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  • 1.
    Bolin, Maria
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Svennersten, Karl
    Karolinska Institute.
    Wang, Xiangjun
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Chronakis, Ioannis S
    Industrial Research & Development Corporation.
    Richter-Dahlfors, Agneta
    Karolinska Institute.
    Jager, Edwin
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nano-fiber scaffold electrodes based on PEDOT for cell stimulation2009In: SENSORS AND ACTUATORS B-CHEMICAL, ISSN 0925-4005, Vol. 142, no 2, p. 451-456Article in journal (Refereed)
    Abstract [en]

    Electronically conductive and electrochemically active 3D-scaffolds based on electrospun poly(ethylene terephthalate) (PET) nano-fibers are reported. Vapour phase polymerization was employed to achieve an uniform and conformal coating of poly(3,4-ethylenedioxythiophene) doped with tosylate (PEDOT:tosylate) on the nano-fibers. The PEDOT coatings had a large impact on the wettability, turning the hydrophobic PET fibers super-hydrophilic. SH-SY5Y neuroblastoma cells were grown on the PEDOT coated fibers. The SH-SY5Y cells adhered well and showed healthy morphology. These electrically active scaffolds were used to induce Ca2+ signalling in SH-SY5Y neuroblastoma cells. PEDOT:tosylate coated nano-fibers represent a class of 3D host environments that combines excellent adhesion and proliferation for neuronal cells with the possibility to regulate their signalling.

  • 2.
    Buyanova, Irina A
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, W M
    University of California.
    Tu, C W
    University of California.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Effects of Ga doping on optical and structural properties of ZnO epilayers2009In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 45, no 4-5, p. 413-420Article in journal (Refereed)
    Abstract [en]

    Effects of Ga incorporation on electrical, structural and optical properties of ZnO epilayers are systematically studied by employing structural and optical characterization techniques combined with electrical and secondary ion mass spectrometry measurements. A non-monotonous dependence of free electron concentrations on Ga content is observed and is attributed to defect formation and phase separation. The former process is found to dominate for Ga concentrations of around 2-3x1020 cm-3. corresponding defects are suggested to be responsible for a broad red emission, which peaks at around 1.8 eV at K. Characteristic properties of this emission are well accounted for by assuming intracenter transitions at a deep center, of which the associated Huang-Rhys factor and mean phonon energy are determined. For higher Ga doping levels, the phase separation is found to be significant. It is that under these conditions only a minor fraction of incorporated Ga atoms form shallow donors, which leads to the observed dramatic decrease of carrier concentration.

  • 3.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Izadifard, M.
    Department of Physics, Shahrood University of Technology, Shahrood, Iran.
    Norton, D.P.
    Department of Materials Science and Engineering, University of Florida, Gainesville, FL, USA.
    Pearton, S.J.
    Department of Materials Science and Engineering, University of Florida, Gainesville, FL, USA.
    Osinsky, A.
    SVT Associates, Eden Prairie, MN, USA.
    Dong, J.W.
    SVT Associates, Eden Prairie, MN, USA.
    Dabiran, A.
    SVT Associates, Eden Prairie, MN, USA.
    Optical characterization of Zn(1-x)Cd(x)O alloys grown by molecular-beam epitaxy2006In: 210th ECS Meeting Volume 3, Issue 5: State-of-the-Art Program on Compound Semiconductors 45 (SOTAPOCS 45) -and- Wide Bandgap Semiconductor Materials and Devices 7 / [ed] F. Ren, J. Bardwell, P. Chang, W. Johnson, P. Shen, E. Stokes, The Electrochemical Society , 2006, Vol. 3, p. 391-398Conference paper (Other academic)
    Abstract [en]

    We have carried out comprehensive optical studies to evaluate structural and bandgap properties of Zn1-xCdxO alloys with x{less than or equalto}0.17 grown by molecular beam epitaxy. High crystalline quality ofthe alloys was concluded from cathodoluminescence measurements. Based on absorptionand reflectance measurements, the compositional dependence of the bandgap energyof ZnCdO, estimated without taking into account excitonic effects, wasfound to follow the trend Eg(x)=3.28-2.23x+0.45x2. Degradation in the alloyquality due to possible phase separation was found to causedeviations from this trend, evident from a more rapid redshift of the absorption edge. Effects of Cd incorporation onthe variation of the bandgap energies with temperature are alsodiscussed.

  • 4.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pozina, G.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Lim, W.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Norton, D. P.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Pearton, S. J.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Osinsky, A.
    SVT Associates Eden Prairie, Minnesota 55344, USA.
    Dong, J. W.
    SVT Associates Eden Prairie, Minnesota 55344, USA.
    Hertog, B.
    SVT Associates Eden Prairie, Minnesota 55344, USA.
    Effects of hydrogen on the optical properties of ZnCdO/ZnO quantum wells grown by molecular beam epitaxy2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, p. 261912-Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent cw- and time-resolved photoluminescence (PL), as well as optically detected magnetic resonance (ODMR) measurements are employed to evaluate effects of deuterium (2H) doping on optical properties of ZnCdO/ZnO quantum well structures grown by molecular beam epitaxy. It is shown that incorporation of 2H from a remote plasma causes a substantial improvement in radiative efficiency of the investigated structures. Based on transient PL measurements, the observed improvements are attributed to efficient passivation by hydrogen of competing nonradiative recombination centers via defects. This conclusion is confirmed from the ODMR studies.

  • 5.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Utsumi, A.
    Furukawa, Y.
    Wakahara, A.
    Yonezu, H.
    Formation of grown-in defects in molecular beam epitaxial Ga(In)NP: effects of growth conditions and post-growth treatments2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, p. 063519-Article in journal (Refereed)
    Abstract [en]

    Effects of growth conditions and post-growth treatments, such as presence of N ions, N2 flow, growth temperature, In alloying, and postgrowth rapid thermal annealing (RTA), on formation of grown-in defects in Ga(In)NP prepared by molecular beam epitaxy are studied in detail by the optically detected magnetic resonance (ODMR) technique. Several common residual defects, such as two Ga-interstitial defects (i.e., Gai-A and Gai-B) and two unidentified defects with a g factor around 2 (denoted by S1 and S2), are closely monitored. Bombardment of impinging N ions on grown sample surface is found to facilitate formation of these defects. Higher N2 flow is shown to have an even more profound effect than a higher number of ions in introducing these defects. Incorporation of a small amount of In (e.g., 5.1%) in GaNP seems to play a minor role in the formation of the defects. In GaInNP with 45% of In; however, the defects were found to be abundant. Effect of RTA on the defects is found to depend on initial configurations of Gai-related defects formed during the growth. In the alloys where the Gai-A and Gai-B defects are absent in the as-grown samples (i.e., GaNP grown at a low temperature of 460 °C), the concentrations of the two Gai defects are found to increase after postgrowth RTA. This indicates that the defects originally introduced in the as-grown alloys have been transformed into the more thermally stable Gai-A and Gai-B during RTA. On the other hand, when the Gai-A and Gai-B are readily abundant (e.g., at higher growth temperatures (>=500 °C), RTA leads to a slight reduction of the Gai-A and Gai-B ODMR signals. The S2 defect is also shown to be thermally stable upon the RTA treatment.

  • 6.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Vorona, I. P
    Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine.
    Vlasenko, L. S.
    A. F. Ioffe Physico-Technical Institute, St. Petersburg, Russia.
    Wang, X. J.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Utsumi, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Furukawa, Y.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Wakahara, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Buyanova, I. A.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Chen, W. M.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Evidence for a phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, p. 115334-Article in journal (Refereed)
    Abstract [en]

    Optically detected magnetic resonance (ODMR) studies of molecular beam epitaxial GaNP/GaP structures reveal presence of a P-related complex defect, evident from its resolved hyperfine interaction between an unpaired electronic spin (S=1/2) and a nuclear spin (I = ½) of a 31P atom. The principal axis of the defect is concluded to be along a <111> crystallographic direction from angular dependence of the ODMR spectrum, restricting the P atom (either a PGa antisite or a Pi interstitial) and its partner in the complex defect to be oriented along this direction. The principal values of the electronic g-tensor and hyperfine interaction tensor are determined as: g=2.013, g=2.002, and A=130´10-4 cm-1, A=330´10-4 cm-1, respectively. The interface nature of the defect is clearly manifested by the absence of the ODMR lines originating from two out of four equivalent <111> orientations. Defect formation is shown to be facilitated by nitrogen ion bombardment under non-equilibrium growth conditions and the defect is thermally stable upon post-growth thermal annealing.

