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Sadowski J, Kaleta A, Kryvyi S, Janaszko D, Kurowska B, Bilska M, Wojciechowski T, Domagala JZ, Sanchez AM, Kret S. Bi incorporation and segregation in the MBE-grown GaAs-(Ga,Al)As-Ga(As,Bi) core-shell nanowires. Sci Rep 2022; 12:6007. [PMID: 35397635 PMCID: PMC8994761 DOI: 10.1038/s41598-022-09847-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2021] [Accepted: 03/29/2022] [Indexed: 11/09/2022] Open
Abstract
Incorporation of Bi into GaAs-(Ga,Al)As-Ga(As,Bi) core-shell nanowires grown by molecular beam epitaxy is studied with transmission electron microscopy. Nanowires are grown on GaAs(111)B substrates with Au-droplet assisted mode. Bi-doped shells are grown at low temperature (300 °C) with a close to stoichiometric Ga/As flux ratio. At low Bi fluxes, the Ga(As,Bi) shells are smooth, with Bi completely incorporated into the shells. Higher Bi fluxes (Bi/As flux ratio ~ 4%) led to partial segregation of Bi as droplets on the nanowires sidewalls, preferentially located at the nanowire segments with wurtzite structure. We demonstrate that such Bi droplets on the sidewalls act as catalysts for the growth of branches perpendicular to the GaAs trunks. Due to the tunability between zinc-blende and wurtzite polytypes by changing the nanowire growth conditions, this effect enables fabrication of branched nanowire architectures with branches generated from selected (wurtzite) nanowire segments.
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Affiliation(s)
- Janusz Sadowski
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland. .,Department of Physics and Electrical Engineering, Linnaeus University, 39182, Kalmar, Sweden.
| | - Anna Kaleta
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Serhii Kryvyi
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Dorota Janaszko
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Bogusława Kurowska
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Marta Bilska
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Tomasz Wojciechowski
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland.,International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Jarosław Z Domagala
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland
| | - Ana M Sanchez
- Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
| | - Sławomir Kret
- Institute of Physics Polish Academy of Sciences, Aleja Lotnikow 32/46, 02668, Warsaw, Poland.
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Spin-Current Oscillations in Diluted Magnetic Semiconductor Multibarrier GaMnAs/GaAs: Role of Temperature and Bias Voltage. COATINGS 2022. [DOI: 10.3390/coatings12040504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
This paper has studied the electronic properties of multi-diluted magnetic semiconductor (DMS) layers Ga(1 − x)MnxAs interposed between nonmagnetic GaAs layers. The asymmetry of confining potential on the transmission coefficient by tuning the temperature and the size of the (DMS) layers was discussed. The diluted magnetic layers Ga(1 − x)MnxAs behave as barriers for spin-up holes and quantum wells for spin-down holes. Furthermore, we have addressed the impact of an applied bias voltage and the temperature on the variation of the spin-polarization and spin current densities. Our findings reveal that the transmission coefficients present an oscillating behavior due to the resonant states and strongly depend on the temperature of the system and the number of magnetic layers. Furthermore, the obtained results demonstrated that the number of these states is multiplied by augmenting the magnetic layers. Moreover, we demonstrate that the asymmetric structure presents a completely different transmission of holes than the symmetric structure. Furthermore, the negative differential resistance (NDR) is demonstrated in the current density variations. Especially, this (NDR) was more intense for spin-up holes than spin-down holes. The findings in the present paper can be useful in manufacturing spin-filters by adjusting the values of the temperature and the external voltages.
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Gas K, Kret S, Zaleszczyk W, Kamińska E, Sawicki M, Wojtowicz T, Szuszkiewicz W. Oxidation of MBE-Grown ZnTe and ZnTe/Zn Nanowires and Their Structural Properties. MATERIALS 2021; 14:ma14185252. [PMID: 34576476 PMCID: PMC8469095 DOI: 10.3390/ma14185252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 09/01/2021] [Accepted: 09/07/2021] [Indexed: 12/23/2022]
Abstract
Results of comparative structural characterization of bare and Zn-covered ZnTe nanowires (NWs) before and after thermal oxidation at 300 °C are presented. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, and Raman scattering not only unambiguously confirm the conversion of the outer layer of the NWs into ZnO, but also demonstrate the influence of the oxidation process on the structure of the inner part of the NWs. Our study shows that the morphology of the resulting ZnO can be improved by the deposition of thin Zn shells on the bare ZnTe NWs prior to the oxidation. The oxidation of bare ZnTe NWs results in the formation of separated ZnO nanocrystals which decorate crystalline Te cores of the NWs. In the case of Zn-covered NWs, uniform ZnO shells are formed, however they are of a fine-crystalline structure or partially amorphous. Our study provides an important insight into the details of the oxidation processes of ZnTe nanostructures, which could be of importance for the preparation and performance of ZnTe based nano-devices operating under normal atmospheric conditions and at elevated temperatures.
