Dr Carol Trager-Cowan

Reader

Physics

Personal statement

I use electron beams to interrogate the structure, defects and light emission from solids. Together with students and colleagues here at Strathclyde and from across the world, I work on new developments and novel applications of the scanning electron microscopy techniques of electron backscatter diffraction, electron channelling contrast imaging and cathodoluminescence imaging. In particular we have developed novel techniques to rapidly and non-destructively analyse defects in nitride semiconductors used for production of UV and visible LEDs and transistor structures.

I currently lecture on solid state physics, electron and scanning probe microscopy and public engagement of research and supervise student projects.

I am also committed to public engagement giving lectures, writing articles, running workshops, quizzes, street busking, leading science street tours and providing kits to schools and am an enthusiastic contributor to the Royal Philosophical Society of Glasgow, the Glasgow Science Festival and to Explorathon (European Researchers Night Scotland). I was elected as a Fellow of the Royal Society of Edinburgh in 2014.

Publications

Design and fabrication of enhanced lateral growth for dislocation reduction in GaN using nanodashes
Le Boulbar E. D., Priesol J. , Nouf-Allehiani M., Naresh-Kumar G., Fox S., Trager-Cowan C., Šatka A., Allsopp D. W. E., Shields P. A.
Journal of Crystal Growth, pp. 30-38, (2017)
http://dx.doi.org/10.1016/j.jcrysgro.2017.02.047
Diffraction effects and inelastic electron transport in angle-resolved microscopic imaging applications
Winkelmann A., Nolze G., Vespucci S., Gunasekar N., Trager-Cowan C., Vilalta-Clemente A., Wilkinson A. J., Vos M.
Journal of Microscopy, (2017)
http://dx.doi.org/10.1111/jmi.12571
Diffractive triangulation of radiative point sources
Vespucci S., Naresh-Kumar G., Trager-Cowan C., Mingard K. P., Maneuski D., O'Shea V., Winkelmann A.
Applied Physics Letters Vol 110, (2017)
http://dx.doi.org/10.1063/1.4978858
Exploring transmission Kikuchi diffraction using a Timepix detector
Vespucci S., Winkelmann A., Mingard K., Maneuski D., O'Shea V., Trager-Cowan C.
Journal of Instrumentation Vol 12, (2017)
http://dx.doi.org/10.1088/1748-0221/12/02/C02075
Cross-correlation based high resolution electron backscatter diffraction and electron channelling contrast imaging for strain mapping and dislocation distributions in InAlN thin films
Vilalta-Clemente A., Naresh-Kumar G., Nouf-Allehiani M., Gamarra P., di Forte-Poisson M.A., Trager-Cowan C., Wilkinson A.J.
Acta Materialia Vol 125, pp. 125-135, (2017)
http://dx.doi.org/10.1016/j.actamat.2016.11.039
Nanoscale fissure formation in AlxGa1–xN/GaN heterostructures and their influence on Ohmic contact formation
Smith M. D., Thomson D., Zubialevich V. Z., Li H., Naresh-Kumar G., Trager-Cowan C., Parbrook P. J.
Physica Status Solidi A Vol 214, (2017)
http://dx.doi.org/10.1002/pssa.201600353

more publications

Research interests

Our research is driven by the need for rapid, non-destructive techniques to reveal and analyse defects in crystalline materials, in particular in nitride semiconductor thin films. III-nitride materials are presently the basis of a fast-growing, multi-billion dollar solid-state lighting industry and commercial AlGaN/GaN electronic devices are now in use in cell phone base stations, satellite communication systems and cable television networks. However, the ultimate performance of these nitride semiconductor based light emitters and electronic devices is limited by extended defects such as threading dislocations (TDs), partial dislocations (PDs), stacking faults (SFs) and grain boundaries (GBs). If we want to develop LEDs to be an effective replacement for the light bulb, or have sufficient power to purify water or develop efficient power electronics for electric vehicles, we need to eliminate these defects as they act as scattering centres for light and charge carriers and give rise to nonradiative recombination and to leakage currents, severely limiting device performance. The first step to this goal is the detection of these defects – we exploit electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD) in a field emission scanning electron microscope to rapidly and non-destructively detect and analyze TDs, PDs, SFs, GBs and map crystal structure, texture, and strain with a lateral and depth resolution on the order of tens of nanometers.