  • 7.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Vorona, Igor P
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Vlasenko, Leonid S
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Utsumi, A
    University of Technology, Toyohashi, Aichi, Japan.
    Furukawa, Y
    University of Technology, Toyohashi, Aichi, Japan.
    Wakahara, A
    University of Technology, Toyohashi, Aichi, Japan.
    Yonezu, H
    University of Technology, Toyohashi, Aichi, Japan.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Phosphorus-related interfacial defect complex at a GaP/GaNP heterojunction2010Conference paper (Other academic)
    Abstract [en]

    For full exploration of dilute nitrides in device applications, a better understanding and control of defects located at interfaces involving e.g. Ga(In)NP are required. In this work we report on the first identification of a point defect situated at an interface between two semiconductors: GaNP and GaP. The defect is concluded to be a complex involving a P antisite or a P interstitial in its core, partnered with a neighboring impurity/defect aligned along a <111> direction, from detailed angular dependence studies of the optically detected magnetic resonance (ODMR) spectra at both X- and Q-band microwave frequencies. The principal g and A values, g=2.013, g=2.002, A=130x10-4 cm-1 and A=330x10-4 cm-1, are obtained from a spin Hamiltonian analysis. The interface nature of the defect is clearly evident from the absence of the ODMR lines originating from two out of four equivalent <111> orientations. Defect formation is shown to be facilitated by severe nitrogen ion bombardment under non-equilibrium growth conditions during solid-source molecular beam epitaxy and the defect is thermally stable upon post-growth thermal annealing.

  • 8.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Wang, X
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Geelhaar, L.
    Infineon Technologies, Corporate Research, Munich, Germany .
    Riechert, H.
    Infineon Technologies, Corporate Research, Munich, Germany .
    Optically detected cyclotron resonance studies of InGaNAs/GaAs structures2007In: Physics of semiconductors : 28th International Conference on the Physics of Semiconductors, ICPS 2006, Vienna, Austria, 24-28 July 2006, American Institute of Physics (AIP), 2007, p. 383-384Conference paper (Other academic)
    Abstract [en]

    We report on our recent results from a systematic study of layered structures containing an InGaNAs/GaAs quantum well (QW), by the optically detected cyclotron resonance (ODCR) technique. By monitoring photoluminescence (PL) emissions from various layers the predominant ODCR peak is shown to be related to carriers with a 2D character and an effective mass of 0.51 me. The responsible carriers are ascribed to be electrons in GaAs/AlAs superlattices (SL) that are employed in the laser structures to prevent carrier leak by sandwiching the InGaNAs/GaAs QW. This conclusion is based on the following observations: (a) the ODCR peak is only observed in the structures containing the SL; (b) the effective mass value determined by the ODCR peak is independent of In and N compositions; (c) the same ODCR peak is also observed by monitoring PL from the SL. Unfortunately no ODCR signal related to InGaNAs was observed

  • 9.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Geelhaar, L.
    Riechert, H.
    Optically detected cyclotron resonance studies of InxGa1-xNyAs1-y/GaAs quantum wells sandwiched between type-II AlAs/GaAs superlattices.2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, p. 073705-Article in journal (Refereed)
    Abstract [en]

      We report on our results from a systematic study of layered structures containing an InGaNAs/GaAs single quantum well (SQW) enclosed between staggered type II AlAs/GaAs superlattices (SL), by the photoluminescence (PL) and optically detected cyclotron resonance (ODCR) techniques. Besides the ODCR signal known to originate from electrons in GaAs, the predominant ODCR peak is shown to be related to carriers with a two-dimensional character and a cyclotron resonance effective mass of m*[approximate](0.51-0.56)m0. The responsible carriers are ascribed to electrons on the ellipsoidal equienergy surface at the AlAs X point of the Brillouin zone within the SL, based on results from angular and spectral dependences of the ODCR signal. No ODCR signal related to the InGaNAs SQW was detected, presumably due to low carrier mobility despite the high optical quality. Multiple absorption of photons with energy below the band gap energy of the SL and the GaAs barriers was observed, which bears implication on the efficiency of light-emitting devices based on these structures.

  • 10.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Polimeni, A.
    INFM and Dipartimento di Fisica,Università di Roma “La Sapienza”, Piazzale A. Moro 2, I-00185 Roma, Italy.
    Capizzi, M.
    INFM and Dipartimento di Fisica,Università di Roma “La Sapienza”, Piazzale A. Moro 2, I-00185 Roma, Italy.
    Buyanova, I. A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Activation of defects in GaNP by post-growth hydrogen treatmentManuscript (preprint) (Other academic)
    Abstract [en]

    Effect of post-growth hydrogen treatment on defects and their role in carrier recombination in molecular beam epitaxial GaNP alloys is examined by means of photoluminescence and optically detected magnetic resonance. We present direct experimental evidence for effective activation of several different defects in carrier recombination by the hydrogen treatment. Among them, two defect complexes are identified to contain a Ga interstitial (Gai). None of the activated Gai complexes was previously observed in GaNP. Possible mechanisms for the hydrogen-induced defect activation are discussed.

  • 11.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Utsumi, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Furukawa, Y.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Wakahara, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Effect of growth conditions on grown-in defect formation and luminescence efficiency in GaInNP epilayers grown by molecular-beam epitaxy.2008In: Physica status solidi (c)Special Issue: E-MRS 2007 Spring Meeting – Symposium F and Conference on Photonic Materials, Weinheim: Wiley-VCH Verlagsgesellschaft, 2008, Vol. 5, p. 460-463Conference paper (Refereed)
    Abstract [en]

    A detailed study of the impact of different growth conditions (i.e. ion bombardment, nitrogen flow and In content) on the defect formation in Ga(In)NP epilayers grown on GaP substrates by solid-source molecular beam epitaxy is performed. Reduced nitrogen ion bombardment during the growth is shown to significantly reduce formation of defects acting as competing recombination centers, such as a Ga interstitial defect and other unidentified defects revealed by optically detected magnetic resonance. Further, high nitrogen flow is found to be even more effective than the ion bombardment in introducing the defects. The incorporation of In by 5.1% is, on the other hand, found not to affect the introduction of defects. The results provide a useful insight into the formation mechanism of the defects that will hopefully shed light on a control of the defect introduction in the alloys by optimizing growth conditions.

  • 12.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C W
    University of California San Diego.
    Polimeni, A
    University Roma La Sapienza.
    Capizzi, M
    University Roma La Sapienza.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Effect of postgrowth hydrogen treatment on defects in GaNP2011In: APPLIED PHYSICS LETTERS, ISSN 0003-6951, Vol. 98, no 14, p. 141920-Article in journal (Refereed)
    Abstract [en]

    Effect of postgrowth hydrogen treatment on defects and their role in carrier recombination in GaNP alloys is examined by photoluminescence (PL) and optically detected magnetic resonance. We present direct experimental evidence for effective activation of several defects by low-energy subthreshold hydrogen treatment (andlt;= 100 eV H ions). Among them, two defect complexes are identified to contain a Ga interstitial. Possible mechanisms for the H-induced defect activation and creation are discussed. Carrier recombination via these defects is shown to efficiently compete with the near band-edge PL, explaining the observed degraded optical quality of the alloys after the H treatment.

