Dr Steven Clowes
Lecturer, Postgraduate Tutor for ATI
Qualifications: MSc, PhD
Email: s.clowes@surrey.ac.uk
Phone: Work: 01483 68 9827
Room no: 12 ATI 02
Further information
Biography
1994 BSc in Physics from University of York, UK
1995 MSc in Surface Science from Loughborough University, UK
1999 PhD in Experimental Studies of Surface-Adsorbate Interactions and Surface magnetism from University of York, UK
1999-2001 Postdoctoral Research Associate at Rutgers University NJ, USA
2001-2007 Postdoctoral Research Associate at Imperial College London, UK
2007 Laboratory Manager of fabrication facilities for the ATI, University of Surrey
2007 EPSRC Advanced Research Fellow, ATI, University of Surrey
2012 Lecturer of Physics, Department of Physics, University of Surrey
Research Interests
- Study of spin dependent electron transport in semiconductor devices using optically orientated photo-conductivity measurements.
- Direct magnetic measurement of optically induced magnetism is doped nanocrystals.
- Optical control of spin transport in two dimensional topological insulators.
- Ultrafast spin dynamics in high spin-orbit coupled two dimensional systems.
- Quantum control of dopants in silicon for quantum information processing.
Current PhD projects available:
Measurement of spin polarised photocurrents in topological insulators
Surface gated InSb structures for spintronic applications
Research Collaborations
- Imperial College London
- National Physics Laboratory, UK
- Regensburg University, Germany
- University College London
Publications
Highlights
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(2013) 'Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars.'. Nature Publishing Group Nat Commun, England: 4doi: 10.1038/ncomms2466Full text is available at: http://epubs.surrey.ac.uk/755949/
Abstract
Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10(5) T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H(2) analogues, and for investigation of He(2), a bound molecule predicted under extreme field conditions.
- .
(2012) 'Observation of spin dependent photocoductivity in InSb quantum well nanowires'. AIP Applied Physics Letters, 101 (15)doi: 10.1063/1.4760223Full text is available at: http://epubs.surrey.ac.uk/735787/
Abstract
We report on the electrical detection of spin dependent photoconductivity in 500 nm wide InSb quantum well nanowires using the optical orientation of electron spins. By applying weak magnetic fields (≈ 200 mT), we observe a spin filtering effect of classical origin caused by spin dependent back scattering of electrons from the sidewalls. Spin dependent features in the longitudinal photovoltage decay with temperature and disappears at characteristic energy (≈ 50 K) consistent with the theoretical spin splitting and the thermal level broadening. We show that the observed signal is due to the inversion asymmetry of the quantum well, with an additional Zeeman contribution. © 2012 American Institute of Physics.
- . (2012) 'Temperature dependent optical properties of PbS nanocrystals.'. Nanotechnology, England: 23 (27)
- .
(2012) 'Transverse focusing of spin-polarized photocurrents'. American Physical Society Physical Review B (Condensed Matter and Materials Physics), 85 Article number 045431 Full text is available at: http://epubs.surrey.ac.uk/148877/
Abstract
We measure transverse magnetically focused photocurrent signals in an InSb/InAlSb quantum well device. Using optical spin orientation by modulated circularly polarized light an electron spin-dependent signal is observed due to the spin-orbit interaction. Simulations of the focusing signal are performed using a classical billiard ball model, which includes both spin precession and a spin-dependent electron energy. The simulated data suggest that a signal dependent on the helicity of the incident light is expected for a Rashba parameter α > 0.1 eVÅ and that a splitting of the focusing signal is not expected to be observed in linear polarized photocurrent and purely electrical measurements.
- .
(2012) 'Interplay of spin and orbital magnetogyrotropic photogalvanic effects in InSb/(Al,In) Sb quantum well structures'. PHYSICAL REVIEW B, 85 (4) Article number ARTN 045305 Full text is available at: http://epubs.surrey.ac.uk/56945/
- .
(2011) 'Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures'. IOP PUBLISHING LTD JOURNAL OF PHYSICS-CONDENSED MATTER, 23 (3) Article number ARTN 035801 Full text is available at: http://epubs.surrey.ac.uk/7763/
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(2010) 'Strong dependence of spin dynamics on the orientation of an external magnetic field for InSb and InAs'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 96 (11) Article number ARTN 111107 doi: 10.1063/1.3337111Full text is available at: http://epubs.surrey.ac.uk/7724/
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(2007) 'Electrical characterization of MgO tunnel barriers grown on InAs (001) epilayers'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 91 (12) Article number ARTN 122106 doi: 10.1063/1.2784933Full text is available at: http://epubs.surrey.ac.uk/470/
- . (2007) 'Oblique Hanle measurements of InAs/GaAs quantum dot spin-light emitting diodes'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 1289-1290.
- .
