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Liu, Ruisheng S.
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Publications (10 of 10) Show all publications
Pettersson, H., Liu, R. S., Suyatin, D. & Samuelson, L. (2008). Assembling ferromagnetic single-electron transistors by atomic force microscopy. In: Rahman, Faiz (Ed.), Nanostructures in electronics and photonics: (pp. 29-40). Singapore: Pan Stanford Publishing
Open this publication in new window or tab >>Assembling ferromagnetic single-electron transistors by atomic force microscopy
2008 (English)In: Nanostructures in electronics and photonics / [ed] Rahman, Faiz, Singapore: Pan Stanford Publishing, 2008, p. 29-40Chapter in book (Refereed)
Place, publisher, year, edition, pages
Singapore: Pan Stanford Publishing, 2008
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:hh:diva-22988 (URN)978-981-4241-10-6 (ISBN)978-981-4241-12-0 (ISBN)
Available from: 2013-06-19 Created: 2013-06-19 Last updated: 2018-04-03Bibliographically approved
Pettersson, H., Liu, R. S., Suyatin, D. & Samuelson, L. (2008). Assembling ferromagnetic single-electron transistors with atomic force microscopy. In: Faiz Rahman (Ed.), Nanostructures in Electronics and Photonics: (pp. 29-40). London: Pan Stanford Publishing
Open this publication in new window or tab >>Assembling ferromagnetic single-electron transistors with atomic force microscopy
2008 (English)In: Nanostructures in Electronics and Photonics / [ed] Faiz Rahman, London: Pan Stanford Publishing, 2008, p. 29-40Chapter in book (Other academic)
Abstract [en]

Ferromagnetic Single Electron Transistors (F-SETs) comprise ferromagnetic electrodes connected to a ferromagnetic- or non-magnetic central island via tunnel barriers. These devices are important for studies of spin-transport physics in confined structures. Here we describe the development of a novel type of AFMassembled nano-scale F-SETs suitable for spin-transport investigations at temperatures above 4.2 K. The ingenious fabrication technique means that their electrical characteristics can be tuned in real-time during the fabrication sequence by re-positioning the central island with Ångström precision. © 2008 by Pan Stanford Publishing Pte. Ltd. All rights reserved.

Place, publisher, year, edition, pages
London: Pan Stanford Publishing, 2008
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:hh:diva-37577 (URN)2-s2.0-84880187788 (Scopus ID)9789814241106 (ISBN)
Available from: 2018-07-16 Created: 2018-07-16 Last updated: 2018-07-16Bibliographically approved
Liu, R. S., Canali, C. M., Samuelson, L. & Pettersson, H. (2008). Magnetoresistance studies on CoAl OX Au and CoAl OX NiAu tunnel structures. Applied Physics Letters, 93(20), 203107-203107-3
Open this publication in new window or tab >>Magnetoresistance studies on CoAl OX Au and CoAl OX NiAu tunnel structures
2008 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 20, p. 203107-203107-3Article in journal (Refereed) Published
Abstract [en]

We report on magnetoresistance (MR) studies on CoAl OX Au and CoAl OX NiAu magnetic tunnel junctions. In spite of the fact that the difference between the two samples is merely a 3 nm thick Ni layer, there is a sharp contrast in MR behavior indicating that the electronic structure at the interface between the ferromagnetic electrodes and the insulating barrier dominates the MR signal. The former sample exhibits a clear tunneling anisotropic MR (TAMR), with the characteristic correlation between resistance and current direction, in contrast to the latter sample which displays a conventional tunneling MR (TMR) dominated by the relative orientation between the magnetization directions of the two electrodes. In addition, the TAMR has a much stronger temperature dependence than the TMR, indicating a much faster drop-off of the tunneling density of states anisotropy than the tunneling electron spin polarization with increasing temperature. Finally, we propose a possible simple way to distinguish TAMR from normal TMR by measuring the resistance of the device at different angles of the external magnetic field. 2008 American Institute of Physics.