  • 13.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C.W.
    University of California.
    Polimeni, A.
    University Roma La Sapienza.
    Capizzi, M.
    University Roma La Sapienza.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Activation of defects in GaNP by low-energy hydrogen treatment2011In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, 2011, p. PC3.36-Conference paper (Other academic)
  • 14.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Utsumi, A.
    Furukawa, Y.
    Moon, S.
    Wakahara, A.
    Yonezu, H.
    Critical issue of defects in Ga(In)NP alloys: a new and promising material system for integration of III-V-based optoelectronics with Si-based microelectronics.2007In: 31th Workshop on Compound Semiconductor Devices and Integrated Circuits WOCSDICE 2007,2007, 2007, p. 149-151Conference paper (Other academic)
  • 15.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Utsumi, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Furukawa, Y.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Moon, S.
    Wakahara, A.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Yonezu, H.
    Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
    Effect of growth conditions on grown-in defects in Ga(In)NP alloys2007Conference paper (Other academic)
  • 16.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Vorona, Igor
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Utsumi, A.
    Furukawa, Y.
    Moon, S.
    Wakahara, A.
    Yonezu, H.
    Spin resonance spectroscopy of grown-in defects in Ga(In)NP alloys2008In: 7th International Conference on Physics of Light-Matter Coupling in Nanostructures, 2007, Elsevier Ltd. , 2008, p. 620-625Conference paper (Refereed)
    Abstract [en]

    We employ the optically detected magnetic resonance (ODMR) technique to study and identify important grown-in defects in Ga(In)NP grown by molecular-beam epitaxy (MBE). Several types of defects were revealed from ODMR studies. The dominant defects were found to be related to Ga interstitials, evident form their characteristic hyperfine interaction arising from the spin interaction between the electron and the Ga nucleus. Some other as yet unidentified intrinsic defects were also found to be commonly present in the alloys. The effects of growth conditions (ion bombardment, N2 gas flow, etc.) and post-growth rapid thermal annealing on the formation of these defects were studied in detail, shedding light on the formation mechanism of defects.

  • 17.
    Gadisa, Abay
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Wang, Xiangjun
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Admassie, Shimelis
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Perzon, Erik
    Department of Organic Chemistry and Polymer Technology, Chalmers University of Technology, Göteborg, Sweden.
    Oswald, Frédéric
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Toledo, Spain.
    Langa, Fernando
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Toledo, Spain.
    Andersson, Mats R.
    Department of Organic Chemistry and Polymer Technology, Chalmers University of Technology, Göteborg, Sweden.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Stoichiometry dependence of charge transport in polymer/methanofullerene and polymer/C70 derivative based solar cells2006In: Organic electronics, ISSN 1566-1199, Vol. 7, no 4, p. 195-204Article in journal (Refereed)
    Abstract [en]

    Charge transport in a near infrared absorbing polyfluorene copolymer (APFO-Green1) and its blends with methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and 3′-(3,5-bis-trifluoromethylphenyl)-1′-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) is reported. PCBM and BTPF70 are electron acceptor and transporting molecules in polymer based solar cells. The BTPF70 has emerged as a new electron acceptor molecule that provides adequate exciton dissociation when blended with the low band gap polyfluorene copolymer APFO-Green1. Electron transport in both net PCBM and BTPF70 films are subjected to positional and energetic disorder, with the degree of disorder being more pronounced in BTPF70. On the other hand, mixing PCBM with conjugated polymers usually leads to increased hole mobility. We have investigated and compared the acceptor concentration dependence of charge transport in APFO-Green1/PCBM and APFO-Green1/BTPF70 blend films. For better understanding of the charge transport in the heterojunction films, the field and temperature dependence of hole transport in pure APFO-Green1 films has also been studied. It is observed that the behavior of hole mobility in the blend layer is sensitive to the acceptor type. For APFO-Green1/PCBM hole only devices, the hole mobility attains a local maximum at 67 wt.% of PCBM, while on the contrary mixing any amount of BTPF70 with APFO-Green1 results into degradation of hole transport. Electron transport in both blends, however, increases monotonically as a function of acceptor loading.

  • 18.
    Gadisa, Abay
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Perzon, Erik
    Chalmers Tekniska högskola.
    Oswald, Frederic
    Universidad de castilla-La Mancha.
    Langa, F
    Universidad de Castilla -la mancha.
    Andersson, M R
    Chalmers Tekniska Högskola.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Effect of acceptor type on hole transport in polymer/acceptor bulk heterojunction films2006In: European Conference on Hybrid and Organic Cells, ECHOS 06,2006, 2006Conference paper (Other academic)
  • 19.
    Inganäs, Olle
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Svensson, M.
    Materials and Surface Chemistry, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Zhang, Fengling
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Gadisa, Abay
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Persson, Nils-Krister
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, M.R.
    Materials and Surface Chemistry, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Low bandgap alternating polyfluorene copolymers in plastic photodiodes and solar cells2004In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 79, no 1, p. 31-35Article in journal (Refereed)
    Abstract [en]

    We report a comparative study of plastic photodiodes using four different copolymers of fluorene, with a variation of alkyl side chain length and chemical structure. Photodiode materials are formed by blending the polymers with a fullerene derivative and spincoating the blend solution. A photovoltage of 1 V is obtained in devices, where the anode is a doped polymer and the cathode is LiF/Al. Monochromatic quantum efficiencies are better than 40% over most of the absorption range, and under solar light AM 1.5 simulation, we reach energy efficiencies beyond 2%. The high fill factors obtained in some of the devices indicate that these are of interest for more elaborate optimisation. Reasons for the benign electrical transport are discussed. © Springer-Verlag 2004.

  • 20.
    Inganäs, Olle
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Zhang, Fengling
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Gadisa, Abay
    IPS/ÌFM Linköpings universitet.
    Persson, Nils-Krister
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Svensson, Mattias
    Chalmers Tekniska Högskola.
    Perzon, Erik
    Chalmers Tekniska Högskola.
    Mammo, W
    Chalmers Tekniska Högskola.
    Andersson, M.R.
    Chalmers Tekniska Högskola.
    Alternating fluorene copolymer/fullerene blend solar cells2005In: Organic Photovoltaics: Mechanisms, Materials and Devices / [ed] Sam-Shajing Sun, Niyazi Serdar Sariciftci, Boca Raton, FL, USA: CRC Press , 2005, 1, p. 387-402Chapter in book (Other academic)
    Abstract [en]

    Recently developed organic photovoltaics (OPVs) show distinct advantages over their inorganic counterparts due to their lighter weight, flexible shape, versatile materials synthesis and device fabrication schemes, and low cost in large-scale industrial production. Although many books currently exist on general concepts of PV and inorganic PV materials and devices, few are available that offer a comprehensive overview of recently fast developing organic and polymeric PV materials and devices.

    Organic Photovoltaics: Mechanisms, Materials, and Devicesfills this gap. The book provides an international perspective on the latest research in this rapidly expanding field with contributions from top experts around the world.  It presents a unified approach comprising three sections: General Overviews; Mechanisms and Modeling; and Materials and Devices. Discussions include sunlight capture, exciton diffusion and dissociation, interface properties, charge recombination and migration, and a variety of currently developing OPV materials/devices. The book also includes two forewords: one by Nobel Laureate Dr. Alan J. Heeger, and the other by Drs. Aloysius Hepp and Sheila Bailey of NASA Glenn Research Center.

    Organic Photovoltaics equips students, researchers, and engineers with knowledge of the mechanisms, materials, devices, and applications of OPVs necessary to develop cheaper, lighter, and cleaner renewable energy throughout the coming decades.

  • 21.
    Jager, Edwin
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Bolin, Maria
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Svennersten, Karl
    Karolinska Insitutet, Inst. för Neurovetenskap.
    Wang, X
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Richter-Dahlfors, Agneta
    Karolinska Insitutet, Inst. för Neurovetenskap.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Electroactive Surfaces Based on Conducting Polymers for Controlling Cell Adhesion, Signaling, and Proliferation2009In: Transducers 2009: The 15th International Conferece on solid-State Sensors, Actuators & Microsystems, IEEE conference proceedings, 2009, p. 1778-1781Conference paper (Other academic)
    Abstract [en]

    We report on a variety of electroactive surfaces for the control of in vitro cell adhesion, proliferation, and stimulation. Planar cell culture substrates have been coated with the conducting polymer PEDOT and by switching the redox state, adhesion and proliferation of MDCK epithelial cells was controlled as well as stem cell seeding density. Electronically active 3D-scaffolds based on electrospun PET nano-fibers coated with PEDOT have been used as a substrate to culture SH-SY5Y neuroblastoma cells and to induce Ca2+ signaling. Finally, we report on micromechanical stimulation of cells using an electroactive topography surface based on micropattened polypyrrole.

  • 22. Lim, W.
    et al.
    Norton, D. P.
    Pearton, S. J,
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Osinsky, A.
    Dong, J. W.
    Hertog, B.
    Thompson, A. V.
    Schoenfeld, W. V.
    Wang, Y. L.
    Ren, F.
    Migration and Luminescence Enhancement Effects of Deuterium in ZnO/ZnCdO Quantum Wells2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, p. 032103-Article in journal (Refereed)
    Abstract [en]

    ZnO/ZnCdO/ZnO multiple quantum well samples grown on sapphire substrates by molecular beam epitaxy and annealed in situ were exposed to D2 plasmas at 150 °C. The deuterium showed migration depths of ~0.8 µm for 30 min plasma exposures, with accumulation of 2H in the ZnCdO wells. The photoluminescence (PL) intensity from the samples was increased by factors of 5 at 5 K and ~20 at 300 K as a result of the deuteration, most likely due to passivation of competing nonradiative centers. Annealing up to 300 °C led to increased migration of 2H toward the substrate but no loss of deuterium from the sample and little change in the PL intensity. The initial PL intensities were restored by annealing at >=400 °C as 2H was evolved from the sample (~90% loss by 500 °C). By contrast, samples without in situ annealing showed a decrease in PL intensity with deuteration. This suggests that even moderate annealing temperatures lead to degradation of ZnCdO quantum wells.

  • 23.
    Lindgren, Lars
    et al.
    Chalmers University of Technology.
    Zhang, Fengling
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Admassie, Shimelis
    Addis Ababa University.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, M.R.
    Chalmers University of Technology.
    Blue Polymer Light-Emitting Diodes Based on Novel Polymers2005In: 14:th International Conference on Luminescence ICL05,2005, 2005Conference paper (Other academic)
  • 24.
    Lindgren, L.J.
    et al.
    Chalmers Tekniska Högskola.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Synthesis and properties of polyfluorenes with phenyl substituents2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 154, p. 97-100Article in journal (Refereed)
  • 25.
    Lindgren, L.J
    et al.
    CTH.
    Zhang, Fengling
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Admassie, S.
    Addis Abeba university.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Blue light-emitting diodes based on novel polyfluorene copolymers2007In: Journal of Luminescence, ISSN 0022-2313, E-ISSN 1872-7883, Vol. 122-123, no 1-2, p. 610-613Article in journal (Refereed)
    Abstract [en]

    This study presents the synthesis and characterisation of a series of fluorene-based conjugated copolymers, together with the preparation and characterisation of the corresponding light-emitting devices. The polymers consist of alkoxyphenyl-substituted fluorene units together with different amounts of a hole-transporting triphenylamine-substituted fluorene unit: 0%, 10%, 25% and 50%. All polymers (P0, P1, P2, and P3) show high photoluminescence efficiency (ηPL) and light emission (both PL and EL) in the blue spectral region. Electrochemical studies show improved hole injection as the ratio of the triphenylamine-substituted segment is increased. The electroluminescence quantum efficiencies (EQEs) of the devices increase six times going from P0 to P1. Compared with P1, polymers P2 and P3 show lower efficiencies in devices. These findings indicate the presence of an optimal polymer composition, where balance between the charge-carrier mobilities has been reached. © 2006 Elsevier B.V. All rights reserved.

  • 26.
    Persson, Nils-Krister
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Wang, Xiangjun
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Optical limitations in thin-film low-band-gap polymer/fullerene bulk heterojunction devices2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 8, p. 083503-Article in journal (Refereed)
    Abstract [en]

    Photovoltaic devices from the low-band-gap alternating copolymer APFO-Green1, blended with the fullerene derivative BTPF70 as electron acceptor, show a pronounced variation of the external quantum efficiency with varying thickness. Device simulation, based on ellipsometric characterization, reveals that this behavior is to be expected and valid also for most low-band-gap polymers and that it can be explained by optical interference. Requirements for materials suitable for wide spectral coverage in thin-film organic solar cells are delineated. Furthermore, the internal quantum efficiency is calculated to be ≈ 0.4.

  • 27.
    Perzon, Erik
    et al.
    Chalmers University of Technology.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Admassie, Shimelis
    IFM Linköpings university.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, Mats R
    Chalmers university of Technology.
    An alternating low band-gap polyfluorene for optoelectronic devices2006In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 47, p. 4261-4268Article in journal (Refereed)
  • 28.
    Perzon, Erik
    et al.
    Chalmers Tekniska Högskola.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Zhang, Fengling
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Mammo, Wendimagegn
    Chalmers Tekniska Högskola.
    Delgado, Juan Luis
    Universidad de Castilla-La Mancah, Spain.
    de la Cruz, Pilar
    Universidad de Castilla-La Mancha, Spain.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Langa, Fernando
    Universidad de Castilla-La Mancha, Spain.
    Andersson, Mats R
    Chalmers Tekniska Högskola.
    Design, Synthesis and Properties of Low Band Gap Polyfluorenes for Photovoltaic Devices2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 154, p. 53-56Article in journal (Refereed)
  • 29.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C.W.
    University of California, La Jolla, USA .
    Geelhaar, L.
    Paul-Drude-Institut für Festkörpelektronik, Berlin.
    Riechert, H.
    Paul-Drude-Institut für Festkörpelektronik, Berlin.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Studies of spin loss during room-temperature spin injection across a GaNAs/GaAs interface2011In: Abstract book of the 9th Int. Conf. on Nitride Semiconductors, Glasgow, UK, 2011, p. PC1.12-Conference paper (Other academic)
  • 30.
    Puttisong, Yuttapoom
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Carrere, H
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Zhao, F
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Balocchi, A
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Marie, X
    Université de Toulouse, LPCNO: INSA, UPS, CNRS, 135 avenue de Rangueil, 31077 Toulouse Cedex, France.
    Tu, C W
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Electron spin filtering by thin GaNAs/GaAs multiquantum wells2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 5, p. 052104-Article in journal (Refereed)
    Abstract [en]

    Effectiveness of the recently discovered defect-engineered spin-filtering effect is closely examined in GaNAs/GaAs multiquantum wells (QWs) as a function of QW width. In spite of narrow well widths of 3-9 nm, rather efficient spin filtering is achieved at room temperature. It leads to electron spin polarization larger than 18% and an increase in photoluminescence intensity by 65% in the 9 nm wide QWs. A weaker spin filtering effect is observed in the narrower QWs, mainly due to a reduced sheet concentration of spin-filtering defects (e.g., Ga-i interstitial defects).

  • 31.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ptak, Aaron J.
    National Renewable Energy Laboratory, Golden, Colorado, USA.
    Tu, Charles W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Geelhaar, Lutz
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Riechert, Henning
    Paul-Drude-Institut für Festkörpelektronik, Berlin, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Defect-enabled Room-temperature Spin Functionality in Ga(In)NAs2012Conference paper (Other academic)
    Abstract [en]

    Efficient generation, maintaining, manipulation and detection of electron spin polarization and coherence at room-temperature (RT) in semiconductors is a prerequisite for the success of future semiconductor spintronics. Potential spintronic devices are expected to be based on fundamental building blocks such as spin filters (or spin injectors or spin aligners), spin amplifiers and spin detectors. During the past decade spin filters and spin detectors have been a main focal point of intense research efforts in the field of semiconductor spintronics that have led to many innovative approaches and encouraging developments. In contrast, experimental developments in spin amplifiers have been extremely limited. At present, realization of efficient RT spin functionality remains to be a great challenge and a hotly pursued research topic.

    In this work, we explore a new and unconventional approach of defect-enabled spin functionality in a non-magnetic semiconductor without requiring a magnetic layer or external magnetic fields. We demonstrated efficient defect-engineered spin filtering in Ga(In)NAs, which is capable of generating a remarkably high spin polarization degree (> 40%) of conduction electrons at RT. The highest spin polarization achieved to date by using this approach is up to 90 %. We also proposed a conceptually new spin amplifier by defect engineering and provided the first experimental demonstration of an efficient RT spin amplifier based on Ga(In)NAs with a spin gain up to 2700%! Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information, and is predicted to remain functional up to 1 GHz. By taking advantage of the spin amplification effect, we further showed that Ga(In)NAs can be employed as an efficient RT spin detector, with spin detection efficiency well exceeding 100%. Applications of such a spin-functional semiconductor material could potentially provide an attractive and viable solution to the current and important issues on RT spin injection, spin amplification and spin detection in semiconductors for future spintronics.

  • 32.
    Puttisong, Yuttapoom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Tu, C W
    University California San Diego.
    Geelhaar, L
    Paul Drude Institut für Festkörperelektronik.
    Riechert, H
    Paul Drude Institut für Festkörperelektronik.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature spin injection and spin loss across a GaNAs/GaAs interface2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 1, p. 012112-Article in journal (Refereed)
    Abstract [en]

    Recently discovered effect of spin-filtering and spin amplification in GaNAs enables us to reliably obtain detailed information on the degree of spin loss during optical spin injection across a semiconductor heterointerface at room temperature. Spin polarization of electrons injected from GaAs into GaNAs is found to be less than half of what is generated in GaNAs by optical orientation. We show that the observed reduced spin injection efficiency is not only due to spin relaxation in GaAs, but more importantly due to spin loss across the interface due to structural inversion asymmetry and probably also interfacial point defects.

