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  • 1.
    Du, Chun-Xia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Duteil, F.
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Efficient 1.54 µm light emission from Si/SiGe/Si: Er2001In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 81, no 1-3, p. 105-108Article in journal (Refereed)
    Abstract [en]

    Si/SiGe/Si:Er:O-heterojunction bipolar transistor (HBT)-type light emitting devices with Er3+ ions incorporated in the collector region have been fabricated using layered structures prepared by differential molecular beam epitaxy (MBE). Intense light emission at 1.54 µm has been observed at room temperature by hot electron impact excitation at rather low injection current and applied voltage. Separate controls of the injection current and bias voltage make it possible to perform detailed electroluminescence (EL) studies that can not be done with conventional Si:Er light emitting diodes (LEDs). Saturation of the EL intensity occurs at very low current densities indicating a 100-fold increase of the effective excitation cross-section for Si/SiGe/Si:Er:O-HBTs compared with Si:Er-LEDs. © 2001 Elsevier Science B.V.

  • 2.
    Du, Chun-Xia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Duteil, F.
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Si/SiGe/Si: Er2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 12, p. 1697-1699Article in journal (Refereed)
    Abstract [en]

    Si/SiGe/Si:Er:O heterojunction bipolar transistor (HBT) type light-emitting devices with Er3+ ions incorporated in the collector region have been fabricated using a layered structure grown by differential molecular-beam epitaxy. Electroluminescence measurements on processed light-emitting HBTs can be performed in either constant driving current mode or constant applied bias mode, which is an important advantage over conventional Si:Er light-emitting diodes. Intense room-temperature light emission at the Er3+ characteristic wavelength of 1.54 µm has been observed at low driving current density, e.g., 0.1 A cm-2, and low applied bias, e.g., 3 V, across the collector and emitter. © 2001 American Institute of Physics.

  • 3.
    Du, Chun-Xia
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Duteil, Fabrice
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hansson, Göran
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Si/SiGe/Si : Er : O light-emitting transistors prepared by differential molecular-beam epitaxy2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 12, p. 1697-1699Article in journal (Refereed)
    Abstract [en]

    Si/SiGe/Si:Er:O heterojunction bipolar transistor (HBT) type light-emitting devices with Er3+ ions incorporated in the collector region have been fabricated using a layered structure grown by differential molecular-beam epitaxy. Electroluminescence measurements on processed light-emitting HBTs can be performed in either constant driving current mode or constant applied bias mode, which is an important advantage over conventional Si:Er light-emitting diodes. Intense room-temperature light emission at the Er3+ characteristic wavelength of 1.54 mum has been observed at low driving current density, e.g., 0.1 A cm(-2), and low applied bias, e.g., 3 V, across the collector and emitter. (C) 2001 American Institute of Physics.

  • 4.
    Du, Chun-Xia
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Joelsson, KB
    Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Duteil, F
    Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Electroluminescence studies of Er and SiO co-doped Si layers prepared by molecular beam epitaxy2000In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 14, no 3, p. 259-265Article in journal (Refereed)
    Abstract [en]

    Er/O co-doped Si light emitting diodes (LEDs) have been fabricated using layer structures prepared by molecular beam epitaxy (MBE). The Er/O doping was realized by sublimation of elemental Er and silicon monoxide simultaneously with Si during MBE growth. Intense Er-related electroluminescence (EL) at 1.54 mu m was observed at room temperature from p(+)-SiGe/i-SiGe-Si/Si:Er/n(+)-Si LEDs by electron impact excitation under reverse bias. It has been found that the EL intensity was increased with increasing growth temperature of the Si:Er/O layer in the range of 430-575 degrees C. The electrical pumping power dependence of EL intensity has been studied. An excitation cross section value of similar to 1 x 10(-16) cm(2) was estimated based on the experimental data and model fitting. The EL decay behavior under various injection and bias conditions has been studied by time-resolved EL measurements. The overall luminescence decay time is found to strongly depend on the injection parameters. Two types of de-excitation mechanisms due to Auger energy transfer to free carriers introduced by either dopant ionization or carrier injection have been discussed. Both Auger processes play an important role in reduction of the EL intensity when there is a high density of carriers with excited Er ions. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 5. Duteil, F.
    et al.
    Du, Chun-Xia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Jarrendahl, K.
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Er/O doped Si1-xGex alloy layers grown by MBE2001In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 17, no 1-2, p. 131-134Conference paper (Other academic)
    Abstract [en]

