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Holtz, Per-Olof
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Publications (10 of 238) Show all publications
Chen, Y.-T., Karlsson, K. F., Birch, J. & Holtz, P.-O. (2016). Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy. Scientific Reports, 6(21482), 1-7
Open this publication in new window or tab >>Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy
2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 21482, p. 1-7Article in journal (Refereed) Published
Abstract [en]

Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-125803 (URN)10.1038/srep21482 (DOI)000370040800001 ()26876009 (PubMedID)
Note

Funding Agencies|Knut and Alice Wallenberg Foundation

Available from: 2016-03-08 Created: 2016-03-04 Last updated: 2017-11-30
Sadollah Khani, A., Nour, O., Willander, M., Kazeminezhad, I., Khranovskyy, V., Eriksson, M. O., . . . Holtz, P.-O. (2015). A detailed optical investigation of ZnO@ZnS core-shell nanoparticles and their photocatalytic activity at different pH values. Ceramics International, 41(5), 7174-7184
Open this publication in new window or tab >>A detailed optical investigation of ZnO@ZnS core-shell nanoparticles and their photocatalytic activity at different pH values
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2015 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, no 5, p. 7174-7184Article in journal (Refereed) Published
Abstract [en]

In this study zinc oxide nanoparticles (NPs) were synthesized via a co-precipitation method and were covered by zinc sulfate using a chemical approach at a temperature of 60 degrees C forming ZnO@ZnS core-shell nanoparticles (CSNPs). In order to investigate the effect of the shell thickness on the optical and photocatalytic properties, many samples were grown with different concentration of the sulfur source. The results show that, covering ZnO with ZnS leads to form a type II band alignment system. In addition, the band gap of the ZnO@ZnS CSNPs was found less than both of the core and the shell materials. Also the emission peak intensity of the ZnO NPs changes as a result of manipulating oxygen vacancies via covering. The photocatalytic activity of the ZnO@ZnS CSNPs was invpstigated for degradation of the Congo red dye. As dye pollutants can be found in mediums with different pH, the experiments were performed at three pH values to determine the best photocatalyst for each pH. Congo red dye degradation experiments indicate that the ZnO@ZnS CSNPs act more efficiently as a photcatalyst at pH values of 4 and 7 compare to the pure ZnO NPs.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
A. Chemical preparation; B. Spectroscopy; C. Optical properties; D. ZnO
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-118021 (URN)10.1016/j.ceramint.2015.02.040 (DOI)000353176400070 ()
Note

Funding Agencies|Shahid Chamran University; Linkoping University; Linkoping Linne Initiative

Available from: 2015-05-21 Created: 2015-05-20 Last updated: 2018-02-13
Sodzel, D., Khranovskyy, V., Beni, V., Turner, A. P., Viter, R., Eriksson, M. O., . . . Yakimova, R. (2015). Control of hydrogen peroxide and glucose via UV and Visible Photoluminescence of ZnO nanoparticles.. Microchimica Acta, 182(9-10), 1819-1826
Open this publication in new window or tab >>Control of hydrogen peroxide and glucose via UV and Visible Photoluminescence of ZnO nanoparticles.
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2015 (English)In: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 182, no 9-10, p. 1819-1826Article in journal (Refereed) Published
Abstract [en]

We report on an indirect optical method for the determination of glucose via the detection of hydrogen peroxide (H2O2) that is generated during the glucose oxidase (GOx) catalyzed oxidation of glucose. It is based on the finding that the ultraviolet (~374 nm) and visible (~525 nm) photoluminescence of pristine zinc oxide (ZnO) nanoparticles strongly depends on the concentration of H2O2 in water solution. Photoluminescence is quenched by up to 90 % at a 100 mM level of H2O2. The sensor constructed by immobilizing GOx on ZnO nanoparticles enabled glucose to be continuously monitored in the 10 mM to 130 mM concentration range, and the limit of detection is 10 mM. This enzymatic sensing scheme is supposed to be applicable to monitoring glucose in the food, beverage and fermentation industries. It has a wide scope in that it may be extended to numerous other substrate or enzyme activity assays based on the formation of H2O2, and of assays based on the consumption of H2O2 by peroxidases.

Place, publisher, year, edition, pages
Springer Netherlands, 2015
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-118305 (URN)10.1007/s00604-015-1493-9 (DOI)000356449700030 ()
Available from: 2015-05-26 Created: 2015-05-26 Last updated: 2017-12-04
Jemsson, T., Machhadani, H., Holtz, P.-O. & Karlsson, F. K. (2015). Polarized single photon emission and photon bunching from an InGaN quantum dot on a GaN micropyramid. Nanotechnology, 26(6), 065702
Open this publication in new window or tab >>Polarized single photon emission and photon bunching from an InGaN quantum dot on a GaN micropyramid
2015 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 26, no 6, p. 065702-Article in journal (Refereed) Published
Abstract [en]

We report on excitonic single photon emission and biexcitonic photon bunching from an InGaN quantum dot formed on the apex of a hexagonal GaN micropyramid. An approach to suppress uncorrelated emission from the pyramid base is proposed, a metal lm is demonstrated to eectively screen background emission and thereby signicantly enhance the signal-to-background ratio of the quantum dot emission. As a result, the second order coherence function at zero time delay g(2)(0) is signicantly reduced (to g(2)(0) = 0.24, raw value) for the excitonic autocorrelation at a temperature of 12 K under continuous wave excitation, and a dominating single photon emission is demonstrated to survive up to 50 K. The deterioration of the g(2)(0)-value at elevated temperatures is well understood as the combined eect of reduced signal-to-background ratio and limited time resolution of the setup. This result underlines the great potential of site controlled pyramidal dots as sources of fast polarized single photons.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113347 (URN)10.1088/0957-4484/26/6/065702 (DOI)000348448000018 ()
Available from: 2015-01-16 Created: 2015-01-16 Last updated: 2017-12-05Bibliographically approved
Karlsson, K. F., Oberli, D. Y., Dupertuis, M. A., Troncale, V., Byszewski, M., Pelucchi, E., . . . Kapon, E. (2015). Spectral signatures of high-symmetry quantum dots and effects of symmetry breaking. New Journal of Physics, 17(10)
Open this publication in new window or tab >>Spectral signatures of high-symmetry quantum dots and effects of symmetry breaking
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2015 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 17, no 10Article in journal (Refereed) Published
Abstract [en]

High symmetry epitaxial quantum dots (QDs) with three or more symmetry planes provide a very promising route for the generation of entangled photons for quantum information applications. The great challenge to fabricate nanoscopic high symmetry QDs is further complicated by the lack of structural characterization techniques able to resolve small symmetry breaking. In this work, we present an approach for identifying and analyzing the signatures of symmetry breaking in the optical spectra of QDs. Exciton complexes in InGaAs/AlGaAs QDs grown along the [111]B crystalline axis in inverted tetrahedral pyramids are studied by polarization resolved photoluminescence spectroscopy combined with lattice temperature dependence, excitation power dependence and temporal photon correlation measurements. By combining such a systematic experimental approach with a simple theoretical approach based on a point-group symmetry analysis of the polarized emission patterns of each exciton complex, we demonstrate that it is possible to achieve a strict and coherent identification of all the observable spectral patterns of numerous exciton complexes and a quantitative determination of the fine structure splittings of their quantum states. This analysis is found to be particularly powerful for selecting QDs with the highest degree of symmetry ( C 3 v and ##IMG## [http://ej.iop.org/images/1367-2630/17/10/103017/njp519062ieqn1.gif] $D_3h$ ) for potential applications of these QDs as polarization entangled photon sources. We exhibit the optical spectra when evolving towards asymmetrical QDs, and show the higher sensitivity of certain exciton complexes to symmetry breaking.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-123949 (URN)10.1088/1367-2630/17/10/103017 (DOI)000367329000006 ()
Note