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Affiliation(s)
- Katarzyna Gas
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland; (S.K.); (W.Z.); (M.S.); (W.S.)
- Correspondence:
| | - Slawomir Kret
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland; (S.K.); (W.Z.); (M.S.); (W.S.)
| | - Wojciech Zaleszczyk
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland; (S.K.); (W.Z.); (M.S.); (W.S.)
- International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland;
| | - Eliana Kamińska
- Institute of High Pressure Physics Unipress, Al. Prymasa Tysiaclecia 98, PL-01142 Warsaw, Poland;
| | - Maciej Sawicki
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland; (S.K.); (W.Z.); (M.S.); (W.S.)
| | - Tomasz Wojtowicz
- International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland;
| | - Wojciech Szuszkiewicz
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland; (S.K.); (W.Z.); (M.S.); (W.S.)
- Institute of Physics, College of Natural Sciences, University of Rzeszow, S. Pigonia 1, PL-35310 Rzeszow, Poland
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Wang L, Zhang Y, Liu T, Zhang Z, Hu H, Zou J, Jia Q, Jiang Z. Ge xSi 1-x virtual-layer enhanced ferromagnetism in self-assembled Mn 0.06Ge 0.94 quantum dots grown on Si wafers by molecular beam epitaxy. NANOSCALE 2020; 12:3997-4004. [PMID: 32016234 DOI: 10.1039/c9nr09315j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Self-assembled Mn0.06Ge0.94 quantum dots (QDs) on a Si substrate or GexSi1-x virtual substrate (VS) were grown by molecular beam epitaxy. The GexSi1-x VS of different thicknesses and Ge compositions x were utilized to modulate the ferromagnetic properties of the above QDs. The MnGe QDs on GexSi1-x VS show a significantly enhanced ferromagnetism with a Curie temperature above 220 K. On the basis of the microstructural and magnetization results, the ferromagnetic properties of the QDs on GexSi1-x VS are believed to come from the intrinsic MnGe ferromagnetic phase rather than any intermetallic ferromagnetic compounds of Mn and Ge. At the same time, we found that by increasing the Ge composition x of GexSi1-x VS, the ferromagnetism of QDs grown on VS will markedly increase due to the improvements of hole concentration and Ge composition inside the QDs. These results are fundamentally important in the understanding and especially in the realization of high Curie temperature MnGe diluted magnetic semiconductors.
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Affiliation(s)
- Liming Wang
- State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, China.
| | - Yichi Zhang
- State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, China.
| | - Tao Liu
- State Key Laboratory of Surface Physics, Department of Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China.
| | - Zhi Zhang
- Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, QLD 4072, Australia
| | - Huiyong Hu
- State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology, School of Microelectronics, Xidian University, Xi'an 710071, China.
| | - Jin Zou
- Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, QLD 4072, Australia
| | - Quanjie Jia
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Beijing 100039, China
| | - Zuimin Jiang
- State Key Laboratory of Surface Physics, Department of Physics, and Collaborative Innovation Center of Advanced Microstructures, Fudan University, Shanghai 200433, China.
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Kaleta A, Kret S, Gas K, Kurowska B, Kryvyi SB, Rutkowski B, Szwacki NG, Sawicki M, Sadowski J. Enhanced Ferromagnetism in Cylindrically Confined MnAs Nanocrystals Embedded in Wurtzite GaAs Nanowire Shells. NANO LETTERS 2019; 19:7324-7333. [PMID: 31500416 DOI: 10.1021/acs.nanolett.9b02956] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Nearly a 30% increase in the ferromagnetic phase transition temperature has been achieved in strained MnAs nanocrystals embedded in a wurtzite GaAs matrix. Wurtzite GaAs exerts tensile stress on hexagonal MnAs nanocrystals, preventing a hexagonal to orthorhombic structural phase transition, which in bulk MnAs is combined with the magnetic one. This effect results in a remarkable shift of the magneto-structural phase transition temperature from 313 K in the bulk MnAs to above 400 K in the tensely strained MnAs nanocrystals. This finding is corroborated by the state of the art transmission electron microscopy, sensitive magnetometry, and the first-principles calculations. The effect relies on defining a nanotube geometry of molecular beam epitaxy grown core-multishell wurtzite (Ga,In)As/(Ga,Al)As/(Ga,Mn)As/GaAs nanowires, where the MnAs nanocrystals are formed during the thermal-treatment-induced phase separation of wurtzite (Ga,Mn)As into the GaAs-MnAs granular system. Such a unique combination of two types of hexagonal lattices provides a possibility of attaining quasi-hydrostatic tensile strain in MnAs (impossible otherwise), leading to the substantial ferromagnetic phase transition temperature increase in this compound.
