Stuart Cavill
Nanoscience
Stuart Cavill is the beamline scientist on the Nanoscience Beamline I06. His main interest is in the physics and chemistry of nanostructured material. Before joining Diamond, he was a research fellow in the Nanoscience group at Nottingham University where he undertook research on the optical and electronic properties of low dimensional semiconductors.
Email: Stuart Cavill
Tel: +44 (0) 1235 778262
Beamline I06: Nanoscience
Key Research Areas
Low dimensional systems, Ultrafast electron dynamics, micro-spectroscopy, nanotechnology.
Current Research Interests
Semiconductor hetero- and nano-structures are a very active area of research because of the novel physical phenomena they display. For example Si nanostructures in the form of porous silicon and silicon nanowires emit light in the visible upon photo-excitation. Bulk silicon on the other hand does not.
Devices based on these materials contain carriers which are subject to a strong spatiotemporal gradient of the electric field, rendering the validity of our classical description of carrier dynamics questionable. Recent work on relaxation dynamics in these materials has concentrated on the use of ultrafast optical spectroscopy to provide insights into carrier dynamics before an equilibrium state is reached. However, the difficulty of applying ultrafast optical techniques to indirect band-gap materials such as silicon is simply that the momentum-conserving phonon involved in the fundamental optical transition makes it hard to relate observed experimental changes in optical properties to changes in the carrier distribution.
My research has focused on the combined use of x-ray and optical spectroscopies, which provides an ideal tool for studying the electronic structure and optical properties of nanoscale systems and has several advantages over (visible) optical techniques alone. Relaxation dynamics in indirect band-gap materials have been investigated on picosecond time scales by using a pump-probe technique called Time Resolved Two Photon PhotoEmission Spectroscopy which directly probes the excited electron distribution inside the solid. This technique is surface sensitive, which is a key factor in these materials as mid-gap surface states may play an important role in the relaxation and recombination dynamics.
X-ray Excited Optical Luminescence (XEOL) can also be used to provide a further insight into these materials because it allows one to access information that is not attainable from a single technique alone. The XEOL technique is ideally suited for the investigation of light emitting materials, especially when it is conducted at a synchrotron light source, as it uses the elemental specificity of the X-rays at an absorption edge to reveal the chemical nature of the fluorescent sites.
Selected Publications
- "Acoustic phonon-assisted tunneling in GaAs/AlAs superlattices", S. A. Cavill , L. J. Challis , A. J. Kent , F. F. Ouali , A. V. Akimov , and M. Henini Phys. Rev. B 66, 235320 (2002)
- "Carrier - Phonon interactions in semiconductor quantum dots and wires", S. A. Cavill, P. Hawker, and A. J. Kent, in Electron-Phonon Interactions in Low-dimensional Structures, L. J. Challis, Ed.: Oxford University Press.
- "Phonon emission by photoexcited carriers in InGaN/GaN multiple quantum wells,"A. V. Akimov, S. A. Cavill, A. J. Kent, N. M. Stanton, T. Wang, and S. Sakai, Journal of Physics-Condensed Matter.
- "Imaging Phonon Drag in Gallium Nitride", N. M. Stanton, A. V. Akimov, A. J. Kent, S. A. Cavill, T. S. Cheng, C.T. Foxon, Applied Physics Letters