Dr Steven Clowes

Senior Lecturer, Postgraduate Research Director for ATI

Qualifications: MSc, PhD

Email:
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
2007-2012 EPSRC Advanced Research Fellow, ATI, University of Surrey
2012 Lecturer, Department of Physics, University of Surrey
2014 Senior Lecturer, Department of Physics, University of Surrey

Research Interests

  • Study of spin dependent electron transport in semiconductor devices using optically orientated photo-conductivity measurements.
  • Ultrafast spin dynamics in high spin-orbit coupled two dimensional systems.
  • III-V bismides for spintronic applications.
  • Quantum control of dopants in silicon for quantum information processing.
  • Direct magnetic measurement of optically induced magnetism is doped nanocrystals.

 

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

  • Murdin BN, Li J, Pang ML, Bowyer ET, Litvinenko KL, Clowes SK, Engelkamp H, Pidgeon CR, Galbraith I, Abrosimov NV, Riemann H, Pavlov SG, Hübers HW, Murdin PG. (2013) 'Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars.'. Nat Commun, England: 4

    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.

  • Li J, Litvinenko KL, Clowes SK, Gilbertson AM, Cohen LF. (2012) 'Observation of spin dependent photocoductivity in InSb quantum well nanowires'. Applied Physics Letters, 101 (15)

    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.

  • Nordin MN, Li J, Clowes SK, Curry RJ. (2012) 'Temperature dependent optical properties of PbS nanocrystals.'. Nanotechnology, England: 23 (27)

    Abstract

    A comprehensive study of the optical properties of PbS nanocrystals (NCs) is reported that includes the temperature dependent absorption, photoluminescence (PL) and PL lifetime in the range of 3-300 K. The absorption and PL are found to display different temperature dependent behaviour though both redshift as temperature is reduced. This results in a temperature dependent Stokes shift which increases from ∼75 meV at 300 K with reducing temperature until saturating at ∼130 meV below ∼150 K prior to a small reduction to 125 meV upon cooling from 25 to 3 K. The PL lifetime is found to be single exponential at 3 K with a lifetime of τ(1) = 6.5 μs. Above 3 K biexponential behaviour is observed with the lifetime for each process displaying a different temperature dependence. The Stokes shift is modelled using a three-level rate equation model incorporating temperature dependent parameter values obtained via fitting phenomenological relationships to the observed absorption and PL behaviour. This results in a predicted energy difference between the two emitting states of ∼6 meV which is close to the excitonic exchange energy splitting predicted theoretically for these systems.

  • Li J, Gilbertson AM, Litvinenko KL, Cohen LF, Clowes SK. (2012) 'Transverse focusing of spin-polarized photocurrents'. Physical Review B (Condensed Matter and Materials Physics), 85 Article number 045431

    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.

  • Stachel S, Olbrich P, Zoth C, Hagner U, Stangl T, Karl C, Lutz P, Bel'kov VV, Clowes SK, Ashley T, Gilbertson AM, Ganichev SD. (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
  • Leontiadou MA, Litvinenko KL, Gilbertson AM, Pidgeon CR, Branford WR, Cohen LF, Fearn M, Ashley T, Emeny MT, Murdin BN, Clowes SK. (2011) 'Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures'. JOURNAL OF PHYSICS-CONDENSED MATTER, 23 (3) Article number ARTN 035801
  • Litvinenko KL, Leontiadou MA, Li J, Clowes SK, Emeny MT, Ashley T, Pidgeon CR, Cohen LF, Murdin BN. (2010) 'Strong dependence of spin dynamics on the orientation of an external magnetic field for InSb and InAs'. APPLIED PHYSICS LETTERS, 96 (11) Article number ARTN 111107
  • Magnus F, Clowes SK, Gilbertson AM, Branford WR, Barkhoudarov ED, Cohen LF, Singh LJ, Barber ZH, Blamire MG, Buckle PD, Buckle L, Ashley T, Eustace DA, McComb DW. (2007) 'Electrical characterization of MgO tunnel barriers grown on InAs (001) epilayers'. APPLIED PHYSICS LETTERS, 91 (12) Article number ARTN 122106
  • Itskos G, Harbord E, Clowes SK, Clarke E, Van Dorpe P, Van Roy W, Cohen LF, Murray R, Jantsch W, Schaffler F. (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.
  • Itskos G, Harbord E, Clowes SK, Clarke E, Cohen LF, Murray R, Van Dorpe P, Van Roy W. (2006) 'Oblique Hanle measurements of InAs/GaAs quantum dot spin-light emitting diodes'. APPLIED PHYSICS LETTERS, 88 (2) Article number ARTN 022113

