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Lu, Jun
Publications (10 of 123) Show all publications
Magnuson, M., Tengdelius, L., Greczynski, G., Eriksson, F., Jensen, J., Lu, J., . . . Högberg, H. (2019). Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 37(2), Article ID 021506.
Open this publication in new window or tab >>Compositional dependence of epitaxial Tin+1SiCn MAX-phase thin films grown from a Ti3SiC2 compound target
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2019 (English)In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 2, article id 021506Article in journal (Refereed) Published
Abstract [en]

The authors investigate sputtering of a Ti3SiC2 compound target at temperatures ranging from RT (no applied external heating) to 970 °C as well as the influence of the sputtering power at 850 °C for the deposition of Ti3SiC2 films on Al2O3(0001) substrates. Elemental composition obtained from time-of-flight energy elastic recoil detection analysis shows an excess of carbon in all films, which is explained by differences in the angular distribution between C, Si, and Ti, where C scatters the least during sputtering. The oxygen content is 2.6 at. % in the film deposited at RT and decreases with increasing deposition temperature, showing that higher temperatures favor high purity films. Chemical bonding analysis by x-ray photoelectron spectroscopy shows C–Ti and Si–C bonding in the Ti3SiC2 films and Si–Si bonding in the Ti3SiC2 compound target. X-ray diffraction reveals that the phases Ti3SiC2, Ti4SiC3, and Ti7Si2C5 can be deposited from a Ti3SiC2 compound target at substrate temperatures above 850 °C and with the growth of TiC and the Nowotny phase Ti5Si3Cx at lower temperatures. High-resolution scanning transmission electron microscopy shows epitaxial growth of Ti3SiC2, Ti4SiC3, and Ti7Si2C5 on TiC at 970 °C. Four-point probe resistivity measurements give values in the range ∼120 to ∼450 μΩ cm and with the lowest values obtained for films containing Ti3SiC2, Ti4SiC3, and Ti7Si2C5.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-154004 (URN)10.1116/1.5065468 (DOI)000460437200051 ()
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 Energy Research [43606-1]; Carl Tryggers Foundation [CTS16:303, CTS14:310, CTS 17:166]; Knut 

Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-03-20Bibliographically approved
Landälv, L., Carlström, C.-F., Lu, J., Primetzhofer, D., Jöesaar, M. J., Ahlgren, M., . . . Eklund, P. (2019). Phase composition and transformations in magnetron-sputtered (Al,V)2O3 coatings. Thin Solid Films
Open this publication in new window or tab >>Phase composition and transformations in magnetron-sputtered (Al,V)2O3 coatings
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2019 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731Article in journal (Refereed) In press
Abstract [en]

Coatings of (Al1-xVx)2O3, with x ranging from 0 to 1, were deposited by pulsed DC reactive sputter deposition on Si(100) at a temperature of 550 °C. XRD showed three different crystal structures depending on V-metal fraction in the coating: α-V2O3 rhombohedral structure for 100 at.% V, a defect spinel structure for the intermediate region, 63–42 at.% V. At lower V-content, 18 and 7 at.%, a gamma-alumina-like solid solution was observed, shifted to larger d-spacing compared to pure γ-Al2O3. The microstructure changes from large columnar faceted grains for α-V2O3 to smaller equiaxed grains when lowering the vanadium content towards pure γ-Al2O3. Annealing in air resulted in formation of V2O5 crystals on the surface of the coating after annealing to 500 °C for 42 at.% V and 700 °C for 18 at.% V metal fraction respectively. The highest thermal stability was shown for pure γ-Al2O3-coating, which transformed to α-Al2O3 after annealing to 1100 °C. Highest hardness was observed for the Al-rich oxides, ~24 GPa. The latter decreased with increasing V-content, larger than 7 at.% V metal fraction. The measured hardness after annealing in air decreased in conjunction with the onset of further oxidation of the coatings.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Aluminum vanadium oxide Pulsed DC magnetron sputtering Annealing V2O5 AlVO4 AlVO3
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-159749 (URN)10.1016/j.tsf.2019.06.019 (DOI)
Available from: 2019-08-20 Created: 2019-08-20 Last updated: 2019-08-20Bibliographically approved
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
Paul, B., Björk, E. M., Kumar, A., Lu, J. & Eklund, P. (2018). Nanoporous Ca3Co4O9 Thin Films for Transferable Thermoelectrics. ACS applied energy materials, 1(5), 2261-2268
Open this publication in new window or tab >>Nanoporous Ca3Co4O9 Thin Films for Transferable Thermoelectrics
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2018 (English)In: ACS applied energy materials, ISSN 2574-0962, Vol. 1, no 5, p. 2261-2268Article in journal (Refereed) Published
Abstract [en]

The development of high-performance and transferable thin-film thermoelectric materials is important for low-power applications, e.g., to power wearable electronics, and for on-chip cooling. Nanoporous films offer an opportunity to improve thermoelectric performance by selectively scattering phonons without affecting electronic transport. Here, we report the growth of nanoporous Ca3Co4O9 thin films by a sequential sputtering-annealing method. Ca3Co4O9 is promising for its high Seebeck coefficient and good electrical conductivity and important for its nontoxicity, low cost, and abundance of its constituent raw materials. To grow nanoporous films, multilayered CaO/CoO films were deposited on sapphire and mica substrates by rf-magnetron reactive sputtering from elemental Ca and Co targets, followed by annealing at 700 C to form the final phase of Ca3Co4O9. This phase transformation is accompanied by a volume contraction causing formation of nanopores in the film. The thermoelectric propoperties of the nanoporous Ca3Co4O9 films can be altered by controlling the porosity. The lowest electrical resistivity is ~7 mO cm, yielding a power factor of 2.32 × 10-4 Wm-1K-2 near room temperature. Furthermore, the films are transferable from the primary mica substrates to other arbitrary polymer platforms by simple dry transfer, which opens an opportunity of low-temperature use these materials.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
Ca3Co4O9; nanoporous; thermoelectrics; thin film; transferable
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-155845 (URN)10.1021/acsaem.8b00333 (DOI)000458705500058 ()29905306 (PubMedID)
Available from: 2019-03-29 Created: 2019-03-29 Last updated: 2019-04-04Bibliographically 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: 2019-06-28Bibliographically 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
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