  • 33.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Pearton, S J.
    University of Florida, FL USA .
    Gueorguiev Ivanov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Defects in N, O and N, Zn implanted ZnO bulk crystals2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 10, p. 103509-Article in journal (Refereed)
    Abstract [en]

    Comprehensive characterization of defects formed in bulk ZnO single crystals co-implanted with N and Zn as well as N and O atoms is performed by means of optically detected magnetic resonance (ODMR) complemented by Raman and photoluminescence (PL) spectroscopies. It is shown that in addition to intrinsic defects such as Zn vacancies and Zn interstitials, several N-related defects are formed in the implanted ZnO. The prevailed configuration of the defects is found to depend on the choices of the co-implants and also the chosen annealing ambient. Specifically, co-implantation with O leads to the formation of (i) defects responsible for local vibrational modes at 277, 511, and 581 cm−1; (ii) a N-related acceptor with the binding energy of 160 ± 40 meV that is involved in the donor-acceptor pair emission at 3.23 eV; and (iii) a deep donor and a deep NO acceptor revealed from ODMR. Activation of the latter defects is found to require post-implantation annealing in nitrogen ambient. None of these defects are detected when N is co-implanted with Zn. Under these conditions, the dominant N-induced defects include a deep center responsible for the 3.3128 eV PL line, as well as an acceptor center of unknown origin revealed by ODMR. Formation mechanisms of the studied defects and their role in carrier recombination are discussed.

  • 34.
    von Kieseritzky, F
    et al.
    Royal Inst Technol, Dept Chem, S-10044 Stockholm, Sweden Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Hellberg, J
    Royal Inst Technol, Dept Chem, S-10044 Stockholm, Sweden Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Wang, Xiangjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Regiospecifically alkylated oligothiophenes via structurally defined building blocks2002In: Synthesis (Stuttgart), ISSN 0039-7881, E-ISSN 1437-210X, no 9, p. 1195-1200Article in journal (Refereed)
    Abstract [en]

    We have developed a new synthetic protocol for the unsymmetrically alkylated and halogenated terthiophenes 5 and 10. To demonstrate their usefulness as building blocks for well-defined oligothiophenes, we synthesized a series of seven new sexi-, septi- and octithiophenes. Terthiophene 5 could be dimerized to the didecylsexithiophene In6 and terthiophene 10 to sexithiophene Out6, respectively, by the use of nickel catalysis. Together with the bis-stannylated thiophenes 11 and 12, the septithiophenes In7 and Out7 as well as the octithiophenes In8 and Out8 could be obtained via Stille coupling methodology. We could also obtain the unsymmetrical sexithiophene Unsym6 by selective heterocoupling between one equivalent of terthiophene 5 and 10 each. All new sexi-, septi- and octithiophenes show high photoluminescence in solution, but the quantum yield drops sharply in thin films of the materials.

  • 35.
    Wang, Xiangjun
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Surface Energy Patterning and Optoelectronic Devices Based on Conjugated Polymers2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis concerns surface energy modification and patterning of the surfaces of conjugated polymers. Goniometry and Wilhelmy Balance techniques were used to evaluate the surface energy or wettability of a polymer’s surface; infrared reflectionabsorption spectroscopy (IRAS) was used to analyse the residuals on the surface as modified by a bare elastomeric stamp poly(dimethylsiloxane) (PDMS). The stamp was found to be capable of modifying a polymer surface. Patterning of a single and/or double layer of conjugated polymers on the surface can be achieved by surface energy controlled dewetting. Modification of a conjugated polymer film can also be carried out when a sample is subjected to electrochemical doping in an aqueous electrolyte. The dynamic surface energy changes during the process were monitored in-situ using the Wilhelmy balance method.

    This thesis also concerns studies of conjugated polymer-based optoelectronics, including light-emitting diodes (PLEDs), that generate light by injecting charge into the active polymer layer, and solar cells (PSCs), that create electrical power by absorbing and then converting solar photons into electron/hole pairs. A phosphorescent metal complex was doped into polythiophene to fabricate PLEDs. The energy transfer from the host polymer to the guest phosphorescent metal (iridium and platinum) complex was studied using photoluminescence and electroluminescence measurements performed at room temperature and at liquid nitrogen temperature. PSCs were prepared using low-bandgap polyfluorene copolymers as an electron donor blended with several fullerene derivatives acting as electron acceptors. Energetic match is the main issue affecting efficient charge transfer at the interface between the polymers and the fullerene derivatives, and therefore the performance of the PSCs. Photoluminescence, luminescence quenching and the lowest unoccupied molecular orbital (LUMO) together with the highest occupied molecular orbital (HOMO) of the active materials in the devices were studied. A newly synthesized fullerene, that could match the low-bandgap polymers, was selected and used as electron acceptor in the PSCs. Photovoltaic properties of these PSCs were characterised, demonstrating one of the most efficient polymer:fullerene SCs that generate photocurrent at 1 μm.

    List of papers
    1. PEDOT surface energy pattern controls fluorescent polymer deposition by dewetting
    Open this publication in new window or tab >>PEDOT surface energy pattern controls fluorescent polymer deposition by dewetting
    2004 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 449, no 1-2, p. 125-132Article in journal (Refereed) Published
    Abstract [en]

    An elastomeric stamp of poly(dimethylsiloxane) (PDMS) can modify the surface energy of some surfaces when brought into conformal contact with these for some time. The substrates under investigation are a conducting polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) and a polyelectrolyte poly(sodium 4-styrenesulfonate) (NaPSS). The changes in surface wetting are characterized by contact angle measurement. Changes are due to the PDMS stamp, which leaves low molecular weight residues on the surface, as shown by infrared reflection absorption spectroscopy. This process may also be operating when other inks are transferred in microcontact printing. Patterning of fluorescent polymer film with feature size of 10–100 μm range is done by confining polymer solutions on the modified surface, by means of spin- or dip-coating. The profile of the patterned film and factors that influence the profile are discussed. This technique is a convenient way to build polymer microstructures for application in organic and biomolecular electronics and photonics.

    Keywords
    Surface energy, Surface modification by PDMS stamp, Contact angle analysis, IRA spectrum, Polymer patterning
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13884 (URN)10.1016/j.tsf.2003.10.153 (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
    2. Single and bilayer submicron arrays of fluorescent polymer on conducting polymer surface with surface energy controlled dewetting
    Open this publication in new window or tab >>Single and bilayer submicron arrays of fluorescent polymer on conducting polymer surface with surface energy controlled dewetting
    2005 (English)In: Nanotechnology, ISSN 0957-4484, Vol. 16, p. 437-443Article in journal (Refereed) Published
    Abstract [en]

    Construction of luminescent single- and bilayer polymer arrays in micron and submicron scales through dewetting on a heterogeneous conducting polymer surface is demonstrated. We study the influence of the pattern geometry and film thickness of polymer dewetting upon annealing, and the morphology of created polymer arrays on the heterogeneous surface. The materials used for patterning are an insulating poly(methyl methacrylate) (PMMA) or a conjugated fluorescent polymer, poly(dioctylphenylthiophene) (PDOPT). The substrate used is the conducting polymer poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT–PSS), with modified heterogeneous surface energy obtained by application of a bare polydimethylsiloxane (PDMS) stamp.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13885 (URN)10.1088/0957-4484/16/4/018 (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
    3. In-situ Wilhelmy balance surface energy determination of poly(3-hexylthiophene) and poly(3,4-ethylenedioxythiophene) during electrochemical doping-dedoping
    Open this publication in new window or tab >>In-situ Wilhelmy balance surface energy determination of poly(3-hexylthiophene) and poly(3,4-ethylenedioxythiophene) during electrochemical doping-dedoping
    2006 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 22, p. 9287-9294Article in journal (Refereed) Published
    Abstract [en]

