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  • 1.
    Holtz, Per-Olf
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Moskalenko, E
    n/a.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Schoenfeld, W
    n/a.
    Petroff, P M
    n/a.
    Tuning of the charge state of a single InAs/GaAs quantum dot by an external field2009In: Taiwan-Sweden Workshop on Nano Science and Technology, Chi-Tou, Taiwan, 2009Conference paper (Refereed)
  • 2. Khranovskyy, V
    et al.
    Tsiaoussis, I
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Larsson, Arvid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Size tuning of uniformly oriented ZnO nanostructures2008In: Nanotech 2008,2008, 2008Conference paper (Refereed)
  • 3.
    Khranovskyy, Volodymyr
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Tsiaoussis, I
    Aristotle University Thessaloniki, GR-54006 Thessaloniki, Greece .
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Nanointegration of ZnO with Si and SiC2009In: PHYSICA B-CONDENSED MATTER, ISSN 0921-4526, Vol. 404, no 22, p. 4359-4363Article in journal (Refereed)
    Abstract [en]

    The study is dedicated to some aspects of the controlled heteroepitaxial growth of nanoscaled ZnO structures and an investigation of their general and dimension mediated properties. ZnO nanostructures were synthesized by optimized MOCVD process via two growth approaches: (i) catalyst free self-organized growth of ZnO on Si substrates and (ii) ZnO heteroepitaxy on p-type hexagonal 4H-SiC substrates. The SiC substrate was prepared by sublimation epitaxy and served as a template for the ZnO epitaxial growth. The epitaxial growth of n-ZnO on p-SiC resulted in a regular matrix of well-faceted hexagonally shaped ZnO single crystals. The achievement of ZnO integration with Si encompasses controlled growth of vertically oriented nanosized ZnO pillars. The grown structures were characterized by transmission electron microscopy and microphotoluminescence. Low concentration of native defects due to a stoichiometry balance, advanced optical emission, (excitonic type near-band-edge emission and negligible defect related luminescence) and continuous interfaces (epitaxial relationship ZnO[0 0 0 1]/ SiC[0 0 0 1]) are evidenced. The ZnO nanopillars were further probed as field emitters: the grown structures exhibits advanced field emission properties, which are explained in term of dimensionality and spatial uniformity of the nanopillars. The present results contribute to understanding and resolving growth and device related issues of ZnO as a functional nanostructured material.

  • 4.
    Khranovskyy, Volodymyr
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yazdi, Gholamreza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Larsson, Arvid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Hussain, S
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Growth and characterization of ZnO nanostructured material2008In: Journal of Optoelectronics and Advanced Materials, ISSN 1454-4164, E-ISSN 1841-7132, Vol. 10, no 11, p. 2969-2975Article in journal (Refereed)
    Abstract [en]

    ZnO is a wide band gap (3.37 eV) semiconductor material with a high exciton binding energy (60 meV) at room temperature, which is a prerequisite for realization of efficient and stable optoelectronic systems. We demonstrated the APMOCVD growth of nanostructured ZnO material on Si and SiC with advanced emitting properties. The comparison of the properties of nanostructured polycrystalline layers with spatially disconnected ZnO nanocrystals clearly showed the advantage of the latter structures. Such structures distinctively luminesce in the UV range of the spectrum due to excitonic emission, while the contribution of the defect related luminescence is negligible. The significant improvement of the PL properties can be related to the decreased number of non-radiative recombination centers in the nanocrystals of high structural quality.

  • 5.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Optical spectroscopy of InGaAs quantum dots2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The work presented in this thesis deals with optical studies of semiconductor quantum dots (QDs) in the InGaAs material system. It is shown that for self-assembled InAs QDs, the interaction with the surrounding GaAs barrier and the InAs wetting layer (WL) in particular, has a very large impact on their optical properties.

    The ability to control the charge state of individual QDs is demonstrated and attributed to a modulation in the carrier transport dynamics in the WL. After photo-excitation of carriers (electrons and holes) in the barrier, they will migrate in the sample and with a certain probability become captured into a QD. During this migration, the carriers can be affected by exerting them to an external magnetic field or by altering the temperature.

    An external magnetic field applied perpendicular to the carrier transport direction will lead to a decrease in the carrier drift velocity since their trajectories are bent, and at sufficiently high field strength become circular. In turn, this decreases the probability for the carriers to reach the QD since the probability for the carriers to get trapped in WL localizing potentials increases. An elevated temperature leads to an increased escape rate out of these potentials and again increases the flow of carriers towards the QD. These effects have significantly different strengths for electrons and holes due to the large difference in their respective masses and therefore it constitutes a way to control the supply of charges to the QD.

