Shear at twin domain boundaries in YBa2Cu3O7-x.

The microstructure and strain state of twin domains in YBa2Cu3O7-x are discussed based upon synchrotron white-beam x-ray microdiffraction measurements. Intensity variations of the fourfold twin splitting of Laue diffraction peaks are used to determine the twin domain structure. Strain analysis shows that interfaces between neighboring twin domains are strained in shear, whereas the interior of these domains are regions of low strain. These measurements are consistent with the orientation relationships of twin boundaries within and across domains and show that basal plane shear stresses can exceed 100 MPa where twin domains meet. Our results support stress field pinning of magnetic flux vortices by twin domain boundaries.

Local plasticity of Al thin films as revealed by x-ray microdiffraction.

Grain-to-grain interactions dominate the plasticity of Al thin films and establish effective length scales smaller than the grain size. We have measured large strain distributions and their changes under plastic strain in 1.5-microm-thick Al 0.5% Cu films using a 0.8-microm-diameter white x-ray probe at the Advanced Light Source. Strain distributions arise not only from the distribution of grain sizes and orientation, but also from the differences in grain shape and from stress environment. Multiple active glide plane domains have been found within single grains. Large grains behave like multiple smaller grains even before a dislocation substructure can evolve.

Scanning X-ray microdiffraction with submicrometer white beam for strain/stress and orientation mapping in thin films.

Scanning X-ray microdiffraction (microSXRD) combines the use of high-brilliance synchrotron sources with the latest achromatic X-ray focusing optics and fast large-area two-dimensional-detector technology. Using white beams or a combination of white and monochromatic beams, this technique allows for the orientation and strain/stress mapping of polycrystalline thin films with submicrometer spatial resolution. The technique is described in detail as applied to the study of thin aluminium and copper blanket films and lines following electromigration testing and/or thermal cycling experiments. It is shown that there are significant orientation and strain/stress variations between grains and inside individual grains. A polycrystalline film when investigated at the granular (micrometer) level shows a highly mechanically inhomogeneous medium that allows insight into its mesoscopic properties. If the microSXRD data are averaged over a macroscopic range, results show good agreement with direct macroscopic texture and stress measurements.

CHESS: The New Synchrotron Radiation Facility at Cornell.

A new synchrotron radiation laboratory, CHESS, will soon be completed at Cornell University. The facility will operate in a mode parasitic to high energy physics experiments on the new 8-billion-electron-volt electron-positron storage ring (CESR) at Cornell. Electron and positron beams have already been stored and the first photons have been extracted. When completed, the laboratory will be available to the scientific community nationally and will provide the most intense tunable source of high energy x-rays in the country.