(2006) 'Oblique Hanle measurements of InAs/GaAs quantum dot spin-light emitting diodes'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 88 (2) Article number ARTN 022113 doi: 10.1063/1.2163074Full text is available at: http://epubs.surrey.ac.uk/350/
Journal articles
- .
(2013) 'Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars.'. Nature Publishing Group Nat Commun, England: 4doi: 10.1038/ncomms2466Full text is available at: http://epubs.surrey.ac.uk/755949/
Abstract
Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10(5) T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H(2) analogues, and for investigation of He(2), a bound molecule predicted under extreme field conditions.
- .
(2012) 'Observation of spin dependent photocoductivity in InSb quantum well nanowires'. AIP Applied Physics Letters, 101 (15)doi: 10.1063/1.4760223Full text is available at: http://epubs.surrey.ac.uk/735787/
Abstract
We report on the electrical detection of spin dependent photoconductivity in 500 nm wide InSb quantum well nanowires using the optical orientation of electron spins. By applying weak magnetic fields (≈ 200 mT), we observe a spin filtering effect of classical origin caused by spin dependent back scattering of electrons from the sidewalls. Spin dependent features in the longitudinal photovoltage decay with temperature and disappears at characteristic energy (≈ 50 K) consistent with the theoretical spin splitting and the thermal level broadening. We show that the observed signal is due to the inversion asymmetry of the quantum well, with an additional Zeeman contribution. © 2012 American Institute of Physics.
- . (2012) 'Temperature dependent optical properties of PbS nanocrystals.'. Nanotechnology, England: 23 (27)
- .
(2012) 'Transverse focusing of spin-polarized photocurrents'. American Physical Society Physical Review B (Condensed Matter and Materials Physics), 85 Article number 045431 Full text is available at: http://epubs.surrey.ac.uk/148877/
Abstract
We measure transverse magnetically focused photocurrent signals in an InSb/InAlSb quantum well device. Using optical spin orientation by modulated circularly polarized light an electron spin-dependent signal is observed due to the spin-orbit interaction. Simulations of the focusing signal are performed using a classical billiard ball model, which includes both spin precession and a spin-dependent electron energy. The simulated data suggest that a signal dependent on the helicity of the incident light is expected for a Rashba parameter α > 0.1 eVÅ and that a splitting of the focusing signal is not expected to be observed in linear polarized photocurrent and purely electrical measurements.
- .
(2012) 'Interplay of spin and orbital magnetogyrotropic photogalvanic effects in InSb/(Al,In) Sb quantum well structures'. PHYSICAL REVIEW B, 85 (4) Article number ARTN 045305 Full text is available at: http://epubs.surrey.ac.uk/56945/
- . (2011) 'Sophisticated test objects for the quality assurance of optical computed tomography scanners.'. Phys Med Biol, England: 56 (14), pp. 4177-4199.
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(2011) 'Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures'. IOP PUBLISHING LTD JOURNAL OF PHYSICS-CONDENSED MATTER, 23 (3) Article number ARTN 035801 Full text is available at: http://epubs.surrey.ac.uk/7763/
- .
(2010) 'Strong dependence of spin dynamics on the orientation of an external magnetic field for InSb and InAs'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 96 (11) Article number ARTN 111107 doi: 10.1063/1.3337111Full text is available at: http://epubs.surrey.ac.uk/7724/
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(2008) 'Interface properties of Pb/InAs planar structures for Andreev spectroscopy'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 92 (1) Article number ARTN 012501 doi: 10.1063/1.2828979Full text is available at: http://epubs.surrey.ac.uk/378/
- .
(2007) 'Electrical characterization of MgO tunnel barriers grown on InAs (001) epilayers'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 91 (12) Article number ARTN 122106 doi: 10.1063/1.2784933Full text is available at: http://epubs.surrey.ac.uk/470/
- . (2007) 'Low-temperature Schottky barrier tunneling in InSb/InxAl1-xSb quantum well heterostructures'. AMER PHYSICAL SOC PHYSICAL REVIEW B, 76 (8) Article number ARTN 085306
- . (2007) 'Preparation of InAs(001) surface for spin injection via a chemical route'. IOP PUBLISHING LTD JOURNAL OF PHYSICS D-APPLIED PHYSICS, 40 (10), pp. 3190-3193.
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(2007) 'Temperature insensitivity of the spin-polarization in Co2MnSi films on GaAs (001)'. IOP PUBLISHING LTD NEW JOURNAL OF PHYSICS, 9 Article number PII S1367-2630(07)34448-0 Full text is available at: http://epubs.surrey.ac.uk/124/
- . (2006) 'Exploration of the inherent magnetoresistance in InSb thin films'. IOP PUBLISHING LTD SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 21 (12), pp. 1543-1546.