    Another effect of the different capture probabilities for electrons and holes into a QD that is explored is the ability to achieve spin polarization of the neutral exciton (X0). It has been concluded frequently in the literature that X0 cannot maintain its spin without application of an external magnetic field, due to the anisotropic electron – hole exchange interaction (AEI). In our studies, we show that at certain excitation conditions, the AEI can be by-passed since an electron is captured faster than a hole into a QD. The result is that the electron will populate the QD solely for a certain time window, before the hole is captured. During this time window and at polarized excitation, which creates spin polarized carriers, the electron can polarize the QD nuclei. In this way, a nuclear magnetic field is built up with a magnitude as high as ~ 1.5 T. This field will stabilize the X0 spin in a similar manner as an external magnetic field would. The build-up time for this nuclear field was determined to be ~ 10 ms and the polarization degree achieved for X0 is ~ 60 %.

    In contrast to the case of X0, the AEI is naturally cancelled for the negatively charged exciton (X-) and the positively charged exciton (X+) complexes. This is due to the fact that the electron (hole) spin is paired off in case of X- (X+).  Accordingly, an even higher polarization degree (~ 73 %) is measured for the positively charged exciton.

    In a different study, pyramidal QD structures were employed. In contrast to fabrication of self-assembled QDs, the position of QDs can be controlled in these samples as they are grown in inverted pyramids that are etched into a substrate. After sample processing, the result is free-standing AlGaAs pyramids with InGaAs QDs inside. Due to the pyramidal shape of these structures, the light extraction is considerably enhanced which opens up possibilities to study processes un-resolvable in self-assembled QDs. This has allowed studies of Auger-like shake-up processes of holes in single QDs. Normally, after radiative recombination of X+, the QD is populated with a ground state hole. However, at recombination, a fraction of the energy can be transferred to the hole so that it afterwards occupies an excited state instead. This process is detected experimentally as a red-shifted luminescence satellite peak with an intensity on the order of ~ 1/1000 of the main X+ peak intensity. The identification of the satellite peak is based on its intensity correlation with the X+ peak, photoluminescence excitation measurements and on magnetic field measurements.

    List of papers
    1. Effective tuning of the charge state of a single InAs/GaAs quantum dot by an external magnetic field
    Open this publication in new window or tab >>Effective tuning of the charge state of a single InAs/GaAs quantum dot by an external magnetic field
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    2008 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 7, p. 075306-Article in journal (Refereed) Published
    Abstract [en]

    A microphotoluminescence study of single InAs/GaAs quantum dots (QDs) in the presence of an applied external magnetic field is presented. Attention is focused on the redistribution between the spectral lines of a single QD observed at increasing magnetic field parallel to the growth direction (Faraday geometry). The redistribution effect is explained by considering the electron drift velocity in the QD plane that affects the probability for capture into the QD. In contrast, no redistribution is observed when applying the magnetic field perpendicular to the growth direction (Voigt geometry).

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-16333 (URN)10.1103/PhysRevB.78.075306 (DOI)
    Note

    Original Publication: Evgenii Moskalenko, Andréas Larsson, Mats Larsson, Per-Olof Holtz, W. V. Schoenfeld and P. M. Petroff, Effective tuning of the charge state of a single InAs/GaAs quantum dot by an external magnetic field, 2008, Physical Review B Condensed Matter, (78), 075306. http://dx.doi.org/10.1103/PhysRevB.78.075306 Copyright: American Physical Society http://www.aps.org/

    Available from: 2009-01-15 Created: 2009-01-15 Last updated: 2017-12-14Bibliographically approved
    2. Comparative Magneto-Photoluminescence Study of Ensembles and of Individual InAs Quantum Dots
    Open this publication in new window or tab >>Comparative Magneto-Photoluminescence Study of Ensembles and of Individual InAs Quantum Dots
    Show others...
    2009 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 1, p. 353-359Article in journal (Refereed) Published
    Abstract [en]