Journal articles

  • Stachel S, Budkin GV, Hagner U, Bel'kov VV, Glazov MM, Tarasenko SA, Clowes SK, Ashley T, Gilbertson AM, Ganichev SD. (2014) 'Cyclotron-resonance-assisted photon drag effect in InSb/InAlSb quantum wells excited by terahertz radiation'. PHYSICAL REVIEW B, 89 (11) Article number ARTN 115435
  • Murdin BN, Li J, Pang ML, Bowyer ET, Litvinenko KL, Clowes SK, Engelkamp H, Pidgeon CR, Galbraith I, Abrosimov NV, Riemann H, Pavlov SG, Hübers HW, Murdin PG. (2013) 'Si:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars.'. Nat Commun, England: 4

    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.

  • Li J, Litvinenko KL, Clowes SK, Gilbertson AM, Cohen LF. (2012) 'Observation of spin dependent photocoductivity in InSb quantum well nanowires'. Applied Physics Letters, 101 (15)

    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.

  • Nordin MN, Li J, Clowes SK, Curry RJ. (2012) 'Temperature dependent optical properties of PbS nanocrystals.'. Nanotechnology, England: 23 (27)

    Abstract

    A comprehensive study of the optical properties of PbS nanocrystals (NCs) is reported that includes the temperature dependent absorption, photoluminescence (PL) and PL lifetime in the range of 3-300 K. The absorption and PL are found to display different temperature dependent behaviour though both redshift as temperature is reduced. This results in a temperature dependent Stokes shift which increases from ∼75 meV at 300 K with reducing temperature until saturating at ∼130 meV below ∼150 K prior to a small reduction to 125 meV upon cooling from 25 to 3 K. The PL lifetime is found to be single exponential at 3 K with a lifetime of τ(1) = 6.5 μs. Above 3 K biexponential behaviour is observed with the lifetime for each process displaying a different temperature dependence. The Stokes shift is modelled using a three-level rate equation model incorporating temperature dependent parameter values obtained via fitting phenomenological relationships to the observed absorption and PL behaviour. This results in a predicted energy difference between the two emitting states of ∼6 meV which is close to the excitonic exchange energy splitting predicted theoretically for these systems.

  • Li J, Gilbertson AM, Litvinenko KL, Cohen LF, Clowes SK. (2012) 'Transverse focusing of spin-polarized photocurrents'. Physical Review B (Condensed Matter and Materials Physics), 85 Article number 045431

    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.

  • Stachel S, Olbrich P, Zoth C, Hagner U, Stangl T, Karl C, Lutz P, Bel'kov VV, Clowes SK, Ashley T, Gilbertson AM, Ganichev SD. (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
  • Abdul Rahman AT, Bräuer-Krisch E, Brochard T, Adamovics J, Clowes SK, Bradley D, Doran SJ. (2011) 'Sophisticated test objects for the quality assurance of optical computed tomography scanners.'. Phys Med Biol, England: 56 (14), pp. 4177-4199.

    Abstract

    Optical computed tomography (CT), in conjunction with radiochromic gels and plastics, shows great potential for radiation therapy dose verification in 3D. However, an effective quality assurance (QA) regime for the various scanners currently available still remains to be developed. We show how the favourable properties of the PRESAGE® radiochromic polymer may be exploited to create highly sophisticated QA phantoms. Five 60 mm diameter cylindrical PRESAGE® samples were irradiated using the x-ray microbeam radiation therapy facility on the ID-17 biomedical beamline at the European Synchrotron Radiation Facility. Samples were then imaged on the University of Surrey parallel-beam optical CT scanner. The sample irradiations were designed to allow a variety of tests to be performed, including assessments of linearity, modulation transfer function (three independent measurements), geometric distortion and the effect of treatment fractionation. It is clear that, although the synchrotron method produces extremely high-quality test objects, it is not practical on a routine basis, because of its reliance on a highly specialized radiation source. Hence, we investigated a second possibility: three PRESAGE® samples were illuminated with ultraviolet light of wavelength 365 nm, using cheap masks created by laser-printing patterns onto overhead projector acetate sheets. There was good correlation between optical densities measured by the CT scanner and the expected UV 'dose' delivered. The results are encouraging and a proposal is made for a scanner test regime based on calibrated and well-characterized PRESAGE® samples.