Place, publisher, year, edition, pages
New York: American Institute of Physics (AIP), 2008
Keywords
Tunnel junctions, Anisotropy, Coal, Coal industry, Electric resistance, Electrodes, Electronic structure, Magnetic field effects, Magnetic fields, Magnetoelectronics, Magnetoresistance, Semiconductor junctions, Spin dynamics, Tunneling (excavation), Tunnels
National Category
Physical Sciences
Identifiers
urn:nbn:se:hh:diva-3464 (URN)10.1063/1.3000614 (DOI)000261141400050 ()2-s2.0-56849094689 (Scopus ID)
Available from: 2010-02-11 Created: 2009-12-01 Last updated: 2018-04-03Bibliographically approved
Liu, R., Michalak, L., Canali, C., Samuelson, L. & Pettersson, H. (2008). Tunneling Anisotropic Magnetoresistance in Co/AlOx /Au Tunnel Junctions. In: : . Paper presented at 2008 APS March Meeting, Monday–Friday, March 10–14, 2008, New Orleans, Louisiana, US.
Open this publication in new window or tab >>Tunneling Anisotropic Magnetoresistance in Co/AlOx /Au Tunnel Junctions
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2008 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

We observe spin-valve-like effects in nano-scaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:hh:diva-22399 (URN)
Conference
2008 APS March Meeting, Monday–Friday, March 10–14, 2008, New Orleans, Louisiana, US
Note

Poster number: S32.00008

The authors acknowledge financial support from Halmstad University, Kalmar University, the Swedish Research Council, the Swedish National Board for Industrial and Technological Development, the Office of Naval Research, KAWF and SSF.

Available from: 2013-06-04 Created: 2013-06-04 Last updated: 2018-04-03Bibliographically approved
Liu, R., Michalak, L., Canali, C. M., Samuelson, L. & Pettersson, H. (2008). Tunneling anisotropic magnetoresistance in Co/AlOx/Au tunnel junctions. Nano letters (Print), 8(3), 848-852
Open this publication in new window or tab >>Tunneling anisotropic magnetoresistance in Co/AlOx/Au tunnel junctions
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2008 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 3, p. 848-852Article in journal (Refereed) Published
Abstract [en]

We observe spin-valve-like effects in nanoscaled thermally evaporated Co/AlOx/Au tunnel junctions. The tunneling magnetoresistance is anisotropic and depends on the relative orientation of the magnetization direction of the Co electrode with respect to the current direction. We attribute this effect to a two-step magnetization reversal and an anisotropic density of states resulting from spin-orbit interaction. The results of this study points to future applications of novel spintronics devices involving only one ferromagnetic layer.

Place, publisher, year, edition, pages
Washington: American Chemical Society, 2008
Keywords
Current directions, Density of state, Ferromagnetic layers, Future applications, Magnetization - reversals, Magnetization directions, Nanoscaled, Relative orientations, Spin valves, Spin-orbit interactions, Spintronics devices, Tunneling anisotropic magnetoresistances, Tunneling magnetoresistances
National Category
Physical Sciences
Identifiers
urn:nbn:se:hh:diva-3465 (URN)10.1021/nl072985p (DOI)000253947400015 ()2-s2.0-56849092725 (Scopus ID)
Available from: 2010-02-11 Created: 2009-12-01 Last updated: 2018-04-03Bibliographically approved
Liu, R., Suyatin, D., Pettersson, H. & Samuelson, L. (2007). Assembling ferromagnetic single-electron transistors by atomic force microscopy. Nanotechnology, 18(5), 055302
Open this publication in new window or tab >>Assembling ferromagnetic single-electron transistors by atomic force microscopy
2007 (English)In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 18, no 5, p. 055302-Article in journal (Refereed) Published
Abstract [en]

We demonstrate the assembly of nanoscale ferromagnetic single-electron transistors using atomic force microscopy for imaging as well as for nanoscale manipulation. A single 30 nm Au disc, forming the central island of the transistor, is manipulated with angstrom precision into the gap between a plasma-oxidized Ni source and drain electrodes. The tunnel resistances can be tuned in real time during the device fabrication by repositioning the Au disc. Transport measurements reveal long-term stable single-electron transistor characteristics at 4.2 K. The well-controlled devices with very small central islands facilitate future in-depth studies of the interplay between Coulomb blockade, spin-dependent tunnelling and spin accumulation in ferromagnetic single-electron transistors at elevated temperatures.