    We report on magneto-photoluminescence studies of InAs/GaAs quantum dots (QDs) of considerably different densities, from dense ensembles down to individual dots. It is found that a magnetic field applied in Faraday geometry decreases the photoluminescence (PL) intensity of OD ensembles, which is not accompanied by the corresponding increase of PL signal of the wetting layer on which ON are grown. The model suggested to explain these data assumes considerably different strengths of suppression of electron and hole fluxes by a magnetic field. This idea has been successfully checked in experiments on individual ON, where the PL spectra allow to directly monitor the charge state of a OD and, hence, to conclude about relative magnitudes of electron and hole fluxes toward the QD. Comparative studies of different individual QDs have revealed that the internal electric field in the sample (which was altered in the experiments in a controllable way) together with an external magnetic field will determine the charge state and emission intensity of the QDs.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-16615 (URN)10.1021/nl803148q (DOI)
    Available from: 2009-02-07 Created: 2009-02-06 Last updated: 2017-12-14Bibliographically approved
    3. Temperature and Magnetic Field Effects on the Transport Controlled Charge State of a Single Quantum Dot
    Open this publication in new window or tab >>Temperature and Magnetic Field Effects on the Transport Controlled Charge State of a Single Quantum Dot
    2010 (English)In: NANOSCALE RESEARCH LETTERS, ISSN 1931-7573, Vol. 5, no 7, p. 1150-1155Article in journal (Refereed) Published
    Abstract [en]

    Individual InAs/GaAs quantum dots are studied by micro-photoluminescence. By varying the strength of an applied external magnetic field and/or the temperature, it is demonstrated that the charge state of a single quantum dot can be tuned. This tuning effect is shown to be related to the in-plane electron and hole transport, prior to capture into the quantum dot, since the photo-excited carriers are primarily generated in the barrier.

    Place, publisher, year, edition, pages
    Springer Science Business Media, 2010
    Keywords
    Quantum dot; Wetting layer; Magnetic field; Temperature dependence; Charge state
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-58223 (URN)10.1007/s11671-010-9618-x (DOI)000279674400012 ()
    Note
    The original publication is available at www.springerlink.com: L. Arvid Larsson, Mats Larsson, E. S. Moskalenko and Per-Olof Holtz, Temperature and Magnetic Field Effects on the Transport Controlled Charge State of a Single Quantum Dot, 2010, NANOSCALE RESEARCH LETTERS, (5), 7, 1150-1155. http://dx.doi.org/10.1007/s11671-010-9618-x Copyright: Springer Science Business Media http://www.springerlink.com/ Available from: 2010-08-10 Created: 2010-08-09 Last updated: 2011-02-03Bibliographically approved
    4. Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field
    Open this publication in new window or tab >>Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field
    2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 19, p. 193413-Article in journal (Refereed) Published
    Abstract [en]

    A high degree of spin polarization for the neutral exciton in individual quantum dots, at zero external magnetic field, is monitored. While a high polarization degree is commonly observed for the charged exciton, a negligible polarization has been predicted for the neutral exciton. The exceptionally high polarization (andgt;60%) observed here is explained in terms of a dynamical nuclear polarization field, stabilizing the electron spin. Such polarization of the quantum dot nuclei, in case of the neutral exciton, is possible due to unequal capture time of electrons and holes.

    Keywords
    electron spin polarisation, excitons, III-V semiconductors, indium compounds, semiconductor quantum dots
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-52822 (URN)10.1103/PhysRevB.80.193413 (DOI)
    Note
    Original Publication: Evgenii Moskalenko, L A Larsson and Per-Olof Holtz, Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field, 2009, PHYSICAL REVIEW B, (80), 19, 193413. http://dx.doi.org/10.1103/PhysRevB.80.193413 Copyright: American Physical Society http://www.aps.org/ Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
    5.
    The record could not be found. The reason may be that the record is no longer available or you may have typed in a wrong id in the address field.
    6. Manipulating the Spin Polarization of Excitons in a Single Quantum Dot by Optical Means
    Open this publication in new window or tab >>Manipulating the Spin Polarization of Excitons in a Single Quantum Dot by Optical Means
    2011 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 7, p. 071906-Article in journal (Refereed) Published
    Abstract [en]

    Circular polarization studies of photoluminescence from the neutral (X0) and the positively charged (X+) exciton are reported for individual InAs/GaAs quantum dots (QDs). High polarization degrees, 60 % for X0 and 73 % for X+, were recorded without any external magnetic field applied. These studies show that that the QD polarization and population dynamics are controllable either by varying the photo-excitation intensity, or by using a second IR laser excitation.

    Place, publisher, year, edition, pages
    American Institute of Physics, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-64725 (URN)10.1063/1.3554422 (DOI)000287507200017 ()
    Note
    Original Publication: Arvid Larsson, Evgenii Moskalenko and Per-Olof Holtz, Manipulating the Spin Polarization of Excitons in a Single Quantum Dot by Optical Means, 2011, Applied Physics Letters, (98), 7, 071906. http://dx.doi.org/10.1063/1.3554422 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2011-02-03 Created: 2011-02-03 Last updated: 2017-12-11Bibliographically approved
    7. Hole Shake-Up in Individual InGaAs Quantum Dots
    Open this publication in new window or tab >>Hole Shake-Up in Individual InGaAs Quantum Dots
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    We report on a spectroscopic study of hole shake-up processes in single InGaAs quantum dots. By studying dots with very high luminescence efficiency these processes are unveiled and further tested in an applied magnetic field. The mechanism is attributed to shake-up of a hole from the S ground state to the D excited state. The experimental results are confirmed by configuration interaction calculations that also reveal a dependence of the shake-up intensity on the relative extension of electron and hole wave functions.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-64726 (URN)
    Available from: 2011-02-03 Created: 2011-02-03 Last updated: 2016-06-07Bibliographically approved
  • 6.
    Larsson, Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Dufåker, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Functionalisation of ZnO Nanoparticles Using Organic Acids2009In: Nordic Semiconductor Meeting, June 2009 , Reykjavik, 2009Conference paper (Refereed)
  • 7.
    Larsson, Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Karlsson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dufåker, Daniel
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dimastrodonato, V.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Mereni, L. O.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Pelucchi, E.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Hole Shake-Up in Individual InGaAs Quantum DotsManuscript (preprint) (Other academic)
    Abstract [en]

    We report on a spectroscopic study of hole shake-up processes in single InGaAs quantum dots. By studying dots with very high luminescence efficiency these processes are unveiled and further tested in an applied magnetic field. The mechanism is attributed to shake-up of a hole from the S ground state to the D excited state. The experimental results are confirmed by configuration interaction calculations that also reveal a dependence of the shake-up intensity on the relative extension of electron and hole wave functions.

  • 8.
    Larsson, Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Moskalenko, E.S.
    Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg, Russian Federation.
    Magnetic field enabled charge state control of single InAs/GaAs quantum dots2009In: 2009 9th IEEE Conference on Nanotechnology, IEEE NANO 2009, 2009, p. 510-512Conference paper (Refereed)
    Abstract [en]

    Micro-photoluminescence in the presence of an external magnetic field is employed to study individual InAs/GaAs quantum dots (QDs). By varying the strength of the applied magnetic field, the charge state of the QD is tuned from a double negatively charged exciton to a neutral exciton. This effect is shown to be related to carrier transport in the QD-plane prior to capture into the QD. The temperature dependence of the tuning effect is discussed. © 2009 IEEE NANO Organizers.

  • 9.
    Larsson, Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Moskalenko, E
    Ioffe Inst.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Effective tuning of the charge state of a single InAs/GaAs quantum dot by means of external fields2009In: IEEE Nano 2009 in Genua, 2009Conference paper (Refereed)
  • 10.
    Larsson, Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Moskalenko, E
    n/a.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Tuning of the charge state of a single InAs/GaAs quantum dot by means of external fields2009In: Nordic Semiconductor Meeting, Reykavik, 2009Conference paper (Refereed)
  • 11.
    Larsson, Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Moskalenko, Evgenii
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Manipulating the Spin Polarization of Excitons in a Single Quantum Dot by Optical Means2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 7, p. 071906-Article in journal (Refereed)
    Abstract [en]

    Circular polarization studies of photoluminescence from the neutral (X0) and the positively charged (X+) exciton are reported for individual InAs/GaAs quantum dots (QDs). High polarization degrees, 60 % for X0 and 73 % for X+, were recorded without any external magnetic field applied. These studies show that that the QD polarization and population dynamics are controllable either by varying the photo-excitation intensity, or by using a second IR laser excitation.

