C) 1999 American Institute of Physics. [S0003-6951(99)01944-0].

1234 1 - 50 of 170
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf