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Lu, Jun
Publications (10 of 120) Show all publications
Junaid, M., Hsiao, C.-L., Chen, Y.-T., Lu, J., Palisaitis, J., Persson, P. O., . . . Birch, J. (2018). Effects of N2 Partial Pressure on Growth, Structure, and Optical Properties of GaN Nanorods Deposited by Liquid-Target Reactive Magnetron Sputter Epitaxy. Nanomaterials, 8(4), Article ID 223.
Open this publication in new window or tab >>Effects of N2 Partial Pressure on Growth, Structure, and Optical Properties of GaN Nanorods Deposited by Liquid-Target Reactive Magnetron Sputter Epitaxy
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2018 (English)In: Nanomaterials, ISSN 2079-4991, Vol. 8, no 4, article id 223Article in journal (Other academic) Published
Abstract [en]

GaN nanorods, essentially free from crystal defects and exhibiting very sharp band-edge luminescence, have been grown by reactive direct-current magnetron sputter epitaxy onto Si (111) substrates at a low working pressure of 5 mTorr. Upon diluting the reactive N2 working gas with a small amount of Ar (0.5 mTorr), we observed an increase in the nanorod aspect ratio from 8 to ~35, a decrease in the average diameter from 74 to 35 nm, and a two-fold increase in nanorod density. With further dilution (Ar = 2.5 mTorr), the aspect ratio decreased to 14, while the diameter increased to 60 nm and the nanorod density increased to a maximum of 2.4 × 109 cm−2. Yet, lower N2 partial pressures eventually led to the growth of continuous GaN films. The observed morphological dependence on N2 partial pressure is explained by a change from N-rich to Ga-rich growth conditions, combined with reduced GaN-poisoning of the Ga-target as the N2 gas pressure is reduced. Nanorods grown at 2.5 mTorr N2 partial pressure exhibited a high intensity 4 K photoluminescence neutral donor bound exciton transitions (D0XA) peak at ~3.479 eV with a full-width-at-half-maximum of 1.7 meV. High-resolution transmission electron microscopy corroborated the excellent crystalline quality of the nanorods.

Place, publisher, year, edition, pages
Basel, Switzerland: MDPI, 2018
Keywords
GaN, nanorods, X-ray diffraction, TEM, photoluminescence, magnetron sputter epitaxy, sputtering
National Category
Condensed Matter Physics Nano Technology
Identifiers
urn:nbn:se:liu:diva-84654 (URN)10.3390/nano8040223 (DOI)000434889100044 ()
Note

Funding agencies: Swedish Research Council (VR) [621-2013-5360, 621-2012-4420, 2016-04412]; Swedish Government Strategic Research Area Grant in Materials Science AFM-SFO MatLiU [2009-00971]; Knut and Alice Wallenberg Foundation

Available from: 2018-04-09 Created: 2012-10-16 Last updated: 2018-06-28Bibliographically approved
Halim, J., Palisaitis, J., Lu, J., Thörnberg, J., E. J., M., M., P., . . . Rosén, J. (2018). Synthesis of Two-Dimensional Nb1.33C (MXene) with Randomly Distributed Vacancies by Etching of the Quaternary Solid Solution (Nb2/3Sc1/3)2AlC MAX Phase. ACS Applied Nano Materials, 1(6), 2455-2460
Open this publication in new window or tab >>Synthesis of Two-Dimensional Nb1.33C (MXene) with Randomly Distributed Vacancies by Etching of the Quaternary Solid Solution (Nb2/3Sc1/3)2AlC MAX Phase
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2018 (English)In: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 1, no 6, p. 2455-2460Article in journal (Refereed) Published
Abstract [en]

Introducing point defects in two-dimensional (2D) materials can alter or enhance their properties. Here, we demonstrate how etching a laminated (Nb2/3Sc1/3)2AlC MAX phase (solid solution) of both the Sc and Al atoms results in a 2D Nb1.33C material (MXene) with a large number of vacancies and vacancy clusters. This method is applicable to any quaternary, or higher, MAX phase, wherein one of the transition metals is more reactive than the other and could be of vital importance in applications such as catalysis and energy storage. We also report, for the first time, on the existence of solid solution (Nb2/3Sc1/3)3AlC2 and (Nb2/3Sc1/3)4AlC3 phases.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
2D material; electronic properties; MXene; synthesis; transition-metal carbide
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-151667 (URN)10.1021/acsanm.8b00332 (DOI)
Available from: 2018-09-28 Created: 2018-09-28 Last updated: 2018-10-09Bibliographically approved
Kerdsongpanya, S., Eriksson, F., Jensen, J., Lu, J., Sun, B., Kan Koh, Y., . . . Eklund, P. (2016). Experimental and Theoretical Investigation of Cr1-xScxN Solid Solutions for Thermoelectric Applications. Journal of Applied Physics, 120(21), Article ID 215103.
Open this publication in new window or tab >>Experimental and Theoretical Investigation of Cr1-xScxN Solid Solutions for Thermoelectric Applications
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2016 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, no 21, article id 215103Article in journal (Refereed) Published
Abstract [en]

We investigate the trends in mixing thermodynamics of Cr1-xScxN solid solutions in the cubic B1 structure and their electronic density of state by first-principle calculations, and thin-film synthesis of Cr1-xScxN solid solutions by reactive dc magnetron sputtering. Films with the composition Cr0.92Sc0.08N exhibit a thermoelectric power factor of about 8x10-4 Wm-1K-2at 770 K, similar to CrN. The results show that the disordered Cr1-xScxN solid solutions is thermodynamically stable in B1 solid solutions at T = 800°C rather than in the B1- L11 ordered solid solutions stable at 0 K. The calculated electronic density of state (DOS) indicates a positive bowing parameter for the electronic band gap of Cr1-xScxN solid solutions. The calculated DOS suggest possible improvement of power factor due to Sc 3d orbital delocalization on Cr 3d orbital gives decreasing electrical resistivity with retained Seebeck coefficient in Cr-rich regime, consistent with the experimentally observed high power factor for the solid solution.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
Keywords
Chromium nitride, Scandium nitride, Thermoelectrics, First-principles calculations, Solid solutions
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-117757 (URN)10.1063/1.4968570 (DOI)000390602600026 ()
Note

Funding agencies: European Research Council under the European Communitys Seventh Framework Programme [335383]; Swedish Research Council (VR) [621-2012-4430, 621-2011-4417, 330-2014-6336]; Marie Sklodowska Curie Actions [INCA 60098]; Linnaeus Strong Research Environment Li

Available from: 2015-05-08 Created: 2015-05-08 Last updated: 2017-12-04Bibliographically approved
Tengdelius, L., Broitman, E., Lu, J., Eriksson, F., Birch, J., Nyberg, T., . . . Högberg, H. (2016). Hard and elastic epitaxial ZrB2 thin films on Al2O3(0001) substrates deposited by magnetron sputtering from a ZrB2 compound target. Acta Materialia, 111, 166-172
Open this publication in new window or tab >>Hard and elastic epitaxial ZrB2 thin films on Al2O3(0001) substrates deposited by magnetron sputtering from a ZrB2 compound target
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2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 111, p. 166-172Article in journal (Refereed) Published
Abstract [en]

Zirconium diboride (ZrB2) exhibits high hardness and high melting point, which is beneficial for applications in for e.g. metal cutting. However, there is limited data on the mechanical properties of ZrB2 films and no data on epitaxial films. In this study, ZrB2(0001) thin films, with thicknesses up to 1.2 μm, have been deposited on Al2O3(0001) substrates by direct current magnetron sputtering from a compound target. X-ray diffraction and transmission electron microscopy show that the films grow epitaxially with two domain types exhibiting different in-plane epitaxial relationships to the substrate. The out-of-plane epitaxial relationship was determined to ZrB2(0001)|Al2O3(0001) and the in-plane relationships of the two domains to ZrB2[100]‖Al2O3[100] and ZrB2[110]‖Al2O3[100]. Mechanical properties of the films, evaluated by nanoindentation, showed that all films exhibit hardness values above 45 GPa, a reduced Young's modulus in the range 350–400 GPa, and a high elastic recovery of 70% at an applied load of 9000 μN.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Borides, Epitaxial growth, Mechanical properties, Nanoindentation, Sputter deposition
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-128612 (URN)10.1016/j.actamat.2016.03.064 (DOI)000375812100018 ()
Note

Funding agencies: Swedish Research Council (VR) [621-2010-3921]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; Knut and Alice Wallenberg Foundation

Available from: 2016-05-25 Created: 2016-05-25 Last updated: 2017-11-30Bibliographically approved
Broitman, E., Tengdelius, L., Hangen, U. D., Lu, J., Hultman, L. & Högberg, H. (2016). High-temperature nanoindentation of epitaxial ZrB2 thin films. Scripta Materialia, 124, 117-120
Open this publication in new window or tab >>High-temperature nanoindentation of epitaxial ZrB2 thin films
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2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 124, p. 117-120Article in journal (Refereed) Published
Abstract [en]

We use in-situ heated nanoindentation to investigate the high-temperature nanomechanical properties of epitaxial and textured ZrB2 films deposited by magnetron sputtering. Epitaxial films deposited on 4H-SiC(0001) show a hardness decrease from 47 GPa at room temperature to 33 GPa at 600 °C, while the reduced elastic modulus does not change significantly. High resolution electron microscopy (HRTEM) with selected area electron diffraction of the indented area in a 0001-textured film reveals a retained continuous ZrB2 film and no sign of crystalline phase transformation, despite massive deformation of the Si substrate. HRTEM analysis supports the high elastic recovery of 96% in the films.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Sputtering; Borides; Ceramic thin film; Nanoindentation; Transmission electron microscopy
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-130917 (URN)10.1016/j.scriptamat.2016.06.033 (DOI)000383294200027 ()
Note

Funding agencies: Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish Research Council (VR) [621-2010-3921]

Available from: 2016-08-31 Created: 2016-08-31 Last updated: 2017-11-21Bibliographically approved
Greczynski, G., Lu, J., Tengstrand, O., Petrov, I., Greene, J. E. & Hultman, L. (2016). Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity. Scripta Materialia, 122, 40-44
Open this publication in new window or tab >>Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity
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2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 122, p. 40-44Article in journal (Refereed) Published
Abstract [en]

We report the first results on nanostructured N-doped bcc-Cr films exhibiting the unique combination of ceramic hardness with metallic toughness and electrical conductivity at unexpectedly low N concentrations, ~ 5 at.%. The Cr:N films are deposited at 200 C in N2/Ar mixtures by high-power pulsed magnetron sputtering using tunable time-domain control of Cr+ and Cr2+ ion fluxes incident at the film growth surface. Subplanted N atoms impede annealing of metal-ion induced point defects and hinder bcc-Cr grain growth, resulting in a material with a nearly isotropic nanostructure and atomically smooth surface, rather than typical Cr:N solid solutions consisting of faceted microcolumns. © 2016 Elsevier Ltd.

Place, publisher, year, edition, pages
Elsevier Ltd, 2016
Keywords
CrN, HIPIMS, Ion mass spectrometry, Magnetron sputtering, Resistivity, Thin films, Toughness, Transition-metal nitrides
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-129248 (URN)10.1016/j.scriptamat.2016.05.011 (DOI)2-s2.0-84971328580 (Scopus ID)
Note

Funding Agencies|#2011.0143, Swedish Research Council; 2013-4018, Swedish Research Council; 2014-5790, Swedish Research Council

Available from: 2016-06-14 Created: 2016-06-14 Last updated: 2017-11-28
Lu, J., Hultman, L., Holmstrom, E., Antonsson, K. H., Grehk, M., Li, W., . . . Golpayegani, A. (2016). Stacking fault energies in austenitic stainless steels. Acta Materialia, 111, 39-46
Open this publication in new window or tab >>Stacking fault energies in austenitic stainless steels
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2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 111, p. 39-46Article in journal (Refereed) Published
Abstract [en]

We measure the stacking fault energy of a set of 20 at% Cr-austenitic stainless steels by means of transmission electron microscopy using the weak beam dark field imaging technique and the isolated dislocations method. The measurements are analyzed together with first principles calculations. The results show that experiment and theory agree very well for the investigated concentration range of Mn (0-8%) and Ni (11-30%). The calculations show that simultaneous relaxation of atomic and spin degrees of freedom is important in order to find the, global energy minimum for these materials. Our results clearly show the great potential of the weak beam dark field technique to obtain accurate measurements of the stacking fault energy of austenitic steels and that the reliable predictability of first principles calculations can be used to design new steels with optimized mechanical properties. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Stacking fault energy; Austenitic steel; Plasticity; Transmission electron microscopy; Density functional theory
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-128922 (URN)10.1016/j.actamat.2016.03.042 (DOI)000375812100005 ()
Note

Funding Agencies|Swedish Research Council Linkoping Linnaeus Initiative LiLi-NFM [2008-6572]; Swedish Government Strategic Faculty Grant in Materials Science at Linkoping University (SFO Mat-LiU/AFM); Sandvik AB; Swedish Research Council; Swedish Foundation for Strategic Research; Chinese Scholarship Council; Knut and Alice Wallenberg Foundation

Available from: 2016-06-09 Created: 2016-06-07 Last updated: 2017-11-30
Kota, S., Zapata-Solvas, E., Ly, A., Lu, J., Elkassabany, O., Huon, A., . . . Barsoum, M. W. (2016). Synthesis and Characterization of an Alumina Forming Nanolaminated Boride: MoAlB. Scientific Reports, 6(26475)
Open this publication in new window or tab >>Synthesis and Characterization of an Alumina Forming Nanolaminated Boride: MoAlB
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2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, no 26475Article in journal (Refereed) Published
Abstract [en]

The MAlB phases are nanolaminated, ternary transition metal borides that consist of a transition metal boride sublattice interleaved by monolayers or bilayers of pure aluminum. However, their synthesis and properties remain largely unexplored. Herein, we synthesized dense, predominantly single-phase samples of one such compound, MoAlB, using a reactive hot pressing method. High-resolution scanning transmission electron microscopy confirmed the presence of two Al layers in between a Mo-B sublattice. Unique among the transition metal borides, MoAlB forms a dense, mostly amorphous, alumina scale when heated in air. Like other alumina formers, the oxidation kinetics follow a cubic time-dependence. At room temperature, its resistivity is low (0.36-0.49 mu Omega m) and - like a metal - drops linearly with decreasing temperatures. It is also a good thermal conductor (35 Wm(-1)K(-1) at 26 degrees C). In the 25-1300 degrees C temperature range, its thermal expansion coefficient is 9.5 x 10(-6) K-1. Preliminary results suggest the compound is stable to at least 1400 degrees C in inert atmospheres. Moderately low Vickers hardness values of 10.6 +/- 0.3 GPa, compared to other transition metal borides, and ultimate compressive strengths up to 1940 +/- 103 MPa were measured at room temperature. These results are encouraging and warrant further study of this compound for potential use at high temperatures.

Place, publisher, year, edition, pages
NATURE PUBLISHING GROUP, 2016
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-129491 (URN)10.1038/srep26475 (DOI)000376491700001 ()27220751 (PubMedID)
Note

Funding Agencies|Leverhulme Trust; Army Research Office [W911NF-11-1-0525]

Available from: 2016-06-21 Created: 2016-06-20 Last updated: 2017-11-28
Lapauw, T., Lambrinou, K., Cabioch, T., Halim, J., Lu, J., Pesach, A., . . . Vleugels, J. (2016). Synthesis of the new MAX phase Zr2AlC. Journal of the European Ceramic Society, 36(8), 1847-1853
Open this publication in new window or tab >>Synthesis of the new MAX phase Zr2AlC
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2016 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 36, no 8, p. 1847-1853Article in journal (Refereed) Published
Abstract [en]

This study reports on the first experimental evidence of the existence of the Zr2AlC MAX phase, synthesised by means of reactive hot pressing of a ZrH2, Al and C powder mixture. The crystal structure of this compound was investigated by X-ray and neutron diffraction. The lattice parameters were determined and confirmed by high-resolution transmission electron microscopy. The effect of varying the synthesis temperature was investigated, indicating a relatively narrow temperature window for the synthesis of Zr2AlC. ZrC was always present as a secondary phase by hot pressing in the 1475-1575 degrees C range.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2016
Keywords
MAX phase ceramics; Diffraction analysis; Reactive hot pressing
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-127738 (URN)10.1016/j.jeurceramsoc.2016.02.044 (DOI)000374082900001 ()
Note

Funding Agencies|Agency for Innovation by Science and Technology (IWT), Flanders, Belgium [131081]; European Atomic Energy Communitys (Euratom) Seventh Framework Programme FP7 [604862]; EERA (European Energy Research Alliance) Joint Programme on Nuclear Materials (JPNM); Hercules Foundation [ZW09-09]; Swedish Foundation for Strategic Research through the Synergy Grant FUNCASE; Swedish Foundation for Strategic Research through the Future Research Leaders 5 program

Available from: 2016-05-12 Created: 2016-05-12 Last updated: 2018-03-21
Lapauw, T., Halim, J., Lu, J., Cabioch, T., Hultman, L., Barsoum, M., . . . Vleugels, J. (2016). Synthesis of the novel Zr3AlC2 MAX phase. Journal of the European Ceramic Society, 36(3), 943-947
Open this publication in new window or tab >>Synthesis of the novel Zr3AlC2 MAX phase
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2016 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 36, no 3, p. 943-947Article in journal (Refereed) Published
Abstract [en]

Herein we report, for the first time, on the synthesis and structural characterization of the Zr-based MAX phase, Zr3AlC2, fabricated by reactive hot pressing of ZrH2, Al, and C powders. The crystal structure of Zr3AlC2 was determined by X-ray diffraction and high resolution transmission electron microscopy to be the hexagonal space group P63/mmc. The a and c lattice parameters are 3.33308(6)angstrom and 19.9507(3)angstrom, respectively. The samples include the secondary phases ZrC and Zr-Al intermetallics as confirmed by quantitative electron probe microanalysis. The Vickers hardness, using a force of 30 N, was measured to be 4.4 +/- 0.4 GPa. (C) 2015 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2016
Keywords
MAX phase; X-ray diffraction; Reactive hot pressing; Hydrides
National Category
Inorganic Chemistry Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-124461 (URN)10.1016/j.jeurceramsoc.2015.10.011 (DOI)000367407900066 ()
Note

Funding Agencies|Agency for Innovation by Science and Technology (IWT), Flanders, Belgium [131081]; European Atomic Energy Communitys (Euratom) Seventh Framework Programme [604862]; Hercules Foundation [ZW09-09]; Swedish Government; Swedish Government Strategic Research Area Grant in Materials Science (MAT-LiU)

Available from: 2016-02-02 Created: 2016-02-01 Last updated: 2017-11-30
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