  • 12.
    Larsson, Arvid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Moskalenko, Evgenii
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Charge state control of single InAs/GaAs quantum dots by means of an external magnetic field2008In: in PHYSICS OF SEMICONDUCTORS, vol 1199, AIP , 2008, p. 297-298Conference paper (Refereed)
    Abstract [en]

    Individual InAs/GaAs quantum dots (QDs) are studied with micro-photoluminescence in the presence of an applied external magnetic field. Attention is focused on the redistribution between the spectral lines of a single QD observed at increased external magnetic field when the magnetic field is applied parallel to the growth direction (Faraday geometry). The effect is shown to be transport related as the electron drift velocity in the QD-plane is decreased by the applied magnetic field and this affects the probability for electron capture into the QD.

  • 13.
    Larsson, Arvid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Moskalenko, Evgenii
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Tuning of the charge state of InAs/GaAs quantum dot by a magnetic field2007In: Nordic Semiconductor Meeting, NSM22,2007, 2007Conference paper (Other academic)
    Abstract [en]

      

  • 14.
    Larsson, Arvid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Moskalenko, Evgeny
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Charge state tuning of individual InAs/GaAs quantum dots by an external magnetic field2008In: 8th International Conference on Physics of Light-Matter Coupling in nanostructures PLMCN8,2008, 2008Conference paper (Other academic)
  • 15.
    Larsson, Arvid
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Moskalenko, Evgeny
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Tuning of the charge state of individual InAs/GaAs quantum dots by an external magnetic field2008In: The 5th International Conference on Semiconductor Quantum Dots QD2008,2008, 2008Conference paper (Other academic)
  • 16.
    Larsson, L. Arvid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Moskalenko, E. S.
    Russian Academy of Science.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Temperature and Magnetic Field Effects on the Transport Controlled Charge State of a Single Quantum Dot2010In: NANOSCALE RESEARCH LETTERS, ISSN 1931-7573, Vol. 5, no 7, p. 1150-1155Article in journal (Refereed)
    Abstract [en]

    Individual InAs/GaAs quantum dots are studied by micro-photoluminescence. By varying the strength of an applied external magnetic field and/or the temperature, it is demonstrated that the charge state of a single quantum dot can be tuned. This tuning effect is shown to be related to the in-plane electron and hole transport, prior to capture into the quantum dot, since the photo-excited carriers are primarily generated in the barrier.

  • 17.
    Larsson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Moskalenko, Evgenii
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Verdozzi, C.
    Solid State Theory, Institute of Physics, Lund University.
    Almbladh, C.-O.
    Solid State Theory, Institute of Physics, Lund University.
    Schoenfeld, W. V.
    Materials Department, University of California, Santa Barbara.
    Petroff, P. M.
    Materials Department, University of California, Santa Barbara.
    Magnetic field effects on optical and transport properties in InAs/GaAs quantum dots2006In: Physical Review B, ISSN 1098-0121, Vol. 74, no 24Article in journal (Refereed)
    Abstract [en]

    A photoluminescence study of self-assembled InAs/GaAs quantum dots under the influence of magnetic fields perpendicular and parallel to the dot layer is presented. At low temperatures, the magnetic field perpendicular to the dot layer alters the in-plane transport properties due to localization of carriers in wetting layer (WL) potential fluctuations. Decreased transport in the WL results in a reduced capture into the quantum dots and consequently a weakened dot-related emission. The effect of the magnetic field exhibits a considerable dot density dependence, which confirms the correlation to the in-plane transport properties. An interesting effect is observed at temperatures above approximately 100  K, for which magnetic fields, both perpendicular and parallel to the dot layer, induced an increment of the quantum dot photoluminescence. This effect is ascribed to the magnetic confinement of the exciton wave function, which increases the probability for carrier capture and localization in the dot, but affects also the radiative recombination with a reduced radiative lifetime in the dots under magnetic compression.

  • 18.
    Lenz, Annika
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Selegård, Linnea
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, Faculty of Science & Engineering.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Ojamäe, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Inorganic Chemistry. Linköping University, The Institute of Technology.
    ZnO Nanoparticles Functionalized with Organic Acids: An Experimental and Quantum-Chemical Study2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 40, p. 17332-17341Article in journal (Refereed)
    Abstract [en]

    Electrochemical synthesis and physical characterization of ZnO nanoparticles functionalized with four different organic acids, three aromatic (benzoic, nicotinic, and trans-cinnamic acid) and one nonaromatic (formic acid), are reported. The functionalized nanoparticles have been characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV−vis, and photoluminescence spectroscopy. The adsorption of the organic acids at ZnO nanoparticles was further analyzed and interpreted using quantum-chemical density-functional theory computations. Successful functionalization of the nanoparticles was confirmed experimentally by the measured splitting of the carboxylic group stretching vibrations as well as by the N(1s) and C(1s) peaks from XPS. From a comparison between computed and experimental IR spectra, a bridging mode adsorption geometry was inferred. PL spectra exhibited a remarkably stronger near band edge emission for nanoparticles functionalized with formic acid as compared to the larger aromatic acids. From the quantum-chemical computations, this was interpreted to be due to the absence of aromatic adsorbate or surface states in the band gap of ZnO, caused by the formation of a complete monolayer of HCOOH. In the UV−vis spectra, strong charge-transfer transitions were observed.