  • Leontiadou MA, Litvinenko KL, Gilbertson AM, Pidgeon CR, Branford WR, Cohen LF, Fearn M, Ashley T, Emeny MT, Murdin BN, Clowes SK. (2011) 'Experimental determination of the Rashba coefficient in InSb/InAlSb quantum wells at zero magnetic field and elevated temperatures'. JOURNAL OF PHYSICS-CONDENSED MATTER, 23 (3) Article number ARTN 035801
  • Litvinenko KL, Leontiadou MA, Li J, Clowes SK, Emeny MT, Ashley T, Pidgeon CR, Cohen LF, Murdin BN. (2010) 'Strong dependence of spin dynamics on the orientation of an external magnetic field for InSb and InAs'. APPLIED PHYSICS LETTERS, 96 (11) Article number ARTN 111107
  • Magnus F, Yates KA, Clowes SK, Miyoshi Y, Bugoslavsky Y, Cohen LF, Aziz A, Burnell G, Blamire MG, Josephs-Franks PW. (2008) 'Interface properties of Pb/InAs planar structures for Andreev spectroscopy'. APPLIED PHYSICS LETTERS, 92 (1) Article number ARTN 012501
  • Magnus F, Clowes SK, Gilbertson AM, Branford WR, Barkhoudarov ED, Cohen LF, Singh LJ, Barber ZH, Blamire MG, Buckle PD, Buckle L, Ashley T, Eustace DA, McComb DW. (2007) 'Electrical characterization of MgO tunnel barriers grown on InAs (001) epilayers'. APPLIED PHYSICS LETTERS, 91 (12) Article number ARTN 122106
  • Gilbertson AM, Orr JMS, Buckle PD, Clowes S, Fearn M, Storey CJ, Buckle L, Cohen LF, Ashley T. (2007) 'Low-temperature Schottky barrier tunneling in InSb/InxAl1-xSb quantum well heterostructures'. PHYSICAL REVIEW B, 76 (8) Article number ARTN 085306
  • Singh LJ, Oliver RA, Barber ZH, Eustace DA, McComb DW, Clowes SK, Gilbertson AM, Magnus F, Branford WR, Cohen LF, Buckle L, Buckle PD, Ashley T. (2007) 'Preparation of InAs(001) surface for spin injection via a chemical route'. JOURNAL OF PHYSICS D-APPLIED PHYSICS, 40 (10), pp. 3190-3193.
  • Branford WR, Singh LJ, Barber ZH, Kohn A, Petford-Long AK, Van Roy W, Magnus F, Morrison K, Clowes SK, Bugoslavsky YV, Cohen LF. (2007) 'Temperature insensitivity of the spin-polarization in Co2MnSi films on GaAs (001)'. NEW JOURNAL OF PHYSICS, 9 Article number PII S1367-2630(07)34448-0
  • Zhang T, Harris JJ, Branford WR, Clowes SK, Cohen LF, Solin SA. (2006) 'Exploration of the inherent magnetoresistance in InSb thin films'. SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 21 (12), pp. 1543-1546.
  • Litvinenko KL, Murdin BN, Allam J, Pidgeon CR, Bird M, Morris K, Branford W, Clowes SK, Cohen LF, Ashley T, Buckle L. (2006) 'Spin relaxation in n-InSb/AlInSb quantum wells'. NEW JOURNAL OF PHYSICS, 8 Article number PII S1367-2630(06)15617-7
  • Murdin BN, Litvinenko K, Clarke DG, Pidgeon CR, Murzyn P, Phillips PJ, Carder D, Berden G, Redlich B, van der Meer AF, Clowes S, Harris JJ, Cohen LF, Ashley T, Buckle L. (2006) 'Spin relaxation by transient monopolar and bipolar optical orientation.'. Phys Rev Lett, United States: 96 (9)

    Abstract

    We have used two-color time-resolved spectroscopy to measure the relaxation of electron spin polarizations in a bulk semiconductor. The circularly polarized pump beam induces a polarization either by direct excitation from the valence band, or by free-carrier (Drude) absorption when tuned to an energy below the band gap. We find that the spin relaxation time, measured with picosecond time resolution by resonant induced Faraday rotation in both cases, increases in the presence of photogenerated holes. In the case of the material chosen, n-InSb, the increase was from 14 to 38 ps.

