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WW10.10 - X-Ray Micro-Beam Characterisation of Lattice Rotations and Distortions Due to a Single Dislocation 
April 25, 2014   4:45pm - 5:00pm

Understanding and controlling the behaviour of dislocations is crucial for a wide range of applications, from nano-electronics and solar cells to structural engineering alloys. Transmission electron microscopy (TEM) revolutionised materials science through its ability to directly image dislocations but is limited to applications involving thin, electron transparent samples. The diffraction of more penetrating X-rays provides a perfect complement. However, thus far the quantitative measurement of the strain fields due to individual dislocations, particularly in the bulk, using micro-diffraction has remained elusive. Here we report the first characterisation of a single dislocation in a freestanding 130 nm thick GaAs/In0.2Ga0.8As/GaAs membrane by synchrotron X-ray micro-beam Laue diffraction. A thin sample was chosen to allow a direct comparison with TEM images of dislocations within this sample. Our experimental X-ray measurements of lattice rotations and strains agree with textbook anisotropic elasticity solutions for single dislocations, providing one of few experimental validations of this fundamental theory. However, unlike TEM, our measurements are not limited to thin samples. Indeed, based on the experimental uncertainty in our measurements, we predict that 3D measurements of lattice strains and rotations due to individual dislocations in the material bulk are feasible provided a sufficiently small focal spotsize of the polychromatic X-ray probe beam can be achieved. These findings have important implications for the in-situ study of dislocation structure formation, self-organisation and evolution in the bulk.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis