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Author |
van der Torren, A.J.H.; Liao, Z.; Xu, C.; Gauquelin, N.; Yin, C.; Aarts, J.; van der Molen, S.J. |
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Title |
Formation of a conducting LaAlO3/SrTiO3 interface studied by low-energy electron reflection during growth |
Type |
A1 Journal Article |
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Year |
2017 |
Publication |
Physical Review Materials |
Abbreviated Journal |
Phys. Rev. Materials |
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Volume |
1 |
Issue |
7 |
Pages |
075001 |
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Keywords |
A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ; |
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Abstract |
The two-dimensional electron gas occurring between the band insulators SrTiO 3 and LaAlO 3 continues to attract considerable interest, due to the possibility of dynamic control over the carrier density, and the ensuing phenomena such as magnetism and superconductivity. The formation of this conducting interface is sensitive to the growth conditions, but despite numerous investigations, there are still questions about the details of the physics involved. In particular, not much is known about the electronic structure of the growing LaAlO 3 layer at the growth temperature (around 800 ◦ C) in oxygen (pressure around 5 × 10 −5 mbar), since analysis techniques at these conditions are not readily available. We developed a pulsed laser deposition system inside a low-energy electron microscope in order to study this issue. The setup allows for layer-by-layer growth control and in-situ measurements of the angle-dependent electron reflection intensity, which can be used as a fingerprint of the electronic structure of the surface layers during growth. By using different substrate terminations and growth conditions we observe two families of reflectivity maps, which we can connect either to samples with an AlO 2 -rich surface and a conducting interface; or to samples with a LaO-rich surface and an insulating interface. Our observations emphasize that substrate termination and stoichiometry determine the electronic structure of the growing layer, and thereby the conductance of the interface. |
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Wos |
000418770200003 |
Publication Date |
2017-12-06 |
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ISSN |
2475-9953 |
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Times cited |
2 |
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Not_Open_Access |
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Notes |
Nederlandse Organisatie voor Wetenschappelijk Onderzoek; Fonds Wetenschappelijk Onderzoek, G.0044.13N ; European Cooperation in Science and Technology, MP 1308 ; We want to acknowledge Ruud Tromp, Daniel Gee- len, Johannes Jobst, Regina Dittmann, Gert Jan Koster, Guus Rijnders and Jo Verbeek for discussions and ad- vice and Ruud van Egmond and Marcel Hesselberth for technical assistance. This work was supported by the Netherlands Organization for Scientific Research (NWO) by means of an ”NWO Groot” grant and by the Leiden- Delft Consortium NanoFront. The work is part of the re- search programmes NWOnano and DESCO, which are fi- nanced by NWO. N.G. acknowledges funding through the GOA project “Solarpaint” of the University of Antwerp and from the FWO project G.0044.13N (Charge order- ing). The microscope used in this work was partly funded by the Hercules Fund from the Flemish Government. We would also like to acknowledge networking support by the COST Action MP 1308 (COST TO-BE). |
Approved |
Most recent IF: NA |
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Call Number |
EMAT @ emat @ |
Serial |
4903 |
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Author |
Yin, C.; Krishnan, D.; Gauquelin, N.; Verbeeck, J.; Aarts, J. |
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Title |
Controlling the interfacial conductance in LaAlO3/SrTiO3 in 90 degrees off-axis sputter deposition |
Type |
A1 Journal article |
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Year |
2019 |
Publication |
Physical review materials |
Abbreviated Journal |
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Volume |
3 |
Issue |
3 |
Pages |
034002 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
We report on the fabrication of conducting interfaces between LaAlO3 and SrTiO3 by 90 degrees off-axis sputtering in an Ar atmosphere. At a growth pressure of 0.04 mbar the interface is metallic, with a carrier density of the order of 1 x 10(13) cm(-2) at 3 K. By increasing the growth pressure, we observe an increase of the out-of-plane lattice constants of the LaAlO3 films while the in-plane lattice constants do not change. Also, the low-temperature sheet resistance increases with increasing growth pressure, leading to an insulating interface when the growth pressure reaches 0.10 mbar. We attribute the structural variations to an increase of the La/Al ratio, which also explains the transition from metallic behavior to insulating behavior of the interfaces. Our research shows that the control which is furnished by the Ar pressure makes sputtering as versatile a process as pulsed laser deposition, and emphasizes the key role of the cation stoichiometry of LaAlO3 in the formation of the conducting interface. |
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Wos |
000461077100002 |
Publication Date |
2019-03-12 |
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ISSN |
2475-9953 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.926 |
Times cited |
4 |
Open Access |
Not_Open_Access |
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Notes |
; We thank Nikita Lebedev, Aymen Ben Hamida, and Prateek Kumar for useful discussions and Giordano Mattoni, Jun Wang, Vincent Joly, and Hozanna Miro for their technical assistance. We also thank Jean-Marc Triscone and his group for sharing their design of the sputtering system with us. This work is part of the FOM research programme DESCO with Project No. 149, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO). C.Y. is supported by China Scholarship Council (CSC) with Grant No. 201508110214. N.G., D.K., and J.V. acknowledge financial support from the GOA project “Solarpaint” of the University of Antwerp. ; |
Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:158547 |
Serial |
5243 |
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Author |
Yasui, Y.; Lahabi, K.; Fernández Becerra, V.; Fermin, R.; Anwar, M.S.; Yonezawa, S.; Terashima, T.; Milošević, M.V.; Aarts, J.; Maeno, Y. |
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Title |
Spontaneous emergence of Josephson junctions in homogeneous rings of single-crystal Sr₂RuO₄ |
Type |
A1 Journal article |
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Year |
2020 |
Publication |
npj Quantum Materials |
Abbreviated Journal |
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Volume |
5 |
Issue |
1 |
Pages |
21-28 |
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Keywords |
A1 Journal article; Condensed Matter Theory (CMT) |
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Abstract |
The chiral p-wave order parameter in Sr2RuO4 would make it a special case amongst the unconventional superconductors. A consequence of this symmetry is the possible existence of superconducting domains of opposite chirality. At the boundary of such domains, the locally suppressed condensate can produce an intrinsic Josephson junction. Here, we provide evidence of such junctions using mesoscopic rings, structured from Sr2RuO4 single crystals. Our order parameter simulations predict such rings to host stable domain walls across their arms. This is verified with transport experiments on loops, with a sharp transition at 1.5 K, which show distinct critical current oscillations with periodicity corresponding to the flux quantum. In contrast, loops with broadened transitions at around 3 K are void of such junctions and show standard Little-Parks oscillations. Our analysis demonstrates the junctions are of intrinsic origin and makes a compelling case for the existence of superconducting domains. |
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000525721000001 |
Publication Date |
2020-04-09 |
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ISSN |
2397-4648 |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
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Times cited |
10 |
Open Access |
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Notes |
; The authors would like to thank S. Goswami, A. Singh, M. Kupryianov, S. Bakurskiy, J. Jobst, T. Nakamura, K. Adachi, Y. Liu, and Y. Asano for valuable discussions and comments, and F. Hubler, Y. Nakamura, and Y. Yamaoka for their technical contribution. This work was supported by a Grant-in-Aid for Scientific Research on Innovative Areas “Topological Materials Science” (KAKENHI Grant Nos. JP15H05852, JP15K21717, JP15H05851), JSPS-EPSRC Core-to-Core program (A. Advanced Research Network), JSPS research fellow (KAKENHI Grant No. JP16J10404), Grant-in-Aid JSPS KAKENHI JP26287078 and JP17H04848, and the Netherlands Organisation for Scientific Research (NWO/OCW), as part of the Frontiers of Nanoscience program. V.F.B. acknowledges support from the Foundation for Polish Science through the IRA Programme co-financed by EU within SG OP. ; |
Approved |
Most recent IF: NA |
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Call Number |
UA @ admin @ c:irua:168553 |
Serial |
6613 |
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Author |
Lebedev, N.; Stehno, M.; Rana, A.; Reith, P.; Gauquelin, N.; Verbeeck, J.; Hilgenkamp, H.; Brinkman, A.; Aarts, J. |
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Title |
Gate-tuned anomalous Hall effect driven by Rashba splitting in intermixed LaAlO3/GdTiO3/SrTiO3 |
Type |
A1 Journal article |
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Year |
2021 |
Publication |
Scientific Reports |
Abbreviated Journal |
Sci Rep-Uk |
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Volume |
11 |
Issue |
1 |
Pages |
10726 |
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Keywords |
A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT) |
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Abstract |
The Anomalous Hall Effect (AHE) is an important quantity in determining the properties and understanding the behaviour of the two-dimensional electron system forming at the interface of SrTiO<sub>3</sub>-based oxide heterostructures. The occurrence of AHE is often interpreted as a signature of ferromagnetism, but it is becoming more and more clear that also paramagnets may contribute to AHE. We studied the influence of magnetic ions by measuring intermixed LaAlO<sub>3</sub>/GdTiO<sub>3</sub>/SrTiO<sub>3</sub>at temperatures below 10 K. We find that, as function of gate voltage, the system undergoes a Lifshitz transition while at the same time an onset of AHE is observed. However, we do not observe clear signs of ferromagnetism. We argue the AHE to be due to the change in Rashba spin-orbit coupling at the Lifshitz transition and conclude that also paramagnetic moments which are easily polarizable at low temperatures and high magnetic fields lead to the presence of AHE, which needs to be taken into account when extracting carrier densities and mobilities. |
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Wos |
000658820100014 |
Publication Date |
2021-05-21 |
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ISSN |
2045-2322 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
4.259 |
Times cited |
5 |
Open Access |
OpenAccess |
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Notes |