    Silicon-based light emitting diodes (LEDs) containing an Er/O-doped Si1-xGex active layer have been studied. The structures were grown by molecular beam epitaxy (MBE), with Er and O concentrations of 5 × 1019 and 1 × 1020 cm-3, respectively, using Er and silicon monoxide sources. The microstructure has been studied by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy, and it is found that Er/O-doped Si0.92Ge0.08 layers of high crystalline quality, can be obtained. Electroluminescence (EL) measurements have been performed on reverse-biased Er/O doped diodes both from the surface and from the edge and the emission at 1.54 µm associated with the Er3+ ions has been studied at 300 K and lower temperatures. To evaluate the possibility to use a Si1-xGex layer for waveguiding in Si-based optoelectronics, studies of the refractive index n of strained Si1-xGex as a function of the Ge concentration have been done by spectroscopic ellipsometry in the range 0.3-1.7 µm. At 1.54 µm the refractive index increases monotonically with the Ge concentration up to n = 3.542 for a Ge concentration of 21.3%. © 2001 Elsevier Science B.V.

  • 6. Duteil, F.
    et al.
    Du, Chun-Xia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Joelsson, K.B.
    Persson, Per
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Luminescence and microstructure of Er/O co-doped Si structures grown by MBE using Er and SiO evaporation2000In: Materials Science in Semiconductor Processing, ISSN 1369-8001, E-ISSN 1873-4081, Vol. 3, no 5-6, p. 523-528Article in journal (Refereed)
    Abstract [en]

    Er and O co-doped Si structures have been prepared using molecular-beam epitaxy (MBE) with fluxes of Er and O obtained from Er and silicon monoxide (SiO) evaporation in high-temperature cells. The incorporation of Er and O has been studied for concentrations of up to 2×1020 and 1×1021 cm-3, respectively. Surface segregation of Er can take place, but with O co-doping the segregation is suppressed and Er-doped layers without any indication of surface segregation can be prepared. Si1-xGex and Si1-yCy layers doped with Er/O during growth at different substrate temperatures show more defects than corresponding Si layers. Strong emission at 1.54µm associated with the intra-4f transition of Er3+ ions is observed in electroluminescence (EL) at room temperature in reverse-biased p-i-n-junctions. To optimize the EL intensity we have varied the Er/O ratio and the temperature during growth of the Er/O-doped layer. Using an Er-concentration of around 1×1020 cm-3 we find that Er/O ratios of 1:2 or 1:4 give higher intensity than 1:1 while the stability with respect to breakdown is reduced for the highest used O concentrations. For increasing growth temperatures in the range 400-575 °C there is an increase in the EL intensity. A positive effect of post-annealing on the photoluminescence intensity has also been observed.

  • 7.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Pettitt, Michala E
    University of Birmingham.
    Conlan, Sheelagh L
    Newcastle University.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Callow, Maureen E
    University of Birmingham.
    Callow, James A
    University of Birmingham.
    Mutton, Robert
    Newcastle University.
    Clare, Anthony S
    Newcastle University.
    D`Souza, Fraddry
    TNO Science and Industry.
    Donnelly, Glen
    TNO Science and Industry.
    Bruin, Anouk
    TNO Science and Industry.
    Willemsen, Peter R
    TNO Science and Industry.
    Su, Xueju J
    University of Dundee.
    Wang, Su
    University of Dundee.
    Zhao, Qi
    University of Dundee.
    Hederos, Markus
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Resistance of Galactoside-Terminated Alkanethiol Self-Assembled Monolayers to Marine Fouling Organisms2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 10, p. 3890-3901Article in journal (Refereed)
    Abstract [en]