    Changes in the contact angle between conjugated polymers surface poly(3-hexylthiophene) [P3HT] and poly(3,4-ethylenedioxythiophene) (PEDOT) upon electrochemical doping−dedoping in aqueous electrolyte were determined in situ using a Wilhelmy plate tensiometer in an electrochemical cell. The hydrophobic P3HT was less hydrophobic in the oxidized state than in the neutral state; the more hydrophilic PEDOT was less hydrophilic in the oxidized state than when neutral. The tensiometry results were in good agreement with those measured by contact angle goniometry, and further corroborated by the capillary rise upon doping in a fluid cell with two parallel polymer coated plates, another in situ dynamic determination method. The contact angle changes depend on doping potential, electrolyte type, and concentration. We also deconvoluted the surface energy into components of van der Waals and acid−base interactions, using three probe liquids on the polymer surfaces, ex situ the electrochemical cell. The methods and the obtained results are relevant for the science and technology areas of printed electronics and electrochemical devices and for the understanding of surface energy modification by electrochemical doping.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13886 (URN)10.1021/la061606p (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
    4. Electrophosphorescence from substituted poly(thiophene) doped with iridium or platinum complex
    Open this publication in new window or tab >>Electrophosphorescence from substituted poly(thiophene) doped with iridium or platinum complex
    2004 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 468, no 1-2, p. 226-233Article in journal (Refereed) Published
    Abstract [en]

    Electrophosphorescence has been observed in doped polythiophene light-emitting diodes (LEDs) with poly(3-methyl-4-octylthiophene) [PMOT] as host and the phosphorescent compounds bis(2-phenylbenzothiazole) iridium acetylacetonate (BTIr) or platinum(II) 2,8,12,17-tetraethyl-3,7,13,18-tramethyl porphyrin (PtOX) as guest. The photoluminescence (PL) and electroluminescence (EL) of host–phosphorescent guest blends PMOT:BTIr (or PMOT:PtOX) showed the existence of energy transfer from host to guest, which were guest concentration-dependent. At a certain guest concentration, emission from host PMOT was completely quenched in both blends based LEDs, and this gave rise to electrophosphorescence. The PL from host PMOT in the PMOT:BTIr blend film could not be quenched completely but was totally quenched in PMOT:PtOX. This implies a more efficient energy transfer from PMOT to PtOX than that from PMOT to BTIr under optical excitation. Comparison of PL and EL showed that the mechanism of exciton formation at the guest site under electrical excitation was not identical for these two systems. Energy transfer was a dominating route for exciton formation in PMOT:PtOX-based LEDs; charge trapping effect additionally contributed to the formation of exciton at BTIr in PMOT:BTIr-based LEDs. This study demonstrates a new direction in which polythiophene can be a candidate as a host to realize electrophosphorescence in polymer light-emitting diodes (PLEDs). Authors further indicate that to optimize the performance of the polythiophe/phosphorescent complexes, LEDs proper polythiophenes with large bang gap are needed.

    Keywords
    Polymer LED, Electrophosphorescence, Energy transfer, Quenching of luminescence, Polythiophene, Phosphorescent complex
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13887 (URN)10.1016/j.tsf.2004.05.095 (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
    5. Infrared photocurrent spectral response from plastic solar cell with low-bandgap polyfluorene and fullerene derivative
    Open this publication in new window or tab >>Infrared photocurrent spectral response from plastic solar cell with low-bandgap polyfluorene and fullerene derivative
    Show others...
    2004 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 21, p. 5081-5083Article in journal (Refereed) Published
    Abstract [en]

    Plastic solar cells were fabricated using a low-band-gap alternating copolymer of fluorene and a donor–acceptor–donor moiety (APFO-Green1), blended with [6,6]-phenyl-C61-butyric acid methylester or 3-(3,5-Bis-trifluoromethylphenyl)-1-(4-nitrophenyl)pyrazolino[60]fullerene as electron acceptors. The polymer shows optical absorption in two wavelength ranges from 300<<500  nm and 650<<1000  nm. Devices based on APFO-Green1 blended with the later fullerene exhibit an outstanding photovoltaic behavior at the infrared range, where the external quantum efficiency is as high as 8.4% at 840  nm and 7% at 900  nm, while the onset of photogeneration is found at 1  µm. A photocurrent density of 1.76  mA/cm2, open-circuit voltage of 0.54  V, and power conversion efficiency of 0.3% are achieved under the illumination of AM1.5 (1000  W/m2) from a solar simulator.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13888 (URN)10.1063/1.1825070 (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
    6. Enhanced photocurrent spectral response in low-bandgap polyfluorene and C70-Derivative-Based Solar Cells
    Open this publication in new window or tab >>Enhanced photocurrent spectral response in low-bandgap polyfluorene and C70-Derivative-Based Solar Cells
    Show others...
    2005 (English)In: Advanced Functional Materials, ISSN 1616-301X, Vol. 15, no 10, p. 1665-1670Article in journal (Refereed) Published
    Abstract [en]

    Plastic solar cells have been fabricated using a low-bandgap alternating copolymer of fluorene and a donor-acceptor-donor moiety (APFO-Green1), blended with 3-(3,5-bis-trifluoromethylphenyl)-1-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) as electron acceptor. The polymer shows optical absorption in two wavelength ranges, < 500 nm and 600 <  < 1000 nm. The BTPF70 absorbs light at < 700 nm. A broad photocurrent spectral response in the wavelength range 300 <  < 1000 nm is obtained in solar cells. A photocurrent density of 3.4 mA cm-2, open-circuit voltage of 0.58 V, and power-conversion efficiency of 0.7 % are achieved under illumination of AM1.5 (1000 W m-2) from a solar simulator. Synthesis of BTPF70 is presented. Photoluminescence quenching and electrochemical studies are used to discuss photoinduced charge transfer.

    Keywords
    Fullerenes, Polyfluorenes, Solar cells - organic
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13889 (URN)10.1002/adfm.200500114 (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
    7. Polymer solar cells with low-bandgap polymers blended with C70-derivative give photocurrent at 1 μm
    Open this publication in new window or tab >>Polymer solar cells with low-bandgap polymers blended with C70-derivative give photocurrent at 1 μm
    Show others...
    2006 (English)In: Thin Solid Films, ISSN 0040-6090, Vol. 511-512, p. 576-580Article in journal (Refereed) Published
    Abstract [en]

    A new series of low-bandgap alternating polyfluorenes with different donor–acceptor–donor moieties have been synthesized. Electrochemical and optical absorption measurement show that onset bandgaps of these polymers range from 1.2 to 1.5 eV. These polymers, blended with a C70-derivative as acceptor, are used for solar cell fabrication. Devices show promising photovoltaic properties, and the spectral response of photocurrent covers all visible and near-infrared wavelength regions with its onset extended to 1 μm. The best data gives a photocurrent density of 3.4 mA/cm2, open circuit voltage of 0.58 V and power conversion efficiency of 0.7% under illumination of AM1.5 (1000 W/m2) from a solar simulator.

    Keywords
    Low-bandgap; Polyfluorene; Fullerene C70-derivative; Solar cell
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13890 (URN)10.1016/j.tsf.2005.12.013 (DOI)
    Available from: 2006-07-07 Created: 2006-07-07 Last updated: 2018-10-08
  • 36.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Department of Organic Chemistry and Polymer Technology, Chalmers University of Technology, Göteborg, Sweden.
    Thomson, Mark E.
    Department of Chemistry, University of Southern California, Los Angeles, USA.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Electrophosphorescence from substituted poly(thiophene) doped with iridium or platinum complex2004In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 468, no 1-2, p. 226-233Article in journal (Refereed)
    Abstract [en]

    Electrophosphorescence has been observed in doped polythiophene light-emitting diodes (LEDs) with poly(3-methyl-4-octylthiophene) [PMOT] as host and the phosphorescent compounds bis(2-phenylbenzothiazole) iridium acetylacetonate (BTIr) or platinum(II) 2,8,12,17-tetraethyl-3,7,13,18-tramethyl porphyrin (PtOX) as guest. The photoluminescence (PL) and electroluminescence (EL) of host–phosphorescent guest blends PMOT:BTIr (or PMOT:PtOX) showed the existence of energy transfer from host to guest, which were guest concentration-dependent. At a certain guest concentration, emission from host PMOT was completely quenched in both blends based LEDs, and this gave rise to electrophosphorescence. The PL from host PMOT in the PMOT:BTIr blend film could not be quenched completely but was totally quenched in PMOT:PtOX. This implies a more efficient energy transfer from PMOT to PtOX than that from PMOT to BTIr under optical excitation. Comparison of PL and EL showed that the mechanism of exciton formation at the guest site under electrical excitation was not identical for these two systems. Energy transfer was a dominating route for exciton formation in PMOT:PtOX-based LEDs; charge trapping effect additionally contributed to the formation of exciton at BTIr in PMOT:BTIr-based LEDs. This study demonstrates a new direction in which polythiophene can be a candidate as a host to realize electrophosphorescence in polymer light-emitting diodes (PLEDs). Authors further indicate that to optimize the performance of the polythiophe/phosphorescent complexes, LEDs proper polythiophenes with large bang gap are needed.