Place, publisher, year, edition, pages
Bristol: Institute of Physics (IOP), 2007
Keywords
Atomic force microscopy, Coulomb blockade, Electrodes, Electron tunneling, Ferromagnetic materials, Imaging techniques, Plasmas, Drain electrodes, Plasma-oxidized, Single-electron transistors, Spin-dependent tunnelling, Transistors, Atomic force microscopy, Electrode, Semiconductor, Single electron transistor
National Category
Physical Sciences
Identifiers
urn:nbn:se:hh:diva-3467 (URN)10.1088/0957-4484/18/5/055302 (DOI)000243854900005 ()2-s2.0-33947491239 (Scopus ID)
Available from: 2010-02-10 Created: 2009-12-01 Last updated: 2018-04-03Bibliographically approved
Liu, R., Pettersson, H., Michalak, L., Canali, C. M., Suyatin, D. & Samuelson, L. (2007). Large magnetoresistance in Co/Ni/Co ferromagnetic single electron transistors. Applied Physics Letters, 90(12), 123111
Open this publication in new window or tab >>Large magnetoresistance in Co/Ni/Co ferromagnetic single electron transistors
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2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 12, p. 123111-Article in journal (Refereed) Published
Abstract [en]

The authors report on magnetotransport investigations of nanoscaled ferromagnetic Co/Ni/Co single electron transistors. As a result of reduced size, the devices exhibit single electron transistor characteristics at 4.2 K. Magnetotransport measurements carried out at 1.8 K reveal tunneling magnetoresistance (TMR) traces with negative coercive fields, which the authors interpret in terms of a switching mechanism driven by the shape anisotropy of the central wirelike Ni island. A large TMR of about 18% is observed within a finite source-drain bias regime. The TMR decreases rapidly with increasing bias, which the authors tentatively attribute to excitation of magnons in the central island.

Place, publisher, year, edition, pages
New York: American Institute of Physics, 2007
Keywords
Cobalt, Nickel, Ferromagnetic materials, Single electron transistors, Tunnelling magnetoresistance, Magnetoresistive devices, Coercive force, Magnetic anisotropy, Magnons
National Category
Physical Sciences
Identifiers
urn:nbn:se:hh:diva-3466 (URN)10.1063/1.2714289 (DOI)000245135800095 ()2-s2.0-33947600114 (Scopus ID)
Available from: 2010-02-11 Created: 2009-12-01 Last updated: 2018-04-03Bibliographically approved
Liu, R., Pettersson, H., Suyatin, D., Michalak, L., Canali, C. M. & Samuelson, L. (2007). Nanoscaled Ferromagnetic Single-Electron Transistors. In: 2007 7th IEEE International Conference on Nanotechnology - IEEE-NANO 2007, Proceedings. Paper presented at 7th IEEE Conference on Nanotechnology Location, Hong Kong, PEOPLES R CHINA, AUG 02-05, 2007 (pp. 420-421). Piscataway, N.J.: IEEE Press
Open this publication in new window or tab >>Nanoscaled Ferromagnetic Single-Electron Transistors
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2007 (English)In: 2007 7th IEEE International Conference on Nanotechnology - IEEE-NANO 2007, Proceedings, Piscataway, N.J.: IEEE Press, 2007, p. 420-421Conference paper, Published paper (Other academic)
Abstract [en]

We report on a summary of fabricating and characterizing nanoscaled ferromagnetic single-electron transistors (F-SETs). One type of device is assembled with an atomic force microscope. A single 30 nm Au disc, forming the central island of the transistor, is manipulated with Angstrom precision into the gap between plasma oxidized Ni source and drain electrodes which are designed with different geometries to facilitate magnetic moment reversal at different magnetic fields. The tunnel resistances can be tuned in real-time during the device fabrication by re-positioning the An disc. A second type of device with Co electrodes and a central Au island is fabricated using a high-precision alignment procedure invoked during e-beam writing. Both devices exhibit single-electron transistor characteristics at 4.2K. From magnetotransport measurements carried out at 1.7K, we found that it is more efficient to realize spin injection and detection in Co/Au/Co devices fabricated with the second technique. A maximum TMR of about 4% was observed in these devices.

