July 2007 Archives

The 2007 workshop on 'buried' interface science with X-rays and neutrons was held at the Institute of Materials Research, Tohoku University, in Sendai, Japan, on July 22-24, 2007. The workshop was the latest in a series held since 2001; Tsukuba (December 2001), Niigata (September 2002), Nagoya (July 2003), Tsukuba (July 2004), Saitama (March 2005), Yokohama (July 2006), Kusatsu (August 2006) and Tokyo (December 2006). There are increasing demands for sophisticated metrology in order to observe multilayered materials with nano-structures (dots, wires, etc), which are finding applications in electronic, magnetic, optical and other devices. Unlike many other surface-sensitive methods, X-ray and neutron analysis is known for its ability to see even 'buried' function interfaces as well as the surface. It is highly reliable in practice, because the information, which ranges from the atomic to mesoscopic scale, is quantitative and reproducible. However, the method should be upgraded further to cope with more realistic problems in nano sciences and technologies. Current X-ray methods can give atomic-scale information for quite a large area on a scale of mm²-cm². These methods can deliver good statistics for an average, but sometimes it is necessary to analyze a specific part in nano-scale rather than an average structure. In addition, there is a need to see unstable changing structures and related phenomena in order to understand more about the mechanism of the functioning of nano materials. Quick measurements are therefore important. Furthermore, in order to apply the method to a more realistic and complex system, we need some visual understanding to discuss the relationship among the different structures that are present in the same viewing. Therefore, 2D/3D real-space imaging is important. Interpretation of roughness is another significant subject, while combination with grazing-incidence small angle scattering (GISAS) will become much more widespread than before. The use of coherent beams and several other new approaches are also significant. Leading senior academics in this field were invited as commentators, Professors J. Harada (Nagoya University & Rigaku Corporation), S. Kikuta (The University of Tokyo & JASRI) and J. Mizuki (JAEA). The invited speakers from Tohoku University in Sendai, workshop site, Professors K. Takanashi, M. Kawasaki and M. Yanagihara, talked about the hot topic of spintronics, and/or control of 'buried' magnetic interfaces. It was stressed that the use of techniques sensitive to specific interfaces is crucial in analyzing many unsolved problems in this field. The workshop proceedings will be published electronically in Journal of Physics: Conference Series, http://www.iop.org/EJ/journal/1742-6596

The Department of Energy (DOE) in the US granted "Critical Decision 1" (CD-1) status to the National Synchrotron Light Source-II (NSLS-II), which will be a new medium energy storage ring and will replace the existing NSLS which began operations in 1982. This decision assures the facility's location at Brookhaven National Lab. For more about the NSLS-II project, visit the Web page, http://www.bnl.gov/nsls2/

The National Institute for Materials Science, Japan, has announced that the first NIMS Award for recent breakthroughs in materials science and technology has been presented to Professor William H. Butler (Center for Materials for Information Technology, University of Alabama, USA) for the theoretical prediction of giant tunnel magnetoresistance (TMR). Professor Butler performed the first principle calculation on tunnel conductance through MgO(001) single crystal thin film, and theoretically predicted the giant TMR effect of the Fe(100)/MgO/Fe(100) junction for the first time. A giant TMR effect beyond ~500 % has now been realized, which is expected to make a substantial contribution to the development of novel spintronics devices and the creation of a new interdisciplinary field.

The first impression one gets from looking at this book is that it is quite thick and looks heavy, and indeed, a wealth of information on modern XRF is densely packed into its 863 pages. In all, 69 scientists, mainly from Europe but also several from North America, South Africa and Japan have contributed articles on various aspects of the XRF technique; elements of XRF instruments, i.e., X-ray source (Chap. 2), optics (Chap. 3) and detector technologies (Chap. 4), as well as know-how regarding sample preparation (Chap. 6) and many applications (Chap.7 and others). One of the most impressive sections of this book is 'Quantitative Analysis' (Chap. 5) authored by M. Mantler, J. P. Willis, G. R. Lachance, B. A. R. Vrebos, K. E. Mauser, N. Kawahara, R. M. Rousseau and P. N. Brower. The chapter provides a good summary of each historically developed mathematical expression and discusses the issues related to errors and reliability, as well as standardization, which is significant in practical analysis. The intensity of XRF correlates to the concentration of the corresponding element, but also depends on the matrix, i.e., concentration of other elements. However, thanks to the well-established physical basis of XRF, calculations can explain measured XRF spectra to some extent. In modern practical analysis, the most likely difficulty to be encountered is in preparing so-called 'standard samples' that have the same matrix of the unknown sample to be analyzed. In such cases, one might wonder how one can depend on calculations, or which type of experimental data would help. Such problems are not new, but have yet to be fully resolved. They are also likely to assume even greater importance in the future. The book includes numerous stimulating applications in the area of micro area analysis with X-ray microbeams and ultra trace analysis using the total reflection condition (Chap. 7). The use of synchrotron radiation contributed to pushing those techniques to state-of-the art levels, and development of such techniques is still in progress. The book delves into XRF instrumentation and seems particularly strong in X-ray optics (Chap. 3). One can learn about the latest technological advances in great detail. Progress in this area correlates to the advent of new sources, like synchrotrons and micro-focus laboratory X-ray sources. Finally, in the last three pages, Chap. 8.2, there is a very useful list of sources and links, i.e., URLs, book names etc. In short, owing to its sheer practicality, every X-ray laboratory should have a copy of the handbook, or even two or three.