Projects per year
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.
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.
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.
1/10/20 → 1/04/24
Project: Research Studentship - Internally Allocated
Advances in electron channelling contrast imaging and electron backscatter diffraction for imaging and analysis of structural defects in the scanning electron microscopeTrager-Cowan, C., Alasmari, A., Avis, W., Bruckbauer, J., Edwards, P. R., Hourahine, B., Kraeusel, S., Kusch, G., Jablon, B. M., Johnston, R., Martin, R. W., McDermott, R., Naresh-Kumar, G., Nouf-Allehiani, M., Pascal, E., Thomson, D., Vespucci, S., Mingard, K., Parbrook, P. J., Smith, M. D. & 17 others, , 5 Aug 2020, In: IOP Conference Series: Materials Science and Engineering. 891, 1, 11 p., 012023.
Research output: Contribution to journal › Conference article › peer-reviewOpen AccessFile5 Downloads (Pure)
AlN overgrowth of nano-pillar-patterned sapphire with different offcut angle by metalorganic vapor phase epitaxyWalde, S., Hagedorn, S., Coulon, P-M., Mogilatenko, A., Netzel, C., Weinrich, J., Susilo, N., Ziffer, E., Matiwe, L., Hartmann, C., Kusch, G., Alasmari, A., Naresh-Kumar, G., Trager-Cowan, C., Wernicke, T., Straubinger, T., Bickermann, M., Martin, R. W., Shields, P. A., Kneissl, M. & 1 others, , 1 Feb 2020, In: Journal of Crystal Growth. 531, 6 p., 125343.
Research output: Contribution to journal › Article › peer-reviewOpen AccessFile5 Citations (Scopus)2 Downloads (Pure)
Data for: "Metrology of crystal defects through intensity variations in secondary electrons from the diffraction of primary electrons in a scanning electron microscope"
Gunasekar, N. (Creator), Alasmari, A. M. A. (Contributor), Kusch, G. (Contributor), Edwards, P. (Contributor), Martin, R. (Contributor), Trager-Cowan, C. (Contributor) & Mingard, K. (Contributor), University of Strathclyde, 8 Apr 2020
Data for: "AlN overgrowth of nano-pillar-patterned sapphire with different offcut angle by metalorganic vapor phase epitaxy"
Walde, S. (Creator), Hagedorn, S. (Creator), Coulon, P. (Creator), Mogilatenko, A. (Contributor), Netzel, C. (Contributor), Weinrich, J. (Contributor), Susilo, N. (Contributor), Ziffer, E. (Contributor), Matiwe, L. (Contributor), Hartmann, C. (Contributor), Kusch, G. (Creator), Alasmari, A. M. A. (Creator), Gunasekar, N. (Contributor), Trager-Cowan, C. (Creator), Wernicke, T. (Contributor), Straubinger, T. (Contributor), Bickermann, M. (Contributor), Martin, R. (Contributor), Shields, P. A. (Contributor), Kneissl, M. (Contributor) & Weyers, M. (Contributor), University of Strathclyde, 25 Nov 2019
Invited Talk: EMAG 2020 Microscopy Enabled by Direct Electron Detection (on-line). Title: Direct electron detectors for diffraction studies in the scanning electron microscope
Carol Trager-Cowan (Speaker)6 Jul 2020 → 8 Jul 2020
Activity: Talk or presentation types › Invited talk
Invited Talk: SPIE Photonics West Conference: Gallium Nitride Materials and Devices XV, US, February 2020. Title: Visualization of defects in nitride semiconductors by electron channeling.
Carol Trager-Cowan (Speaker)4 Feb 2020
Activity: Talk or presentation types › Invited talk