Place, publisher, year, edition, pages
Piscataway, N.J.: IEEE Press, 2007
Keywords
Spintronics, Ferromagnetic Single-Electron Transistor, Coulomb Blockad, Tunneling Magnetoresistance
National Category
Engineering and Technology
Identifiers
urn:nbn:se:hh:diva-18860 (URN)10.1109/NANO.2007.4601223 (DOI)000261434900096 ()2-s2.0-52949147451 (Scopus ID)978-1-4244-0607-4 (ISBN)
Conference
7th IEEE Conference on Nanotechnology Location, Hong Kong, PEOPLES R CHINA, AUG 02-05, 2007
Note

©2007 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

Available from: 2012-06-27 Created: 2012-06-25 Last updated: 2018-04-03Bibliographically approved
Liu, R., Pettersson, H., Michalak, L., Canali, C. & Samuelson, L. (2007). Probing spin accumulation in Ni/Au/Ni single-electron transistors with efficient spin injection and detection electrodes. Nano letters (Print), 7(1), 81-85
Open this publication in new window or tab >>Probing spin accumulation in Ni/Au/Ni single-electron transistors with efficient spin injection and detection electrodes
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2007 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 7, no 1, p. 81-85Article in journal (Refereed) Published
Abstract [en]

We have investigated spin accumulation in Ni/Au/Ni single-electron transistors assembled by atomic force microscopy. The fabrication technique is unique in that unconventional hybrid devices can be realized with unprecedented control, including real-time tunable tunnel resistances. A grid of Au disks, 30 nm in diameter and 30 nm thick, is prepared on a SiO2 surface by conventional e-beam writing. Subsequently, 30 nm thick ferromagnetic Ni source, drain, and side-gate electrodes are formed in similar process steps. The width and length of the source and drain electrodes were different to exhibit different coercive switching fields. Tunnel barriers of NiO are realized by sequential Ar and O2 plasma treatment. By use of an atomic force microscope with specially designed software, a single nonmagnetic Au nanodisk is positioned into the 25 nm gap between the source and drain electrodes. The resistance of the device is monitored in real time while the Au disk is manipulated step-by-step with angstrom-level precision. Transport measurements in magnetic field at 1.7 K reveal no clear spin accumulation in the device, which can be attributed to fast spin relaxation in the Au disk. From numerical simulations using the rate-equation approach of orthodox Coulomb blockade theory, we can put an upper bound of a few nanoseconds on the spin-relaxation time for electrons in the Au disk. To confirm the magnetic switching characteristics and spin injection efficiency of the Ni electrodes, we fabricated a test structure consisting of a Ni/NiO/Ni magnetic tunnel junction with asymmetric dimensions of the electrodes similar to those of the single-electron transistors. Magnetoresistance measurements on the test device exhibited clear signs of magnetic reversal and a maximum tunneling magnetoresistance of 10%, from which we deduced a spin polarization of about 22% in the Ni electrodes. © 2007 American Chemical Society.

Place, publisher, year, edition, pages
Washington, DC: American Chemical Society (ACS), 2007
Keywords
Drain electrodes, Tunneling magnetoresistance, Magnetic switching, Single-electron transistors
National Category
Physical Sciences
Identifiers
urn:nbn:se:hh:diva-1380 (URN)10.1021/nl062146n (DOI)000243381300015 ()17212444 (PubMedID)2-s2.0-33846859553 (Scopus ID)2082/1759 (Local ID)2082/1759 (Archive number)2082/1759 (OAI)
Available from: 2008-05-06 Created: 2008-05-06 Last updated: 2018-04-03Bibliographically approved
Liu, R., Pettersson, H., Michalak, L., Canali, C. M. & Samuelson, L. (2006). Ferromagnetic single-electron transistors fabricated by atomic force microscopy. In: : . Paper presented at APS, March Meeting, 2006, Baltimore, USA.
Open this publication in new window or tab >>Ferromagnetic single-electron transistors fabricated by atomic force microscopy
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2006 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

We report on the fabrication and magneto-transport measurements of Ni/Au/Ni ferromagnetic single-electron transistors (F-SETs), fabricated by atomic force microscopy. By positioning a single Au disc (30 nm in diameter) into the gap between the Ni drain and source electrodes (of width 220 nm and 80 nm, respectively) step-by-step with Angstrom precision, and using plasma-processed NiOx as tunneling barriers, we can successfully fabricate F-SETs of high quality and substantial stability. The characteristic time interval of the device between two successive tunneling events is 10ps. The absence of any clear features in the transport related to the applied external magnetic field indicates that no spin-accumulation is maintained in the central Au disc. This interesting result indicates that the spin-relaxation time inside the central island should be shorter than 10ps. Based on these findings, we will discuss possible mechanisms of spin-relaxation in metal nano-structures triggered by spin-orbit interaction.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:hh:diva-22362 (URN)
Conference
APS, March Meeting, 2006, Baltimore, USA
Available from: 2013-05-28 Created: 2013-05-28 Last updated: 2018-04-03Bibliographically approved
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