  • 37.
    Wang, Xiangjun
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Berggren, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Dynamic Control of Surface Energy and Topography of Microstructured Conducting Polymer Films2008In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 24, p. 5942-5948Article in journal (Refereed)
    Abstract [en]

     Microstructured polymer surfaces, including conducting and insulating polymers, have been prepared to achieve electrochemical control of the surface energy and topography. The reported surface switches include pillar- and mesh-like surface patterns of polypyrrole (PPy), poly(3,4-ethylene-dioxythiophene) (PEDOT), and photoresists. The structures have been evaluated by contact angle measurements and optical and scanning electron microscopy to determine the surfaces characteristics. These microstructured polymer surface switches can be electrochemically modified from dewetting to wetting conditions, with a maximum associated change of the water contact angle from 129° to 44°. This contact angle switching was observed for samples in which dynamic control of the surface topography and surface tension was coupled. Control of topography was achieved with a dynamic height-switching range of more than 3 ìm. In addition, dynamic control of anisotropic wetting is reported. Our experiments were carried out under conditions that are suitable for a biointerface, implying potential application in biotechnology and cell science. In particular, switching of the energy, chemistry, and topography of the surface, along with their associated orientation, are interesting features for dynamic (electronic) control of the seeding and proliferation for living cells. The technology reported promises for electronically controlled cell-growth within Petri dishes, well plates, and other cell-hosting tools. 

  • 38.
    Wang, Xiangjun
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Buyanova, Irina A.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pan, C.J.
    Department of Electrical and Computer Engineering, University of California, La Jolla, United States, Optical Sciences Center, National Central University, Jhongli, Taoyuan 32001, Taiwan.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, United States.
    Optical characterization studies of grown-in defects in ZnO epilayers grown by molecular beam epitaxy2007In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 401-402, p. 413-416Article in journal (Refereed)
    Abstract [en]

    Defect formation in ZnO epilayers grown by molecular beam epitaxy (MBE) is studied by employing optical characterization techniques such as photoluminescence (PL) and optically detected magnetic resonance (ODMR). Excess of oxygen during the growth was found to cause an appearance of the PL peak at around 3.338 eV, which indicates that the corresponding defects are predominantly formed in O-rich ZnO. On the other hand, non-stoichiometry during the growth was singled out as the main factor facilitating formation of defects involved in the yellow PL emission band peaking at around 2.17 eV. Several magnetic-resonance active defects are revealed via monitoring this emission and their magnetic-resonance signatures are obtained. © 2007 Elsevier B.V. All rights reserved.

  • 39.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Ederth, Thomas
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    In-situ Wilhelmy balance surface energy determination of poly(3-hexylthiophene) and poly(3,4-ethylenedioxythiophene) during electrochemical doping-dedoping2006In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 22, no 22, p. 9287-9294Article in journal (Refereed)
    Abstract [en]

    Changes in the contact angle between conjugated polymers surface poly(3-hexylthiophene) [P3HT] and poly(3,4-ethylenedioxythiophene) (PEDOT) upon electrochemical doping−dedoping in aqueous electrolyte were determined in situ using a Wilhelmy plate tensiometer in an electrochemical cell. The hydrophobic P3HT was less hydrophobic in the oxidized state than in the neutral state; the more hydrophilic PEDOT was less hydrophilic in the oxidized state than when neutral. The tensiometry results were in good agreement with those measured by contact angle goniometry, and further corroborated by the capillary rise upon doping in a fluid cell with two parallel polymer coated plates, another in situ dynamic determination method. The contact angle changes depend on doping potential, electrolyte type, and concentration. We also deconvoluted the surface energy into components of van der Waals and acid−base interactions, using three probe liquids on the polymer surfaces, ex situ the electrochemical cell. The methods and the obtained results are relevant for the science and technology areas of printed electronics and electrochemical devices and for the understanding of surface energy modification by electrochemical doping.

  • 40.
    Wang, Xiangjun
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Olafsson, S
    Madsen, LD
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Swedish Def Res Agcy, FOI, SE-58111 Linkoping, Sweden Royal Inst Technol, Dept Condensed Matter Phys, SE-16440 Stockholm, Sweden.
    Rudner, S
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Grishin, A
    Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Swedish Def Res Agcy, FOI, SE-58111 Linkoping, Sweden Royal Inst Technol, Dept Condensed Matter Phys, SE-16440 Stockholm, Sweden.
    Helmersson, Ulf
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics .
    Growth and characterization of Na0.5K0.5NbO3 thin films on polycrystalline Pt80Ir20 substrates2002In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 17, no 5, p. 1183-1191Article in journal (Refereed)
    Abstract [en]

    Na0.5K0.5NbO3 thin films have been deposited onto textured polycrystalline Pt80Ir20 substrates using radio frequency magnetron sputtering. Films were grown in off- and on-axis positions relative to the target at growth temperatures of 500-700 degreesC and sputtering pressures of 1-7 Pa. The deposited films were found to be textured, displaying a mixture of two orientations (001) and (101). Films grown on-axis showed a prefered (001) orientation, while the off-axis films had a (101) orientation. Scanning electron microscopy showed that the morphology of the films was dependent on the substrate position and sputtering pressure. The low-frequency (10 kHz) dielectric constants of the films were found to be in the range of approximately 490-590. Hydrostatic piezoelectric measurements showed that the films were piezoelectric in the as-deposited form with a constant up to 14.5 pC/N.

  • 41.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Perzon, Erik
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
    Delgado, Juan Luis
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla—La Mancha, Toledo, Spain.
    de la Cruz, Pilar
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla—La Mancha, Toledo, Spain.
    Zhang, Fengling
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Langa, Fernando
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla—La Mancha, Toledo, Spain.
    Andersson, Mats
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Infrared photocurrent spectral response from plastic solar cell with low-bandgap polyfluorene and fullerene derivative2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 21, p. 5081-5083Article in journal (Refereed)
    Abstract [en]

    Plastic solar cells were fabricated using a low-band-gap alternating copolymer of fluorene and a donor–acceptor–donor moiety (APFO-Green1), blended with [6,6]-phenyl-C61-butyric acid methylester or 3-(3,5-Bis-trifluoromethylphenyl)-1-(4-nitrophenyl)pyrazolino[60]fullerene as electron acceptors. The polymer shows optical absorption in two wavelength ranges from 300<<500  nm and 650<<1000  nm. Devices based on APFO-Green1 blended with the later fullerene exhibit an outstanding photovoltaic behavior at the infrared range, where the external quantum efficiency is as high as 8.4% at 840  nm and 7% at 900  nm, while the onset of photogeneration is found at 1  µm. A photocurrent density of 1.76  mA/cm2, open-circuit voltage of 0.54  V, and power conversion efficiency of 0.3% are achieved under the illumination of AM1.5 (1000  W/m2) from a solar simulator.

  • 42.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Perzon, Erik
    Mammo, Wendimagegn
    Oswald, Frédéric
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Toledo, Spain.
    Admassie, Shimelis
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Persson, Nils-Krister
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Langa, Fernando
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Toledo, Spain.
    Andersson, Mats R.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Polymer solar cells with low-bandgap polymers blended with C70-derivative give photocurrent at 1 μm2006In: Thin Solid Films, ISSN 0040-6090, Vol. 511-512, p. 576-580Article in journal (Refereed)
    Abstract [en]

    A new series of low-bandgap alternating polyfluorenes with different donor–acceptor–donor moieties have been synthesized. Electrochemical and optical absorption measurement show that onset bandgaps of these polymers range from 1.2 to 1.5 eV. These polymers, blended with a C70-derivative as acceptor, are used for solar cell fabrication. Devices show promising photovoltaic properties, and the spectral response of photocurrent covers all visible and near-infrared wavelength regions with its onset extended to 1 μm. The best data gives a photocurrent density of 3.4 mA/cm2, open circuit voltage of 0.58 V and power conversion efficiency of 0.7% under illumination of AM1.5 (1000 W/m2) from a solar simulator.