Funding agencies: Swiss National Science Foundation; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]

Available from: 2016-01-14 Created: 2016-01-14 Last updated: 2017-11-30Bibliographically approved
Zhou, S., Liu, Y., Wang, D., Yu, Z., Zhao, W., Le, L. & Holtz, P.-O. (2015). The calculation of InGaN quantum dot formation mechanism on GaN pyramid. Superlattices and Microstructures, 84, 72-79
Open this publication in new window or tab >>The calculation of InGaN quantum dot formation mechanism on GaN pyramid
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2015 (English)In: Superlattices and Microstructures, ISSN 0749-6036, E-ISSN 1096-3677, Vol. 84, p. 72-79Article in journal (Refereed) Published
Abstract [en]

An equilibrium approach is used to calculate the free energy and composition distribution of InGaN/GaN quantum dot located on the InGaN/GaN pyramid. The energy balance method is adopted to predict critical conditions for quantum dot formation. We find that the formation of QD depends strongly on the size of pyramid top surface. The results can fit our experiment qualitatively.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
InGaN quantum dots; GaN pyramid; Critical diameter
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-120267 (URN)10.1016/j.spmi.2015.03.067 (DOI)000357227900008 ()
Note

Funding Agencies|National Natural Science Foundation of China [61275201, 61372037]; Program for New Century Excellent Talents in University of Ministry of Education of China [NCET-10-0261]; Fund of State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), P.R. China; Fundamental Research Funds for the Central Universities of Ministry of Education of China [2011RC0402]; Research Fund for the Doctoral Program of Higher Education of China [20100005110013]; Opened Fund of the State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences

Available from: 2015-07-24 Created: 2015-07-24 Last updated: 2017-12-04
Klangtakai, P., Sanorpim, S., Karlsson, F., Holtz, P.-O., Pimanpang, S. & Onabe, K. (2014). Anomalous excitation-power-dependent photoluminescence of InGaAsN/GaAs T-shaped quantum wire. Physica Status Solidi (a) applications and materials science, 211(8), 1740-1744
Open this publication in new window or tab >>Anomalous excitation-power-dependent photoluminescence of InGaAsN/GaAs T-shaped quantum wire
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2014 (English)In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 211, no 8, p. 1740-1744Article in journal (Refereed) Published
Abstract [en]

The selected InGaAsN/GaAs T-shaped quantum wire (T-QWR) fabricated by metal organic vapor phase epitaxy has been investigated by microphotoluminescence (m-PL) and excitation-power-dependent mu-PL. The optical characteristics of one-dimensional structure were taken at low-temperature (4 K) and room temperature (RT) to clarify the intersection of two familiar quantum wells (QWs) in the [001] and [110] directions, named QW1 and QW2, respectively. For the excitation-power-dependent measurement, the intensity of the excitation source was used in the range of 0.001I(0) to I-0. The result shows that all of emissions related to QW1 and QWR peaks have a nonsymmetric line shape as evidenced by the tailing on the lower-energy side. All peaks shift to higher-energy side (blueshift) with the increase of the excitation power intensity. The blueshift and the low-energy tailing of PL peaks are attributed to the alloying effect. However, the emission peak related to QWR region shows a larger blueshift rate than that of QW1 on increasing of the excitation power intensity. This is an anomalous characteristic for the low-dimensional structure, affected by the large fluctuation state in the QWR region. This fluctuation state is combined of both edges of QWs (QW1 and QW2).

