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X-ray Characterization of Crystalline Defects and Strains in Thin Films

Davor Balzar 

University of Denver, 2112 E Wesley Ave, Denver 80208, United States

Abstract

Sensing materials' properties at nanoscale presents new challenges for diffraction techniques. As much as novel synchrotron and neutron sources made measurements at small scales feasible, analyzing the results requires improved models in order to accurately extract properties of interest. One of the most serious impediments to improving the methodology relates to sometimes orthogonal approaches to data analysis. A comparative analysis of some widely used approaches will be given with the emphasis on the use of full-powder-pattern fitting techniques, such as Rietveld refinement, to obtain information about coherently diffracting domain size, strain, defect densities, and residual stress. A topic of considerable interest is tungsten thin films used in the fabrication of photon number-resolving transition-edge sensor (TES) and arrays of TES detectors for astronomical and quantum information applications. Tungsten can form in one of two crystal structures: alpha (bcc), with a superconducting transition temperature (Tc) of 15 mK, and beta (A15), with a Tc between 1 and 4 K. Films with intermediate Tcs are composed of both alpha and beta phases. Variation of deposition conditions, and also the choice of the underlayer/coating for equal deposition conditions, affect the Tcs of tungsten films. We have used both laboratory and synchrotron (APS high-energy 6-ID-MU beamline at 52 keV in transmission geometry) X-ray diffraction to determine the structure of tungsten thin films and film stress at both room temperature and 8 K.

 

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Related papers

Presentation: Invited at E-MRS Fall Meeting 2007, Symposium H, by Davor Balzar
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-15 02:36
Revised:   2009-06-07 00:44