- . (2006) 'Spin relaxation in n-InSb/AlInSb quantum wells'. IOP PUBLISHING LTD NEW JOURNAL OF PHYSICS, 8 Article number PII S1367-2630(06)15617-7
- . (2006) 'Spin relaxation by transient monopolar and bipolar optical orientation.'. Phys Rev Lett, United States: 96 (9)
- .
(2006) 'Oblique Hanle measurements of InAs/GaAs quantum dot spin-light emitting diodes'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 88 (2) Article number ARTN 022113 doi: 10.1063/1.2163074Full text is available at: http://epubs.surrey.ac.uk/350/
- .
(2006) 'Tuning the inherent magnetoresistance of InSb thin films'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 88 (1) Article number ARTN 012110 doi: 10.1063/1.2162666Full text is available at: http://epubs.surrey.ac.uk/454/
- . (2005) 'Evidence for dislocation-related amphoteric behaviour of Si dopant in high-mobility InSb thin films'. IOP PUBLISHING LTD SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 20 (12), pp. 1153-1156.
- . (2005) 'Temperature and doping dependence of spin relaxation in n-InAs'. AMERICAN PHYSICAL SOC PHYSICAL REVIEW B, 72 (8) Article number ARTN 085346
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(2005) 'Geometric manipulation of the high-field linear magnetoresistance in InSb epilayers on GaAs(001)'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 86 (20) Article number ARTN 202116 doi: 10.1063/1.1923755
- . (2005) 'Possibilities and limitations of point-contact spectroscopy for measurements of spin polarization'. AMERICAN PHYSICAL SOC PHYSICAL REVIEW B, 71 (10) Article number ARTN 104523
- . (2004) 'The role of impurity band conduction in the low temperature characteristics of thin InSb films grown by molecular beam epitaxy'. IOP PUBLISHING LTD SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 19 (12) Article number PII S0268-1242(04)81234-3 , pp. 1406-1410.
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(2004) 'Synthesis and physical properties of arc melted NiMnSb'. AMER INST PHYSICS JOURNAL OF APPLIED PHYSICS, 95 (12), pp. 8063-8068.doi: 10.1063/1.1739293
- . (2004) 'Spin polarization of the transport current at the free surface of bulk NiMnSb'. AMERICAN PHYSICAL SOC PHYSICAL REVIEW B, 69 (21) Article number ARTN 214425
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(2004) 'High-mobility thin InSb films grown by molecular beam epitaxy'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 84 (22), pp. 4463-4465.doi: 10.1063/1.1748850
- . (2004) 'Spin polarisation and anomalous Hall effect in NiMnSb films'. ELSEVIER SCIENCE BV JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, pp. E1399-E1401.
- . (2004) 'Thickness dependence of Hall transport in Ni1.15Mn0.85Sb thin films on silicon'. AMERICAN PHYSICAL SOC PHYSICAL REVIEW B, 69 (20) Article number ARTN 201305
- . (2004) 'Using PCAR to study Cu/Co bilayers'. ELSEVIER SCIENCE BV JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, pp. E1471-E1473.
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(2004) 'Large positive magnetoresistance in nonstoichiometric NiMnSb thin films on silicon'. AMER INST PHYSICS APPLIED PHYSICS LETTERS, 84 (13), pp. 2358-2360.doi: 10.1063/1.1691172
- . (2004) 'Analysis of steam oxidation of crystalline SIGE using AFM and CABOOM'. Proceedings - Electrochemical Society, 7, pp. 175-179.
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(2003) 'Effect of chemical substitution on the electronic properties of highly aligned thin films of Sr(2-x)A(x)FeMoO(6) (A=Ca, Ba, La; x=0, 0.1)'. AMER INST PHYSICS JOURNAL OF APPLIED PHYSICS, 94 (7), pp. 4714-4716.doi: 10.1063/1.1604477
- . (2002) 'Phosphine adsorption and the production of phosphide phases on Cu(001)'. ELSEVIER SCIENCE BV SURFACE SCIENCE, 515 (2-3) Article number PII S0039-6028(02)01978-7 , pp. 553-566.
- . (2000) 'The adsorption and decomposition of chromium hexacarbonyl on Pd(100)'. ELSEVIER SCIENCE BV SURFACE SCIENCE, 464 (1), pp. L667-L672.
- . (1999) 'Amorphous alloys as secondary standards for electron spin polarimetry'. IOP PUBLISHING LTD MEASUREMENT SCIENCE & TECHNOLOGY, 10 (4), pp. 269-274.
