Physics

Dr. Carol Trager-Cowan
University of Strathclyde, Glasgow, UK

About the Speaker: Carol Trager-Cowen is a Reader in the Department of Physics, University of Strathclyde, U.K. She specializes in developments and novel applications of the scanning electron microscopy techniques of electron backscatter diffraction, electron channelling contrast imaging and cathodoluminescence imaging. She actively engages with the public by giving lectures, running workshops and quizzes, leading science street tours, and providing kits to schools. She also writes and commissions articles for the 'Beyond the Lab' section of the MRS Bulletin as the European representative and now chairs the 'Beyond the Lab' Team.

Abstract: The performance requirements for next-generation materials, with applications spanning the aerospace, automotive, oil and gas, electronics and lighting industries, demand pioneering manufacturing techniques combined with innovative characterization tools. The structural properties of materials play a vital role in the performance of critical components and it is important to understand such properties down to the sub-micron scale. For example high temperature operation of gas turbines is affected by the crystal orientation of the nickel-based single-crystal super alloys from which they are made; the optical efficiency and lifetime of UV LEDs is strongly dependent on the type and density of structural defects such as dislocations present in AlGaN thin films.

The novel scanning electron microscopy techniques of electron backscatter diffraction (EBSD); electron channelling contrast imaging (ECCI) and hypespectral cathodoluminescence imaging (CL) can provide complementary information on the structural and luminescence properties of materials rapidly and non-destructively with a spatial resolution of tens of nanometres. EBSD provides orientation, phase and strain analysis, whilst ECCI is used to determine the planar distribution of extended structural defects such as threading dislocations and stacking faults over a large area of a given sample. CL provides information on the influence of crystallographic defects on light emission, either specific defect-related luminescence or dark spot features where carrier recombination at defects is non-radiative. CL can also provide information on the composition of alloy thin films used in the manufacture of light emitting devices, e.g., the AlN content in AlGaN thin films.

In this talk I will describe the EBSD, ECCI and CL techniques and give some examples of their application to real material problems. In particular, I will illustrate the advantages of acquiring coincident EBSD/ECCI/CL data to the understanding of nitride semiconductor structures.