Dr Carol Trager-Cowan

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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 have taught solid state physics; biophysical instrumentation; medical physics; optical; electron and scanning probe microscopy; and public engagement of research. I am presently teaching Introduction to Astronomy; electromagnetism and mechanics. I teach in undergraduate laboratories 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. I am a past Vice President of the Royal Philosophical Society of Glasgow, I am an enthusiastic contributor to 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

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Publications

Imaging threading dislocations and surface steps in nitride thin films using electron backscatter diffraction: Hiller Kieran P, Winkelmann Aimo, Hourahine Ben, Starosta Bohdan, Alasmari Aeshah, Feng Peng, Wang Tao, Parbrook Peter J, Zubialevich Vitaly Z, Hagedorn Sylvia, Walde Sebastian, Weyers Markus, Coulon Pierre-Marie, Shields Philip A, Bruckbauer Jochen, Trager-Cowan Carol; Microscopy and Microanalysis Vol 29, pp. 1879-1888 (2023); https://doi.org/10.1093/micmic/ozad118
Crystalline grain engineered CsPbIBr2 films for indoor photovoltaics: Ghosh Paheli, Bruckbauer Jochen, Trager-Cowan Carol, Jagadamma Lethy Krishnan; Applied Surface Science Vol 592 (2022); https://doi.org/10.1016/j.apsusc.2022.152865
Non-destructive imaging of residual strains in GaN and their effect on optical and electrical properties using correlative light–electron microscopy: Naresh-Kumar G, Edwards P R, Batten T, Nouf-Allehiani M, Vilalta-Clemente A, Wilkinson A J, Le Boulbar E, Shields P A, Starosta B, Hourahine B, Martin R W, Trager-Cowan C; Journal of Applied Physics Vol 131 (2022); https://doi.org/10.1063/5.0080024
Kikuchi pattern simulations of backscattered and transmitted electrons: Winkelmann Aimo, Nolze Gert, Cios Grzegorz, Tokarski Tomasz, Bała Piotr, Hourahine Ben, Trager‐Cowan Carol; Journal of Microscopy Vol 284, pp. 157-184 (2021); https://doi.org/10.1111/jmi.13051
Influence of micro-patterning of the growth template on defect reduction and optical properties of non-polar (11-20) GaN: Bruckbauer Jochen, Gong Yipin, Jiu Ling, Wallace Michael J, Ipsen Anja, Bauer Sebastian, Müller Raphael, Bai Jie, Thonke Klaus, Wang Tao, Trager-Cowan Carol, Martin Robert W; Journal of Physics D: Applied Physics Vol 54 (2020); https://doi.org/10.1088/1361-6463/abbc37
Nanomechanical behaviour of individual phases in WC-Co cemented carbides, from ambient to high temperature: De Luca F, Zhang H, Mingard K, Stewart M, Jablon B M, Trager-Cowan C, Gee M G; Materialia Vol 12 (2020); https://doi.org/10.1016/j.mtla.2020.100713

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Research

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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: Web pages of Semiconductor Spectroscopy and Devices Group.

Collaborators

We collaborate with researchers from around the globe including the Universities of Sheffield; Nottingham; Cambridge; Oxford; Bristol; Bath; Tyndall Institute/University College Cork; Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Poland; CRHEA-CNRS, France; Technischen Universität Berlin; Ferdinand-Braun-Institut, Berlin; Rensselaer Polytechnic Institute, USA; and The National Physical Laboratory.