  • Itskos G, Harbord E, Clowes SK, Clarke E, Cohen LF, Murray R, Van Dorpe P, Van Roy W. (2006) 'Oblique Hanle measurements of InAs/GaAs quantum dot spin-light emitting diodes'. APPLIED PHYSICS LETTERS, 88 (2) Article number ARTN 022113
  • Zhang T, Harris JJ, Branford WR, Bugoslavsky YV, Clowes SK, Cohen LF, Husmann A, Solin SA. (2006) 'Tuning the inherent magnetoresistance of InSb thin films'. APPLIED PHYSICS LETTERS, 88 (1) Article number ARTN 012110
  • Zhang T, Harris JJ, Clowes SK, Debnath M, Bennett A, Cohen LF, Lyford T, Fewster PF. (2005) 'Evidence for dislocation-related amphoteric behaviour of Si dopant in high-mobility InSb thin films'. SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 20 (12), pp. 1153-1156.
  • Murdin BN, Litvinenko K, Allam J, Pidgeon CR, Bird M, Morrison K, Zhang T, Clowes SK, Branford WR, Harris J, Cohen LF. (2005) 'Temperature and doping dependence of spin relaxation in n-InAs'. PHYSICAL REVIEW B, 72 (8) Article number ARTN 085346
  • Branford WR, Husmann A, Solin SA, Clowes SK, Zhang T, Bugoslavsky YV, Cohen LF. (2005) 'Geometric manipulation of the high-field linear magnetoresistance in InSb epilayers on GaAs(001)'. APPLIED PHYSICS LETTERS, 86 (20) Article number ARTN 202116
  • Bugoslavsky Y, Miyoshi Y, Clowes SK, Branford WR, Lake M, Brown I, Caplin AD, Cohen LF. (2005) 'Possibilities and limitations of point-contact spectroscopy for measurements of spin polarization'. PHYSICAL REVIEW B, 71 (10) Article number ARTN 104523
  • Harris JJ, Zhang T, Branford WR, Clowes SK, Debnath M, Bennett A, Roberts C, Cohen LF. (2004) 'The role of impurity band conduction in the low temperature characteristics of thin InSb films grown by molecular beam epitaxy'. SEMICONDUCTOR SCIENCE AND TECHNOLOGY, 19 (12) Article number PII S0268-1242(04)81234-3 , pp. 1406-1410.
  • Gardelis S, Androulakis J, Migiakis P, Giapintzakis J, Clowes SK, Bugoslavsky Y, Branford WR, Miyoshi Y, Cohen LF. (2004) 'Synthesis and physical properties of arc melted NiMnSb'. JOURNAL OF APPLIED PHYSICS, 95 (12), pp. 8063-8068.
  • Clowes SK, Miyoshi Y, Bugoslavsky Y, Branford WR, Grigorescu C, Manea SA, Monnereau O, Cohen LF. (2004) 'Spin polarization of the transport current at the free surface of bulk NiMnSb'. PHYSICAL REVIEW B, 69 (21) Article number ARTN 214425
  • Zhang T, Clowes SK, Debnath M, Bennett A, Roberts C, Harris JJ, Stradling RA, Cohen LF, Lyford T, Fewster PF. (2004) 'High-mobility thin InSb films grown by molecular beam epitaxy'. APPLIED PHYSICS LETTERS, 84 (22), pp. 4463-4465.
  • Branford WR, Roy SB, Clowes SK, Miyoshi Y, Bugoslavsky YV, Gardelis S, Giapintzakis J, Cohen LF. (2004) 'Spin polarisation and anomalous Hall effect in NiMnSb films'. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, pp. E1399-E1401.
  • Clowes SK, Miyoshi Y, Johannson O, Hickey BJ, Marrows CH, Blamire M, Branford WR, Bugoslavsky YV, Cohen LF. (2004) 'Using PCAR to study Cu/Co bilayers'. JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 272, pp. E1471-E1473.
  • Branford WR, Clowes SK, Bugoslavsky YV, Gardelis S, Androulakis J, Giapintzakis J, Grigorescu CEA, Manea SA, Freitas RS, Roy SB, Cohen LF. (2004) 'Thickness dependence of Hall transport in Ni1.15Mn0.85Sb thin films on silicon'. PHYSICAL REVIEW B, 69 (20) Article number ARTN 201305
  • Branford WR, Clowes SK, Syed MH, Bugoslavsky YV, Gardelis S, Androulakis J, Giapintzakis J, Grigorescu CEA, Berenov AV, Roy SB, Cohen LF. (2004) 'Large positive magnetoresistance in nonstoichiometric NiMnSb thin films on silicon'. APPLIED PHYSICS LETTERS, 84 (13), pp. 2358-2360.
  • Fobelets K, Alaudeen A, Ahmad MM, Clowes S, Zhang J. (2004) 'Analysis of steam oxidation of crystalline SIGE using AFM and CABOOM'. Proceedings - Electrochemical Society, 7, pp. 175-179.