    Self-assembled monolayers (SAMs) of galactoside-terminated alkanethiols have protein-resistance properties which can be tuned via the degree of methylation [Langmuir 2005, 21, 2971-2980]. Specifically, a partially methylated compound was more resistant to nonspecific protein adsorption than the hydroxylated or fully methylated counterparts. We investigate whether this also holds true for resistance to the attachment and adhesion of a range of marine species, in order to clarify to what extent resistance to protein adsorption correlates with the more complex adhesion of fouling organisms. The partially methylated galactoside-terminated SAM was further compared to a mixed monolayer of omega-substituted methyl- and hydroxyl-terminated alkanethiols with wetting properties and surface ratio of hydroxyl to methyl groups matching that of the galactoside. The settlement (initial attachment) and adhesion strength of four model marine fouling organisms were investigated, representing both micro- and macrofoulers; two bacteria (Cobetia marina and Marinobacter hydrocarbonoclasticus), barnacle cypris larvae (Balanus amphitrite), and algal zoospores (Ulva linza). The minimum in protein adsorption onto the partially methylated galactoside surface was partly reproduced in the marine fouling assays, providing some support for a relationship between protein resistance and adhesion of marine fouling organisms. The mixed alkanethiol SAM, which was matched in wettability to the partially methylated galactoside SAM, consistently showed higher settlement (initial attachment) of test organisms than the galactoside, implying that both wettability and surface chemistry are insufficient to explain differences in fouling resistance. We suggest that differences in the structure of interfacial water may explain the variation in adhesion to these SAMs.

  • 8.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Nygren, Patrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Pettitt, M. E.
    University of Birmingham.
    Oumlstblom, M.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Broo, Klas
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Callow, M. E.
    University of Birmingham.
    Callow, J.
    University of Birmingham.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Anomalous settlement behavior of Ulva linza zoospores on cationic oligopeptide surfaces2008In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 24, no 4, p. 303-312Article in journal (Refereed)
    Abstract [en]

    Identification of settlement cues for marine fouling organisms opens up new strategies and methods for biofouling prevention, and enables the development of more effective antifouling materials. To this end, the settlement behaviour of zoospores of the green alga Ulva linza onto cationic oligopeptide self-assembled monolayers (SAMs) has been investigated. The spores interact strongly with lysine- and arginine-rich SAMs, and their settlement appears to be stimulated by these surfaces. Of particular interest is an arginine-rich oligopeptide, which is effective in attracting spores to the surface, but in a way which leaves a large fraction of the settled spores attached to the surface in an anomalous fashion. These 'pseudo-settled' spores are relatively easily detached from the surface and do not undergo the full range of cellular responses associated with normal commitment to settlement. This is a hitherto undocumented mode of settlement, and surface dilution of the arginine-rich peptide with a neutral triglycine peptide demonstrates that both normal and anomalous settlement is proportional to the surface density of the arginine-rich peptide. The settlement experiments are complemented with physical studies of the oligopeptide SAMs, before and after extended immersion in artificial seawater, using infrared spectroscopy, null ellipsometry and contact angle measurements.

  • 9.
    Ederth, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Pettitt, M E
    University of Birmingham.
    Nygren, Patrik
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Ekblad, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Zhou, Ye
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Falk, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Physics. Linköping University, Faculty of Science & Engineering.
    Callow, M E
    University of Birmingham.
    Callow, J A
    University of Birmingham.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Interactions of Zoospores of Ulva linza with Arginine-Rich Oligopeptide Monolayers2009In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, no 16, p. 9375-9383Article in journal (Refereed)
    Abstract [en]

    We recently reported oil the strong interactions of zoospores of the green alga, Ulva linza with all arginine-rich oligopeptide self-assembled monolayer (SAM) [Biofouling 2008, 24, 303-312], where the arginine-rich peptide induced not only high spore settlement, but also a form of abnormal settlement, or "pseudo-settlement", whereby it proportion of spores do not go through the normal process of surface exploration, adhesive exocytosis, and loss of flagella. Further. it was demonstrated that both the total number of settled spores and the fraction of pseudosettled spores were related to the surface density of the arginine-rich peptide. Here we present a further investigation of the interactions of zoospores of ulva with a set of oligomeric, de nom designed, arginine-rich peptides, specifically aimed to test the effect of peptide primary structure on the interaction. Via variations in the peptide length and by permutations in the amino acid sequences, we gain further insight into the spore-surface interactions. The interpretation of the biological assays is supported by physicochemical characterization of the SAMs using infrared spectroscopy, ellipsometry, and contact angle measurement. Results confirm the importance of arginine residues for the anomalous pseudosettlement, and we found that settlement is modulated by variations in both the total length and peptide primary structure. To elucidate the Causes of the anomalous settlement and the possible relation to peptide-membrane interactions, we also compared the settlement of the "naked" zoospores of Ulva(which present it lipoprotein membrane to the exterior without a discrete polysaccharide cell wall), with the settlement of diatoms (unicellular algae that are surrounded by it silica cell wall), onto the peptide SAMs. Cationic SAMs do not notably affect settlement (attachment), adhesion strength, or viability of diatom cells, Suggesting that the effect of the peptides on zoospores of Ulva is mediated via specific peptide-membrane interactions.

