Drastic Improvement in Energy Resolution in EDS Analysis by Transmission Electron Microscope

Realizing Ultra-high Accurate Analysis of Nanostructures by Newly Developed Spectrometer

2009.09.25

National Institute for Materials Science
SII NanoTechnology Inc.
Kyushu University
Japan Aerospace Exploration Agency
JEOL Ltd.

The National Institute for Materials Science, in a joint research project with SII NanoTechnology Inc., Kyushu University, Japan Aerospace Exploration Agency, and JEOL Ltd., successfully developed an analytical equipment in which a microcalorimeter type X-ray detector is mounted in a transmission electron microscope (TEM), and succeeded in obtaining X-ray spectra with energy resolution one order higher than that in conventional energy dispersive X-ray spectroscopy (EDS).

Abstract

  1. The National Institute for Materials Science (President: Sukekatsu Ushioda; hereinafter, NIMS), in a joint research project with SII NanoTechnology Inc. (President & CEO: Susumu Kitano), Kyushu University (President: Setsuo Arikawa), Japan Aerospace Exploration Agency (President: Kenji Tachikawa; hereinafter, JAXA), and JEOL Ltd. (President: Gonemon Kurihara), successfully developed an analytical equipment in which a microcalorimeter type X-ray detector is mounted in a transmission electron microscope (TEM), and succeeded in obtaining X-ray spectra with energy resolution one order higher than that in conventional energy dispersive X-ray spectroscopy (EDS). As a future objective, the team aims at realizing high accuracy compositional analysis at the nanoscale.
  2. TEM with an analysis function enables analysis of extremely small microstructures with high spatial resolution. As a result, this technique has become a basic tool in a wide range of research fields. X-ray analysis has been widely used in compositional analysis in these applications, but because the energy resolution of conventional semiconductor detectors4) is low, at 130-140eV, it was not possible to separate nearby X-ray peaks. As the size of the structures and microstructures of materials and devices has become progressively smaller, improved accuracy in compositional analysis using TEM has been strongly demanded. Dramatic improvement of energy resolution had become a key challenge for realizing higher accuracy.
  3. In this research, high energy resolution of 7.8eV was achieved by applying a superconducting transition edge sensor, which is a type of X-ray detector based on a detection principle different from the conventional type, to a TEM. This made it possible to separate a large number of overlapping peaks, which had not been possible to separate in the past, enabling high accuracy compositional analysis, in which peaks are separated from virtually all elements. At the same time, the trace element detection capability was also greatly improved.
  4. This dramatic improvement in the accuracy of compositional analysis with the TEM, which is used as a basic technique in a wide range of research fields, including nanotechnology/materials and biotechnology, is expected to have an important ripple effect on progress in those fields.
  5. The results reported here were achieved in research on the Research Subject “Development of Microcalorimeter Type X-ray Detection System for TEM” (FY2006-2008; Research Representative: Toru Hara) in the MEXT Leading Project, “Development of elementary techniques for electron microscope in next generation” (Supervisor: Ryuichi Shimizu, Senior Researcher, International Institute for Advanced Studies (IIAS); MEXT: Ministry of Education, Culture, Sports, Science and Technology of Japan). These results will be announced in the Journal of Electron Microscopy in the near future, and will also be presented at the international conference FEMMS09 (The Twelfth Frontiers of Electron Microscope in Materials Science, http://www.femms2009.org/) being held in Sasebo City, Nagasaki Prefecture, Japan, beginning September 27.