Corpus Christi College Oxford

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Professor Michael Johnston

Michael Johnston

Fellow and Tutor, Associate Professor (UL) in Physics, Reader in Physics

michael.johnston@ccc.ox.ac.uk

 

Biography

Michael Johnston is a Reader in Physics at the Oxford's Department of Physics and has been a Fellow of Corpus since 2002. Dr Johnston obtained his PhD in Physics from the University of New South Wales (Sydney, Australia) working on how electrons behave in quantum-confined systems. In 1999 he joined the Cavendish Laboratory at the University of Cambridge, where he was instrumental in setting up a new programme of research on the spectroscopy of semiconductors in the far-infrared ("terahertz") region of the electromagnetic spectrum. On arriving at Oxford in 2002 he established and currently leads a research group specialising in terahertz photonics and spectroscopy. He has made an important contribution towards understanding the emission of terahertz radiation from semiconductors, developed new photonic devices and is an expert on electron dynamics in semiconductor nanostructures.

Research

Dr Johnston's research encompasses technology, spectroscopy and theoretical modelling. To date he has published over 40 papers in the fields of ultra-fast and infrared optics. In 2002 he developed a comprehensive theory of the emission of terahertz (THz) radiation from semiconductors and as a direct consequence of that work he designed, demonstrated and currently holds a patent for a novel high power THz emitter. His research group has a strong background in modelling ultra-fast carrier dynamics, and recently invented, demonstrated and optimised a new type of THz detector that can simultaneously measure the two orthogonal
components of THz electric field as a function of time. This detector allows the complete polarisation state
of a THz pulse to be measured directly. Other recent research highlights include: a study of the charge
dynamics in nanoporous honeycomb structures, an investigation into the localisation of excitons in
Quantum Cascade Lasers, the direct observation of pinned charge density waves in doped nickelates
and the first observation at terahertz frequencies of a photo-induced conformational change in a protein.

Dr Johnston's research is now focused on the electrical properties and nanoscale systems such as nanowires, and molecular semiconductors. Nanowires have the potential to be used as high-speed electronics devices, while molecular semiconductors are showing promise for application in large-area solar cells. He hopes to reveal the fundamental electronic processes that occur in nanoscale media and thereby precipitate the design of better nano-materials and realise new nano-devices.

An introduction to Michael Johnston's research may be found at www-thz.physics.ox.ac.uk

Teaching and supervision

At Corpus Dr Johnston tutors physics at all levels of the undergraduate course. He currently tutors Corpus students in Quantum Mechanics, Atomic Physics, Condensed Matter Physics, Laser Physics and Mathematical Methods. For Oxford Physics his teaching responsibilities include coordinating the 4th year condensed matter physics course and lecturing on band theory and the electronic properties of solids.

Major publications

Simulation of terahertz generation at semiconductor surfaces,
MB Johnston, DM Whittaker, A Corchia, AG Davies, EH Linfield
Phys. Rev. B, 65:165301 (2002) [ doi:10.1103/PhysRevB.65.165301 ]

Polarization-sensitive terahertz detection by multicontact photoconductive receivers,
E Castro-Camus, J Lloyd-Hughes, MB Johnston, MD Fraser, HH Tan, C Jagadish
Appl. Phys. Lett., 86:254102 (2005) [ abstract | pdf | doi:10.1063/1.1951051 ]

Transient terahertz conductivity of GaAs nanowires,
P Parkinson, J Lloyd-Hughes, Q Gao, HH Tan, C Jagadish, MB Johnston, LM Herz
Nano Lett., 7:2162-2165 (2007) [ doi:10.1021/nl071162x ]

Terahertz magnetoconductivity of excitons and electrons in quantum cascade structures,
J Lloyd-Hughes, HE Beere, DA Ritchie, MB Johnston
Phys. Rev. B, 77:125322 (2008) [ doi:10.1103/PhysRevB.77.125322 ]

Conformational changes of photoactive yellow protein monitored by terahertz spectroscopy,
E Castro-Camus, MB Johnston
Chem. Phys. Lett., 455:289-292 (2008) [ doi:10.1016/j.cplett.2008.02.084 ]

Carrier Lifetime and Mobility Enhancement in Nearly Defect-Free Core--Shell Nanowires Measured Using Time-Resolved Terahertz Spectroscopy,
P Parkinson, HJ Joyce, Q Gao, HH Tan, X Zhang, J Zou, C Jagadish, LM Herz, MB Johnston 

Nano Lett., 9:3349-3353 (2009) [ doi:10.1021/nl9016336 ]

Full Publication List: http://www-thz.physics.ox.ac.uk/publications.html

 

 

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