  • 43.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Perzon, Erik
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
    Oswald, Frédéric
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Toledo, Spain.
    Langa, Fernando
    Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La Mancha, Toledo, Spain.
    Admassie, Shimelis
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Enhanced photocurrent spectral response in low-bandgap polyfluorene and C70-Derivative-Based Solar Cells2005In: Advanced Functional Materials, ISSN 1616-301X, Vol. 15, no 10, p. 1665-1670Article in journal (Refereed)
    Abstract [en]

    Plastic solar cells have been fabricated using a low-bandgap alternating copolymer of fluorene and a donor-acceptor-donor moiety (APFO-Green1), blended with 3-(3,5-bis-trifluoromethylphenyl)-1-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) as electron acceptor. The polymer shows optical absorption in two wavelength ranges, < 500 nm and 600 <  < 1000 nm. The BTPF70 absorbs light at < 700 nm. A broad photocurrent spectral response in the wavelength range 300 <  < 1000 nm is obtained in solar cells. A photocurrent density of 3.4 mA cm-2, open-circuit voltage of 0.58 V, and power-conversion efficiency of 0.7 % are achieved under illumination of AM1.5 (1000 W m-2) from a solar simulator. Synthesis of BTPF70 is presented. Photoluminescence quenching and electrochemical studies are used to discuss photoinduced charge transfer.

  • 44.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Single and bilayer submicron arrays of fluorescent polymer on conducting polymer surface with surface energy controlled dewetting2005In: Nanotechnology, ISSN 0957-4484, Vol. 16, p. 437-443Article in journal (Refereed)
    Abstract [en]

    Construction of luminescent single- and bilayer polymer arrays in micron and submicron scales through dewetting on a heterogeneous conducting polymer surface is demonstrated. We study the influence of the pattern geometry and film thickness of polymer dewetting upon annealing, and the morphology of created polymer arrays on the heterogeneous surface. The materials used for patterning are an insulating poly(methyl methacrylate) (PMMA) or a conjugated fluorescent polymer, poly(dioctylphenylthiophene) (PDOPT). The substrate used is the conducting polymer poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT–PSS), with modified heterogeneous surface energy obtained by application of a bare polydimethylsiloxane (PDMS) stamp.

  • 45.
    Wang, Xiangjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Östblom, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Johansson, Tomas
    Linköping University, Department of Physics, Chemistry and Biology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    PEDOT surface energy pattern controls fluorescent polymer deposition by dewetting2004In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 449, no 1-2, p. 125-132Article in journal (Refereed)
    Abstract [en]

    An elastomeric stamp of poly(dimethylsiloxane) (PDMS) can modify the surface energy of some surfaces when brought into conformal contact with these for some time. The substrates under investigation are a conducting polymer poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) and a polyelectrolyte poly(sodium 4-styrenesulfonate) (NaPSS). The changes in surface wetting are characterized by contact angle measurement. Changes are due to the PDMS stamp, which leaves low molecular weight residues on the surface, as shown by infrared reflection absorption spectroscopy. This process may also be operating when other inks are transferred in microcontact printing. Patterning of fluorescent polymer film with feature size of 10–100 μm range is done by confining polymer solutions on the modified surface, by means of spin- or dip-coating. The profile of the patterned film and factors that influence the profile are discussed. This technique is a convenient way to build polymer microstructures for application in organic and biomolecular electronics and photonics.

  • 46.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Zhao, F
    Université de Toulouse.
    Lagarde, D
    Université de Toulouse.
    Balocchi, A
    Université de Toulouse.
    Marie, X
    Université de Toulouse.
    Tu, C W
    University of California.
    Harmand, J C
    LPN, France.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Room-temperature defect-engineered spin filter based on a non-magnetic semiconductor.2009In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 8, no 3, p. 198-202Article in journal (Refereed)
    Abstract [en]

    Generating, manipulating and detecting electron spin polarization and coherence at room temperature is at the heart of future spintronics and spin-based quantum information technology. Spin filtering, which is a key issue for spintronic applications, has been demonstrated by using ferromagnetic metals, diluted magnetic semiconductors, quantum point contacts, quantum dots, carbon nanotubes, multiferroics and so on. This filtering effect was so far restricted to a limited efficiency and primarily at low temperatures or under a magnetic field. Here, we provide direct and unambiguous experimental proof that an electron-spin-polarized defect, such as a Ga(i) self-interstitial in dilute nitride GaNAs, can effectively deplete conduction electrons with an opposite spin orientation and can thus turn the non-magnetic semiconductor into an efficient spin filter operating at room temperature and zero magnetic field. This work shows the potential of such defect-engineered, switchable spin filters as an attractive alternative to generate, amplify and detect electron spin polarization at room temperature without a magnetic material or external magnetic fields.

  • 47.
    Wang, Xingjun
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hong, Y. G.
    Department of Electrical and Computer Engineering Univeristy of California, La Jolla, California 92093, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering University of California, La Jolla, California 92093, USA.
    Effects of grown-in defects on electron spin polarization in dilute nitride alloys2008In: 7th International Conference on Nitride Semiconductors ICNS-7,2007, phys. stat. sol. (c) vol. 5: WILEYVCH Verlag GmbH & Co. KGaA, Weinheim , 2008, p. 1529-Conference paper (Refereed)
    Abstract [en]

    Strong electron spin polarization in GaNAs epilayers and multiple quantum well structures is observed upon optical orientation at room temperature. The effect is explained in terms of spin dependent recombination (SDR) involving deep paramagnetic defects formed upon N incorporation in GaNAs. Concentration of the corresponding defects is shown to be enhanced during growth at low temperatures but is suppressed by post-growth annealing. Optically detected magnetic resonance (ODMR) measurements performed in the studied structures reveal two paramagnetic defects participating in carrier recombination. One of them is identified as a complex involving AsGa antisite. Correlation between concentrations of the defects monitored via ODMR and in optical orientation measurements is observed which suggests that the same defects may be involved in both processes.

  • 48.
    Wang, Xingjun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Izadifard, M.
    Department of Physics, Shahrood University of Technology, Shahrood, Iran .
    Rawal, S.
    Department of Materials Science and Engineering, University of Florida, Gainesville, Florida.
    Norton, D.P.
    Department of Materials Science and Engineering, University of Florida, Gainesville, Florida.
    Pearton, S.J.
    Department of Materials Science and Engineering, University of Florida, Gainesville, Florida.
    Osinsky, A.
    SVT Associates, Eden Prairie, Minnesota.
    Dong, J.W.
    SVT Associates, Eden Prairie, Minnesota.
    Dabiran, A.
    SVT Associates, Eden Prairie, Minnesota.
    Band gap properties of Zn1−xCdxO alloys grown by molecular-beam epitaxy2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, p. 151909-Article in journal (Refereed)
    Abstract [en]

    Optical absorption and reflectance measurements are performed to evaluate compositional and temperature dependences of band gap energies of Zn1−xCdxO alloys grown by molecular-beam epitaxy. The compositional dependence of the band gap energy, determined by taking into account excitonic contributions, is shown to follow the trend Eg(x) = 3.37−2.82x+0.95x2. Incorporation of Cd was also shown to somewhat slow down thermal variation of the band gap energies, beneficial for future device applications.

  • 49.
    Wang, Xingjun
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pan, C. J.
    Tu, C. W.
    Grown-in defects in molecular beam epitaxial ZnO2007In: XVI International Materials Research Congress,2007, 2007Conference paper (Other academic)
  • 50.
    Wang, Xingjun
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pan, C.J.
    Tu, C.W.
    Effects of stoichiometry on defect formation in ZnO epilayers grown by molecular-beam epitaxy: An optically detected magnetic resonance study2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 2, p. 023712-Article in journal (Refereed)
    Abstract [en]

    Photoluminescence (PL) and optically detected magnetic resonance are employed to study effects of nonstoichiometry during the growth on defect formation in ZnO epilayers grown by molecular-beam epitaxy (MBE). Several defects are revealed via monitoring the yellow PL emission (∼2.17 eV) and their magnetic resonance signatures are obtained. The defects are concluded to be common for the MBE growth and are facilitated during the off-stoichiometric growth conditions, especially under excess of oxygen. © 2008 American Institute of Physics.

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