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Affiliation(s)
- Anna Kaleta
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
| | - Slawomir Kret
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
| | - Katarzyna Gas
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
| | - Boguslawa Kurowska
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
| | - Serhii B Kryvyi
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
| | - Bogdan Rutkowski
- Faculty of Metals Engineering and Industrial Computer Science , AGH University of Science and Technology , Aleja A. Mickiewicza 30 , 30-059 Kraków , Poland
| | - Nevill Gonzalez Szwacki
- Institute of Theoretical Physics, Faculty of Physics , University of Warsaw , Pasteura 5 , 02-093 Warszawa , Poland
| | - Maciej Sawicki
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
| | - Janusz Sadowski
- Institute of Physics , Polish Academy of Sciences , Aleja Lotnikow 32/46 , PL-02-668 Warszawa , Poland
- Department of Physics and Electrical Engineering , Linnaeus University , SE-391 82 Kalmar , Sweden
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Yuan Y, Wang M, Xu C, Hübner R, Böttger R, Jakiela R, Helm M, Sawicki M, Zhou S. Electronic phase separation in insulating (Ga, Mn) As with low compensation: super-paramagnetism and hopping conduction. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:095801. [PMID: 29355839 DOI: 10.1088/1361-648x/aaa9a7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is obtained by ion implantation combined with pulsed laser melting. The sample shows variable-range hopping transport behavior with a Coulomb gap in the vicinity of the Fermi energy, and the activation energy is reduced by an external magnetic field. A blocking super-paramagnetism is observed rather than ferromagnetism. Below the blocking temperature, the sample exhibits a colossal negative magnetoresistance. Our studies confirm that the disorder-induced electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration in the insulator-metal transition regime, and it can account for the observed superparamagnetism and the colossal magnetoresistance.
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Affiliation(s)
- Ye Yuan
- Helmholtz-Zentrum Dresden Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstrasse 400, D-01328 Dresden, Germany. Technische Universität Dresden, D-01062 Dresden, Germany
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Sadowski J, Kret S, Šiušys A, Wojciechowski T, Gas K, Islam MF, Canali CM, Sawicki M. Wurtzite (Ga,Mn)As nanowire shells with ferromagnetic properties. NANOSCALE 2017; 9:2129-2137. [PMID: 28120988 DOI: 10.1039/c6nr08070g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
(Ga,Mn)As having a wurtzite crystal structure was coherently grown by molecular beam epitaxy on the {1100} side facets of wurtzite (Ga,In)As nanowires and further encapsulated by (Ga,Al)As and low temperature GaAs. For the first time, a truly long-range ferromagnetic magnetic order is observed in non-planar (Ga,Mn)As, which is attributed to a more effective hole confinement in the shell containing Mn by the proper selection/choice of both the core and outer shell materials.
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Affiliation(s)
- J Sadowski
- MAX-IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund, Sweden. and Department of Physics and Electrical Engineering, Linnaeus University, SE-391 82 Kalmar, Sweden and Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
| | - S Kret
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
| | - A Šiušys
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
| | - T Wojciechowski
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
| | - K Gas
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
| | - M F Islam
- Department of Physics and Electrical Engineering, Linnaeus University, SE-391 82 Kalmar, Sweden
| | - C M Canali
- Department of Physics and Electrical Engineering, Linnaeus University, SE-391 82 Kalmar, Sweden
| | - M Sawicki
- Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02-668 Warsaw, Poland
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Szymura M, Wojnar P, Kłopotowski Ł, Suffczyński J, Goryca M, Smoleński T, Kossacki P, Zaleszczyk W, Wojciechowski T, Karczewski G, Wojtowicz T, Kossut J. Spin splitting anisotropy in single diluted magnetic nanowire heterostructures. NANO LETTERS 2015; 15:1972-1978. [PMID: 25710186 DOI: 10.1021/nl504853m] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We study the impact of the nanowire shape anisotropy on the spin splitting of excitonic photoluminescence. The experiments are performed on individual ZnMnTe/ZnMgTe core/shell nanowires as well as on ZnTe/ZnMgTe core/shell nanowires containing optically active magnetic CdMnTe insertions. When the magnetic field is oriented parallel to the nanowire axis, the spin splitting is several times larger than for the perpendicular field. We interpret this pronounced anisotropy as an effect of mixing of valence band states arising from the strain present in the core/shell geometry. This interpretation is further supported by theoretical calculations which allow to reproduce experimental results.
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Affiliation(s)
- Małgorzata Szymura
- Institute of Physics, Polish Academy of Sciences , Al Lotników 32/46, PL-02-668 Warsaw, Poland
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