    Abstract

    Characterization of the Ge concentration in a SiGe heterojunction for x varying from 5% to 40% in steps of 5% is done by beveling and wet thermal oxidation of the exposed layers. The resulting difference in oxide thickness as a function of Ge concentration is visualized due to light interference. Different Ge concentrations are seen as different colors through an optical microscope. CABOOM - Characterization of the Alloy concentration by Beveling, Oxidation and Optical Microscopy - in combination with AFM - Atomic Force Microscopy, is used as a tool to study the oxidation kinetics of unstrained, crystalline SiGe by wet thermal oxidation.

  • Branford WR, Clowes SK, Bugoslavsky YV, Miyoshi Y, Cohen LF, Berenov AV, MacManus-Driscoll JL, Rager J, Roy SB. (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)'. JOURNAL OF APPLIED PHYSICS, 94 (7), pp. 4714-4716.
  • Goncharova LV, Clowes SK, Fogg RR, Ermakov AV, Hinch BJ. (2002) 'Phosphine adsorption and the production of phosphide phases on Cu(001)'. SURFACE SCIENCE, 515 (2-3) Article number PII S0039-6028(02)01978-7 , pp. 553-566.
  • Clowes SK, Seddon EA, McCash EM. (2000) 'The adsorption and decomposition of chromium hexacarbonyl on Pd(100)'. SURFACE SCIENCE, 464 (1), pp. L667-L672.
  • Seddon EA, Malins AER, Petty M, Crapper MD, Wardell IRM, Hide AK, Hardiman M, Xu YB, Hucknall P, Greig D, Clowes S, McCash EM. (1999) 'Amorphous alloys as secondary standards for electron spin polarimetry'. MEASUREMENT SCIENCE & TECHNOLOGY, 10 (4), pp. 269-274.
  • Cook JC, Clowes SK, McCash EM. (1997) 'Reflection absorption IR studies of vibrational energy transfer processes and adsorption energetics'. JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 93 (13), pp. 2315-2322.

Conference papers

  • Leontiadou MA, Litvinenko KL, Clowes SK, Springholz G, Schwarzl T, Eibelhuber M, Heiss W, Pidgeon CR, Murdin BN. (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.

    Abstract

    We report significant temperature dependence of the transverse electron g∗‐factor in symmetric lead chalcogenide multi‐quantum wells (MQWs). The g∗‐factor values were extracted from the electron Larmor precessions recorded by means of a circularly polarized pump probe technique under the influence of transverse external magnetic field (Voigt geometry) in the temperature range between 10 and 150K. The reported g∗‐factor values are in good agreement with theoretical predictions and available low temperature experimental data. Although temperature tuning of lead salt laser emission wavelengths has been the method of choice in these systems for many years, we demonstrate that temperature can also be used to modulate g∗, and hence the spin lifetime in lead salt QW spintronic devices.

  • Litvinenko K, Leontiadou M, Li J, Bowyer E, Clowes S, Pidgeon CR, Murdin B. (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.

    Abstract

    Electron spin relaxation times have been measured in InSb and InAs quantum wells and epi-layers in a moderate (<4T) external magnetic field by means of time-resolved optical orientation using circularly polarised light. A strong and opposite field dependence of the spin lifetime was observed for longitudinal (Faraday) and transverse (Voigt) configuration. In the Faraday configuration the spin lifetime increases because the DP dephasing process is suppressed. At the high field limit the EY relaxation process dominates, enabling its direct determination. Conversely, in the Voigt configuration an additional efficient spin dephasing mechanism dominates and shortens the electron spin lifetime considerably with B-2. We demonstrate that for narrow gap semiconductors simply changing the direction of the magnetic field of 1T can alter the electron spin lifetime by one order of magnitude.

  • Yahya I, Mustaza SM, Stolojan V, Clowes S, Silva SRP. (2010) 'Carbon nanotube field effect transistor measurements in vacuum'. IEEE International Conference on Semiconductor Electronics, Proceedings, ICSE, , pp. 224-228.