J.V. and N.G. acknowledge funding from the Geconcentreerde Onderzoekacties (GOA) project “Solarpaint” of the University of Antwerp and the European Union’s horizon 2020 research and innovation programme ESTEEM3 under grant agreement 823717. The Qu-Ant-EM microscope used in this study was partly funded by the Hercules fund from the Flemish Government.; esteem3TA; esteem3reported |
Approved |
Most recent IF: 4.259 |
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Call Number |
EMAT @ emat @c:irua:179608 |
Serial |
6822 |
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Author |
Lebedev, N.; Huang, Y.; Rana, A.; Jannis, D.; Gauquelin, N.; Verbeeck, J.; Aarts, J. |
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Title |
Resistance minimum in LaAlO3/Eu1-xLaxTiO3/SrTiO3 heterostructures |
Type |
A1 Journal article |
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Year |
2022 |
Publication |
Physical review materials |
Abbreviated Journal |
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Volume |
6 |
Issue |
7 |
Pages |
075003-75010 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
In this paper we study LaAlO3/Eu1-xLaxTiO3/SrTiO3 structures with nominally x = 0, 0.1 and different thicknesses of the Eu1-xLaxTiO3 layer. We observe that both systems have many properties similar to previously studied LaAlO3/EuTiO3/SrTiO3 and other oxide interfaces, such as the formation of a two-dimensional electron liquid for two unit cells of Eu1-xLaxTiO3; a metal-insulator transition driven by the increase in thickness of the Eu1-xLaxTiO3 layer; the presence of an anomalous Hall effect when driving the systems above the Lifshitz point with a back-gate voltage; and a minimum in the temperature dependence of the sheet resistance below the Lifshitz point in the one-band regime, which becomes more pronounced with increasing negative gate voltage. However, and notwithstanding the likely presence of magnetism in the system, we do not attribute that minimum to the Kondo effect, but rather to the properties of the SrTiO3 crystal and the inevitable effects of charge trapping when using back gates. |
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Wos |
000834035300001 |
Publication Date |
2022-07-12 |
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ISSN |
2475-9953 |
ISBN |
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Additional Links |
UA library record; WoS full record |
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Impact Factor |
3.4 |
Times cited |
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Open Access |
OpenAccess |
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Notes |
N.L. and J.A. gratefully acknowledge the financial support of the research program DESCO, which is financed by the Netherlands Organisation for Scientific Research (NWO). J.V. and N.G. acknowledge funding from the Geconcentreerde Onderzoekacties (GOA) project “Solarpaint” of the University of Antwerp and the European Union’s horizon 2020 research and innovation programme under grant agreement №823717 – ESTEEM3. The QuAnt-EM microscope used in this study was partly funded by the Hercules fund from the Flemish Government. The authors want to thank M. Stehno, G. Koster, and F.J.G. Roesthuis for useful discussions.; esteem3reported; esteem3TA |
Approved |
Most recent IF: 3.4 |
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Call Number |
UA @ admin @ c:irua:189674 |
Serial |
7094 |
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Author |
Lebedev, N.; Stehno, M.; Rana, A.; Gauquelin, N.; Verbeeck, J.; Brinkman, A.; Aarts, J. |
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Title |
Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO₃/SrTiO₃ interfaces |
Type |
A1 Journal article |
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Year |
2020 |
Publication |
Journal Of Physics-Condensed Matter |
Abbreviated Journal |
J Phys-Condens Mat |
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Volume |
33 |
Issue |
5 |
Pages |
055001 |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
We have studied the transport properties of LaTiO3/SrTiO3 (LTO/STO) heterostructures. In spite of 2D growth observed in reflection high energy electron diffraction, transmission electron microscopy images revealed that the samples tend to amorphize. Still, we observe that the structures are conducting, and some of them exhibit high conductance and/or superconductivity. We established that conductivity arises mainly on the STO side of the interface, and shows all the signs of the two-dimensional electron gas usually observed at interfaces between STO and LTO or LaAlO3, including the presence of two electron bands and tunability with a gate voltage. Analysis of magnetoresistance (MR) and superconductivity indicates the presence of spatial fluctuations of the electronic properties in our samples. That can explain the observed quasilinear out-of-plane MR, as well as various features of the in-plane MR and the observed superconductivity. |
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Wos |
000588209300001 |
Publication Date |
2020-10-14 |
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Edition |
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ISSN |
0953-8984 |
ISBN |
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Additional Links |
UA library record; WoS full record; WoS citing articles |
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Impact Factor |
2.7 |
Times cited |
1 |
Open Access |
OpenAccess |
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Notes |
; NL and JA gratefully acknowledge the financial support of the research program DESCO, which is financed by the Netherlands Organisation for Scientific Research (NWO). The authors thank J Jobst, S Smink, K Lahabi and G Koster for useful discussion. ; |
Approved |
Most recent IF: 2.7; 2020 IF: 2.649 |
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Call Number |
UA @ admin @ c:irua:173679 |
Serial |
6545 |
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