  • 10.
    Hansson, Göran
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Ni, Wei-Xin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Du, Chun-Xia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Elfving, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Duteil, F.
    Origin of abnormal temperature dependence of electroluminescence from Er/O-doped Si diodes2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 78, no 15, p. 2104-2106Article in journal (Refereed)
    Abstract [en]

    The temperature dependencies of the current-voltage characteristics and the electroluminescence (EL) intensity of molecular beam epitaxy grown Er/O-doped Si light emitting diodes at reverse bias have been studied. To minimize the scattering of electrons injected from the p-doped Si1-xGex electron emitters, an intrinsic Si layer was used in the depletion region. For many diodes, there is a temperature range where the EL intensity increases with temperature. Data are reported for a structure that shows increasing intensity up to 100°C. This is attributed to an increasing fraction of the pumping current being due to phonon-assisted tunneling, which gives a higher saturation intensity, compared to ionization-dominated breakdown at lower temperatures. © 2001 American Institute of Physics.

  • 11.
    Karim, Amir
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hansson , Göran
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics . Linköping University, The Institute of Technology.
    Influence of exposure to 980 nm laser radiation on the luminescence of Si: Er/O light-emitting diodes2008In: JOURNAL OF APPLIED PHYSICS, ISSN 0021-8979 , Vol. 104, no 12, p. 123110-Article in journal (Refereed)
    Abstract [en]

    Erbium (Er) codoping with oxygen (O) in Si is a well-known method for producing electroluminescent material radiating at 1.54 mu m through a 4f shell transition of Er3+ ions. In this work the influence of exposure to 980 nm radiation on the electroluminescence (EL) of reverse biased Si:Er/O light-emitting diodes (LEDs), which give a strong room temperature 1.54 mu m intensity, is presented and discussed. All the device layers, including Er/O doped Si sandwiched between two Si0.82Ge0.18 layers, have been grown on silicon on insulator substrates using molecular beam epitaxy and processed to fabricate edge emitting Si:Er/O waveguide LEDs. Electromagnetic mode confinement simulations have been performed to optimize the layer parameters for waveguiding. The temperature dependence of the 1.54 mu m EL intensity exhibits an abnormal temperature quenching with a peak near -30 degrees C, and at -160 degrees C it has decreased by a factor of 5. However, irradiating the devices with a 980 nm laser gives an enhancement of the 1.54 mu m EL intensity, which is more dramatic at low temperatures (e.g., -200 degrees C) where the quenched EL signal is increased up to almost the same level as at room temperature. The enhancement of the EL intensity is attributed to the photocurrent generated by the 980 nm laser, reducing the detrimental avalanche current.

  • 12.
    Larsson (Kaiser), Andréas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Du, Chun-Xia
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    Liedberg, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics. Linköping University, The Institute of Technology.
    UV-patterned poly(ethylene glycol) matrix for microarray applications2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 11, p. 3511-3518Article in journal (Refereed)
    Abstract [en]