We are involved in both the development and exploitation of the ECCI and EBSD techniques. For example, in collaboration with the Universities of Glasgow and Oxford and the National Physical Laboratory, we are developing new direct electron imaging detectors for electron backscatter diffraction. We are exploiting the digital complementary metal-oxide-semiconductor hybrid pixel detector, Timepix. Timepix is one of the outcomes of an international collaboration (Medipix) hosted at CERN, established to provide a solution for a range of problems in X-ray and gamma-ray imaging in hostile conditions. Using the Timepix allows digital direct electron detection and energy filtering; it enables electron backscatter diffraction patterns to be acquired with reduced noise and increased contrast, and an unprecedented increase in detail is observed in the patterns. This is allowing us to interrogate the fundamental physics of pattern formation and will enable, in the longer term, the application of the EBSD technique to be expanded to materials for which conventional EBSD analysis is not presently practicable. For more information see: Scanning electron microscopy of nitrides: Nanoscale characterisation of nitride semiconductor thin films using EBSD, ECCI, CL and EBIC.

Collaborators

We collaborate with researchers from around the globe including the Universities of Sheffield; Nottingham; Cambridge; Oxford; Bristol; Bath; Tyndall Institute/University College Cork; Aalto University;Technischen Universität Berlin; The National Physical Laboratory and Bruker Nano, Berlin.

Professional activities

UVLED Technology and Application Requirements Workshop
Organiser
22/3/2017
Invited talk at German Physical Society Spring Meeting, Regensburg, Germany. March 2016. Title: Nanocharacterisation of the structural and luminescence properties of materials in the scanning electron microscope
Invited speaker
8/3/2016
Lecture at the Birla Industrial and Technological Museum (BITM), Kolkata, India, January 2015 "Nitrides - The Rainbow Material"
Speaker
18/1/2016
Lecture Series in India as part of "Science and Beyond" organised by the British Council, January 2016. Gave talks on - "Studying structure and light emission in the scanning electron microscope" and "Engaging the Public with Science and Technology – from statues to rainbows"
Invited speaker
10/1/2016
Scientific Organiser of Royal Microscopical Society Electron Backscatter Diffraction Conference, Glasgow, March 2015
Organiser
29/3/2015
Maxwell Lecture at King's College London, March 2015 "Nitrides – The Rainbow Material"
Speaker
2/3/2015

more professional activities

Projects

Enhanced Electron Backscatter Diffraction by Energy Filtered Direct Electron Detection
Trager-Cowan, Carol (Principal Investigator)
Period 01-Oct-2014 - 31-Mar-2018
An EPSRC Life Sciences Interface Doctoral Training Centre for Medical Devices | Dowd, Peter Dylan
Trager-Cowan, Carol (Principal Investigator) Dowd, Peter Dylan (Research Co-investigator)
Period 01-Oct-2006 - 15-Nov-2014
Quantitative non-destructive nanoscale characterisation of advanced materials
Hourahine, Benjamin (Principal Investigator) Edwards, Paul (Co-investigator) Roper, Richard (Co-investigator) Trager-Cowan, Carol (Co-investigator) Gunasekar, Naresh (Researcher)
Period 01-Jun-2017 - 30-Nov-2020
Novel applications of direct electron imaging in the scanning electron microscope
Trager-Cowan, Carol (Principal Investigator)
Period 01-Sep-2016 - 31-Oct-2016
EBSD Research project with NPL
Trager-Cowan, Carol (Principal Investigator)
Period 01-Oct-2015 - 31-Dec-2015
Industrial Case Account 2014 | Pascal, Elena
Trager-Cowan, Carol (Principal Investigator) Hourahine, Benjamin (Co-investigator) Pascal, Elena (Research Co-investigator)
Period 01-Oct-2014 - 01-Oct-2018

more projects