  • 19.
    Moskalenko, Evgenii
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Spin polarization of neutral excitons in quantum dots: the role of the carrier collection area2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, NANOTECHNOLOGY, Vol. 21, no 34Article in journal (Refereed)
    Abstract [en]

    A high degree (approximate to 55%) of circular polarization has been observed for the neutral exciton in InAs/GaAs quantum dots (QDs). The possibility to record non- zero polarization of the neutral exciton is explained in terms of different capture times of the light electron compared with the heavier holes into the QDs from the wetting layer. This interpretation is supported by the progressive reduction of the polarization degree with increasing QD density, and also with increasing temperature.

  • 20.
    Moskalenko, Evgenii
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Spin polarization of the neutral exciton in a single InAs quantum dot at zero magnetic field2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, no 19, p. 193413-Article in journal (Refereed)
    Abstract [en]

    A high degree of spin polarization for the neutral exciton in individual quantum dots, at zero external magnetic field, is monitored. While a high polarization degree is commonly observed for the charged exciton, a negligible polarization has been predicted for the neutral exciton. The exceptionally high polarization (andgt;60%) observed here is explained in terms of a dynamical nuclear polarization field, stabilizing the electron spin. Such polarization of the quantum dot nuclei, in case of the neutral exciton, is possible due to unequal capture time of electrons and holes.

  • 21.
    Moskalenko, Evgenii
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Schoenfeld, W. V.
    Materials Department, University of California, Santa Barbara.
    Petroff, P. M.
    Materials Department, University of California, Santa Barbara.
    Effective tuning of the charge state of a single InAs/GaAs quantum dot by an external magnetic field2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 7, p. 075306-Article in journal (Refereed)
    Abstract [en]

    A microphotoluminescence study of single InAs/GaAs quantum dots (QDs) in the presence of an applied external magnetic field is presented. Attention is focused on the redistribution between the spectral lines of a single QD observed at increasing magnetic field parallel to the growth direction (Faraday geometry). The redistribution effect is explained by considering the electron drift velocity in the QD plane that affects the probability for capture into the QD. In contrast, no redistribution is observed when applying the magnetic field perpendicular to the growth direction (Voigt geometry).

  • 22.
    Moskalenko, Evgenii
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Larsson, Arvid
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Larsson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Schoenfeld, Winston V
    University of California, USA.
    Petroff, Pierre M
    University of California, USA.
    Comparative Magneto-Photoluminescence Study of Ensembles and of Individual InAs Quantum Dots2009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 1, p. 353-359Article in journal (Refereed)
    Abstract [en]

    We report on magneto-photoluminescence studies of InAs/GaAs quantum dots (QDs) of considerably different densities, from dense ensembles down to individual dots. It is found that a magnetic field applied in Faraday geometry decreases the photoluminescence (PL) intensity of OD ensembles, which is not accompanied by the corresponding increase of PL signal of the wetting layer on which ON are grown. The model suggested to explain these data assumes considerably different strengths of suppression of electron and hole fluxes by a magnetic field. This idea has been successfully checked in experiments on individual ON, where the PL spectra allow to directly monitor the charge state of a OD and, hence, to conclude about relative magnitudes of electron and hole fluxes toward the QD. Comparative studies of different individual QDs have revealed that the internal electric field in the sample (which was altered in the experiments in a controllable way) together with an external magnetic field will determine the charge state and emission intensity of the QDs.

  • 23.
    Moskalenko, Evgeny
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Larsson, Arvid
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Larsson, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Holtz, Per-Olof
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Schoenfeld, W.V.
    Petroff, P.M.
    Effective tuning of the charge state of a single InAs/GaAs quantum dot by means of external fields2008In: One Day Quantum Dot Meeting,2008, 2008Conference paper (Other academic)
1 - 23 of 23
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