    Abstract

    Three terminal measurements on a carbon nanotube field effect transistor (CNTFET) were carried out in high vacuum and the ambient, and its performance compared. The on-off current ratio, I/I, were 10 and 10 for devices operated in high vacuum and in ambient air, respectively. Here, we show that the conversion of p-type to ambipolar behavior may largely be attributed to the O in ambient doping the single walled carbon nanotubes (SWCNTs) in the active channel which consists of bundles of SWCNTs. Switching behaviour of these devices, with respect to constituent types of SWCNTs in the bundles will be discussed. © 2010 IEEE.

  • Branford WR, Gilbertson AM, Buckle PD, Buckle L, Ashley T, Magnus F, Clowes SK, Harris JJ, Cohen LF, Murdin BN, Clowes S. (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.
  • Eustace DA, McComb DW, Buckle L, Buckle P, Ashley T, Singh LJ, Barber ZH, Gilbertson AM, Branford WR, Clowes SK, Cohen LF, Cullis AG, Midgley PA. (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.
  • Litvinenko KL, Murdin BN, Clowes SK, Nikzad L, Allam J, Pidgeon CR, Branford W, Cohen LF, Ashley T, Buckle L, Murdin BN, Clowes S. (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.
  • Magnus F, Burnell G, Miyoshi Y, Yates KA, Bugoslavsky Y, Clowes SK, Josephs-Franks PW, Blamire MG, Cohen LF, Jantsch W, Schaffler F. (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.
  • Itskos G, Harbord E, Clowes SK, Clarke E, Van Dorpe P, Van Roy W, Cohen LF, Murray R, Jantsch W, Schaffler F. (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.
  • Zhang T, Harris JJ, Branford WR, Clowes SK, Cohen LF, Solin SA, Jantsch W, Schaffler F. (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.
  • Clowes SK, Branford WR, Gilbertson AM, Zhang T, Buckle L, Husmann A, Solin SA, Cohen LF, Jantsch W, Schaffler F. (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.
  • Murdin BN, Merrick M, Litvinenko K, Murzyn P, Phillips PJ, Pidgeon CR, Zhang T, Clowes SK, Cohen LF, Buckle P, Ashley T, Buckley DN, Chang PC, Fox PD, Chan WK, Shiojima K. (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.
  • Zhang T, Debnath M, Clowes SK, Branford WR, Bennett A, Roberts C, Cohen LF, Stradling RA. (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.
  • Pidgeon CR, Murzyn P, Phillips PJ, Murdin BN, Litvinenko K, Merrick M, Cohen LF, Zhang T, Clowes SK, Buckle P, Ashley T, Thumm M, Wiesbeck W. (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.
  • Camplin JP, Clowes SK, Cook JC, McCash EM. (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

  • Murdin BN, Clowes SK. (2008) Narrow gap semiconductors 2007. Springer

    Abstract

    This book contains the invited and contributed papers which were presented at this meeting and serves to provide a broad overview of the current worldwide ...

Teaching

Module co-ordinator - PHY2062 From Atoms to Lasers
Module co-ordinator - PHY2072 Light Lab
Module co-ordinator - PHY3053 LabView for Researchers
Lead for level 2 undergraduate laboratory.

Departmental Duties

Postgraduate Research Director for Advanced Technology Institute.
Programme Director for Physics with Quantum Technologies undergraduate course.
Faculty representative of University of Surrey Athena Swan Self-Assessment Team.
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.

Past and Current Grants

£675,777 EPSRC (PI)‘Non-magnetic semiconductor spintronics’, Oct 2007- Sept 2012
£196,953(CI) EPSRC ‘Silicon based spintronics’, Oct 2009-Sept 2012,
£106,044 Leverhulme Trust (CI), ‘Direct magnetic measurement of excitonic induced magnetization in colloidal nanocrystals’ Nov 2011-Nov 2013
£54,639 TSB (PI) Short KTP with Plastipack Ltd., July 2012-July 2013.
£20,024 EPSRC (PI) Impact Acceleration Account, July 2013-Jun 2014
£230,000 TSB (PI) Classic KTP with Plastipack Ltd July 2014-July 2017

 

Page Owner: sc0019
Page Created: Monday 10 August 2009 11:36:19 by lb0014
Last Modified: Wednesday 15 October 2014 14:37:44 by sc0019
Expiry Date: Wednesday 10 November 2010 11:35:34
Assembly date: Tue Dec 16 22:24:23 GMT 2014
Content ID: 11662
Revision: 10
Community: 1256