Place, publisher, year, edition, pages
Wiley-VCH Verlag, 2014
Keyword
GaAs; InGaAsN; MOVPE; photoluminescence; quantum wires
National Category
Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-110487 (URN)10.1002/pssa.201330543 (DOI)000340521000010 ()
Note

Funding Agencies|Institute for Promotion of Teaching Science and Technology (IPST); National Nanotechnology Center (NANOTEC), NSTDA, Ministry of Science and Technology, Thailand, through its program of Center of Excellence Network; Thailand Research Fund [TRG5280030]; Thai Government Stimulus Package 2 under the project for Establishment of Comprehensive Center for Innovative Food, Health Products and Agriculture [TKK2555]

Available from: 2014-09-15 Created: 2014-09-12 Last updated: 2017-12-05
Khranovskyy, V., Eriksson, M. O., Radnóczi, G. Z., Khalid, A., Zhang, H., Holtz, P.-O., . . . Yakimova, R. (2014). Correction: Photoluminescence study of basal plane stacking faults in ZnO nanowires (vol 4639, pg 50, 2014). Physica. B, Condensed matter, 454, 279-279
Open this publication in new window or tab >>Correction: Photoluminescence study of basal plane stacking faults in ZnO nanowires (vol 4639, pg 50, 2014)
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2014 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 454, p. 279-279Article in journal (Other academic) Published
Abstract [en]

n/a

Place, publisher, year, edition, pages
Elsevier, 2014
National Category
Chemical Sciences Physical Sciences
Identifiers
urn:nbn:se:liu:diva-112032 (URN)10.1016/j.physb.2014.08.001 (DOI)000342682100045 ()
Available from: 2014-11-17 Created: 2014-11-13 Last updated: 2017-12-05Bibliographically approved
Lundskog, A., Hsu, C.-W., Karlsson, K. F., Amloy, S., Nilsson, D., Forsberg, U., . . . Janzén, E. (2014). Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots. Light: Science & Applications, 3, Article ID e139.
Open this publication in new window or tab >>Direct generation of linearly-polarized photon emission with designated orientations from site-controlled InGaN quantum dots
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2014 (English)In: Light: Science & Applications, ISSN 2095-5545, Vol. 3, article id e139Article in journal (Refereed) Published
Abstract [en]

Semiconductor quantum dots (QDs) have been demonstrated viable for the emission of single photons on demand during the past decade. However, the synthesis of QDs emitting photons with pre-defined and deterministic polarization vectors has proven arduous. The access of linearly-polarized photons is essential for various applications. In this report, a novel concept to directly generate linearly-polarized photons is presented. This concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids, by which predefined orientations herald the polarization vectors of the emitted photons from the QDs. This growth scheme should allow fabrication of ultracompact arrays of photon emitters, with a controlled polarization direction for each individual QD emitter.

Place, publisher, year, edition, pages
Nature Publishing Group, 2014
Keyword
GaN; InGaN; photoluminescence; polarized emission; quantum dot
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-97417 (URN)10.1038/lsa.2014.20 (DOI)000331998400011 ()
Available from: 2013-09-12 Created: 2013-09-12 Last updated: 2017-04-11Bibliographically approved
Amloy, S., Karlsson, K. F., Eriksson, M. O., Palisaitis, J., Persson, P. O. Å., Chen, Y. T., . . . Holtz, P.-O. (2014). Excitons and biexcitons in InGaN quantum dot like localization centers. Nanotechnology, 25(49), 495702
Open this publication in new window or tab >>Excitons and biexcitons in InGaN quantum dot like localization centers
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2014 (English)In: Nanotechnology, ISSN 0957-4484, Vol. 25, no 49, p. 495702-Article in journal (Refereed) Published
Abstract [en]

Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross-section transmission electron microscopy reveals varying shapes and lateral sizes in the range ∼1–5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to −22 meV, in correlation with the exciton emission energy. Negative binding energies are only justified by a three-dimensional quantum confinement, which confirms QD-like properties of the localization centers. The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ∼3 nm for a QD with strongly negative Ebxx = −15.5 meV. 

Place, publisher, year, edition, pages
IOP Publishing, 2014
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-113334 (URN)10.1088/0957-4484/25/49/495702 (DOI)000345603800018 ()25410551 (PubMedID)
Available from: 2015-01-16 Created: 2015-01-16 Last updated: 2018-03-08
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