    A versatile method to fabricate polymeric matrixes for microarray applications is demonstrated. Several different design strategies are presented where a variety of organic films, such as plastic polymers and self-assembled monolayers (SAMs) on planar silica and gold substrates, act as supports for the graft polymerization procedure. An ensemble of poly(ethylene glycol) methacrylate monomers are combined to obtain a matrix with desired properties:  low nonspecific binding and easily accessible groups for postimmobilization of ligands. The free radical graft polymerization process occurs under irradiation with UV light in the 254−266 nm range, which offers the possibility to introduce patterns by means of a photomask. The arrays are created on inert and homogeneous coatings prepared either by graft polymerization of a methoxy-terminated PEG−methacrylate or self-assembly of a methoxy-terminated oligo(ethylene glycol) thiol. Carboxylic acid groups, introduced in the array spots either during graft polymerization or upon wet chemical conversion of hydroxyls, grant the capability to immobilize proteins and other molecules via free amine groups. Immobilization of fluorescent species as well as biotin followed by exposure to a fluorescently labeled antibody directed toward biotin display both excellent integrity of the spots and low nonspecific binding to the surrounding framework. Beside patterns of uniform height and size, an array of spots with varying thickness (a sort of gradient) is demonstrated. Such gradient samples enable us to address critical issues regarding the mechanism(s) behind spatially resolved free radical polymerization of methacrylates. It also offers a convenient route to optimize the matrix properties with respect to thickness, loading capacity, protein diffusion/penetration, and nonspecific binding.

  • 13.
    Ni, Wei-Xin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Du, Chun-Xia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Duteil, F.
    Elfving, Anders
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    1.54 µm light emitting devices based on Er/O-doped Si layered structures grown by molecular beam epitaxy2001In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 17, no 1-2, p. 65-69Conference paper (Other academic)
    Abstract [en]

    Two types of Si:Er light emitting devices have been processed and characterized with an aim to efficiently use hot electrons for impact excitation. One is a p+-SiGe/i-Si/n-Si:Er:O/n+-Si tunneling diode with a design favoring electron tunneling from the SiGe valence band to the Si conduction band and subsequent acceleration. Another type of Si:Er light emitters is based on a heterojunction bipolar transistor (HBT) structure containing an Er-doped active layer in the collector. In these devices, one can introduce hot electrons from the HBT emitter in a controlled way with a collector bias voltage prior to the avalanche breakdown to improve the impact excitation efficiency. Intense electroluminescence was observed at 300 K at low current (0.1 A cm-2) and low bias (3 V). An impact cross-section value of 1 × 10-14 cm2 has been estimated, which is a 100-fold increase compared with the values reported from any other type of Er-doped LEDs. © 2001 Elsevier Science B.V.

  • 14.
    Ni, Wei-Xin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Du, Chun-Xia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Duteil, F.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hansson, Göran
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Light emitting SiGe/i-Si/Si: Er2000In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 369, no 1, p. 414-418Article in journal (Refereed)
    Abstract [en]

    p+-SiGe/i-Si/n-Si:Er:O/n+-Si tunneling diodes have been processed using layer structures prepared by molecular beam epitaxy (MBE). Electroluminescence has been observed at room temperature from these devices at reverse bias. The devices have been used for characterizing the optical activation of Er3+ ions in MBE Si:Er:O layers grown at different conditions. In the range of 400-575 °C, a high substrate temperature is favored for formation of Er emission centers, but this is limited by the silicidation process occurring above 600 °C. Several important device parameters such as the impact excitation cross section and various EL decay processes have been carefully studied. A fast decay (approximately 4 µs) due to the Auger carrier transfer process is observed.

  • 15.
    Zhou, Yi
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Du, Chunxia
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ni, Wei-Xin
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Andersson, Mats R
    Chalmers, Dept Chem & Biol Engn.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend Systems by Photoluminescence and Electroluminescence Studies2009In: ADVANCED FUNCTIONAL MATERIALS, ISSN 1616-301X, Vol. 19, no 20, p. 3293-3299Article in journal (Refereed)
    Abstract [en]

    The presence of charge transfer states generated by the interaction between the fullerene acceptor PCBM and two alternating copolymers of fluorene with donor-acceptor-donor comonomers are reported; the generation leads to modifications in the polymer bandgap and electronic structure. In one of polymer/fullerene blends, the driving; force for photocurrent generation, i.e., the gap between the lowest unoccupied molecular orbitals of the donor and acceptor, is only 0.1 eV, but photocurrent is generated. It is shown that the presence of a charge transfer state is more important than the driving force. The charge transfer states are visible through new emission peaks in the photoluminescence spectra and through electroluminescence at a forward bias. The photoluminescence can be quenched under reverse bias, and can be directly correlated to the mechanism of photocurrent generation. The excited charge transfer state is easily dissociated into free charge carriers, and is an important intermediate state through which free charge carriers are generated.

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