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(1997) 'Reflection absorption IR studies of vibrational energy transfer processes and adsorption energetics'. ROYAL SOC CHEMISTRY JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 93 (13), pp. 2315-2322.doi: 10.1039/a700208d
Conference papers
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(2011) 'Substantial temperature dependence of transverse electron g*-factor in lead chalcogenide multi-quantum wells'. American Institute of Physics AIP Conference Proceedings, Blacksburg, USA: 15TH INTERNATIONAL CONFERENCE ON NARROW GAP SYSTEMS 1416, pp. 178-180.doi: 10.1063/1.3671728
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(2011) 'Manipulation of spin dynamics in semiconductor structures by orientation of small external magnetic field'. American Institute of Physics AIP Conference Proceedings, Seoul, South Korea: ICPS2010, 30th International Conference on the Physics of Semiconductors 1399, pp. 657-658.doi: 10.1063/1.3666548
- . (2010) 'Carbon nanotube field effect transistor measurements in vacuum'. IEEE International Conference on Semiconductor Electronics, Proceedings, ICSE, , pp. 224-228.
- . (2008) 'Density and well-width dependence of the spin relaxation in n-InSb/AlInSb quantum wells'. SPRINGER NARROW GAP SEMICONDUCTORS 2007, Guildford, ENGLAND: 13th International Conference on Narrow Gap Semiconductors 119, pp. 19-21.
- . (2008) 'Gate dependence of spin-splitting in an InSb/InAlSb quantum well'. SPRINGER NARROW GAP SEMICONDUCTORS 2007, Guildford, ENGLAND: 13th International Conference on Narrow Gap Semiconductors 119, pp. 3-5.
- . (2008) '(S)TEM Characterisation of InAs/MgO/Co Multilayers'. SPRINGER-VERLAG BERLIN MICROSCOPY OF SEMICONDUCTING MATERIALS 2007, Univ Cambridge, Cambridge, ENGLAND: 15th Conference on Microscopy of Semiconducting Materials 120, pp. 153-156.
- . (2007) 'Improved geometric control of the high-field linear magnetoresistance by metallic bridges in InSb arrays'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 1383-1384.
- . (2007) 'Oblique Hanle measurements of InAs/GaAs quantum dot spin-light emitting diodes'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 1289-1290.
- . (2007) 'Inherent magnetoresistance and surface morphology of InSb thin films'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 561-562.
- . (2007) 'Planar Andreev spectroscopy in InAs'. AMER INST PHYSICS Physics of Semiconductors, Pts A and B, Vienna, AUSTRIA: 28th International Conference on the Physics of Semiconductors (ICPS-28) 893, pp. 1281-1282.
- . (2004) 'InSb epilayers on GaAs(100) for spintronic and magneto-resistive sensor applications'. ELSEVIER SCIENCE BV PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES, UNIV BUFFALO, BUFFALO, NEW YORK: 11th International Conference on Narrow Gap Semiconductors 20 (3-4), pp. 216-219.
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(2004) 'Spin relaxation in InSb and InAs by 1-and 2-colour spectroscopy with free electron and solid state lasers'. IEEE CONFERENCE DIGEST OF THE 2004 JOINT 29TH INTERNATIONAL CONFERENCE ON INFRARED AND MILLIMETER WAVES AND 12TH INTERNATIONAL CONFERENCE ON TERAHERTZ ELECTRONICS, Univ Karlsruhe, Karlsruhe, GERMANY: Joint 29th International Conference on Infrared and Millimeter Waves/12th International Conference on Terahertz Electronics, pp. 207-208.Full text is available at: http://epubs.surrey.ac.uk/1757/
- . (2004) 'Spin lifetimes in narrow gap semiconductors measured with free-electron and solid-state lasers'. ELECTROCHEMICAL SOCIETY INC STATE-OF-THE-ART PROGRAM ON COMPOUND SEMICONDUCTORS XL (SOTAPOCS XL) AND NARROW BANDGAP OPTOELECTRONIC MATERIALS AND DEVICES II, San Antonio, TX: 40th State-of-the-Art Program on Compound Semiconductors (SOTAPOCS XL)/2nd Narrow Bandgap Optoelectronic Materials and Devices Symposium 2004 (2), pp. 253-258.
- . (1997) 'A study of adsorbate vibrations at cryogenic temperatures'. WORLD SCIENTIFIC PUBL CO PTE LTD SURFACE REVIEW AND LETTERS, UNIV AIX MARSEILLE, AIX PROVENCE, FRANCE: 5th International Conference on the Structure of Surfaces (ICSOS-5) 4 (6), pp. 1365-1370.
Books
- . (2008) Narrow gap semiconductors 2007. Springer
Teaching
Year 2
Module co-ordinator of "From Atoms to Lasers"
Leader of Semester 2 Undergraduate Laboratory.
Professional Training visiting tutor
MSc Radiation Detection Instrumention
Introduction of LabView
Departmental Duties
Postgraduate Tutor for Advanced Technology Institute
Coordinator and founder of the National Instruments Academy in the Faculty of Engineering and Physical Sciences, providing LabView training for post-graduate researchers and research staff.
