Local structure of nanopowders of refractory nitrides used to increase the critical current of high-temperature superconductors
The effect of dispersivity on the local-structure features in ZrN nanocrystals has been investigated by X-ray absorption (EXAFS) spectroscopy. The Debye-Waller factors and bond lengths have been determined for Zr-N and Zr-Zr coordination spheres. It is found that a decrease in the nanoparticle size leads to an increase in the static Debye-Waller factor for the Zr-Zr bond. The scale of changes is comparable with the increase in the Debye-Waller factor upon heating from 15 to 77 K.
Extraction of the fine structure from x-ray absorption spectra
We propose two methods for obtaining the atomic-like background for the x-ray absorption fine structure (XAFS): the methods of smoothing spline and of Bayesian smoothing. Both are capable of using the prior information, calculated or experimental, about the background. The XAFS signals obtained by these techniques are shown to be significantly corrected in comparison with standard methods. The method of Bayesian smoothing is the only method that gives the errors of approximation of the atomic-like background by an artificial smooth function. These errors are shown to be the main source of the uncertainty of the XAFS function.
Concept and development of combinatorial laser MBE for oxide electronics
Abstract As a treasure island of new functional materials, metal oxides attract rapidly growing interest as exemplified by the high- T c cuprates and quantum functional perovskites. The development of new efficient instrument to construct artificially designed crystal lattices and hetro-junctions is considered to facilitate the systematic exploration of new materials, properties, and application of oxides. Powerful tools for this purpose are designed based on combinatorial chemistry and molecular layer epitaxy. With focuses on the concept and method, this novel technology of combinatorial laser MBE is reported and demonstrated to be useful for high throughput synthesis of functional oxide thin films and layered lattices.