MRI: Development of a high energy-loss electron spectrometry system with improved detection sensitivity for an advanced electron microscope

Lehigh University, Bethlehem PA

Investigators

Abstract

Electron energy loss spectrometry (EELS) in the (scanning) transmission electron microscope has become an essential tool for materials characterization. EELS can provide insight on chemical composition and bonding, which is similar information to that generated by synchrotron X-ray methods available at several large facilities. In this research project, a new type of EELS system will be developed, which is more versatile and can detect more elements than currently achievable in existing systems. It will also have the advantage of greatly improved spatial resolution down to the nanoscale, which is considerably better than can be achieved at synchrotron sources. The new EELS system effectively transforms the (scanning) transmission electron microscope into the equivalent of a synchrotron facility but with improved spatial resolution. This instrumentation developed will impact a wide range of research activities across broad sectors of materials science ranging from semiconductors to advanced alloys. It will support projects not only internal to Lehigh, but also from other universities, government labs and industry. The knowledge developed will be presented to many Lehigh students via classes taught by the PI/co-PIs and also to numerous industry/government attendees of the Lehigh Microscopy Schools. A joint symposium will be organized between the synchrotron and electron microscopy communities to exchange knowledge on this fertile overlapping research area. The new EELS system has four major components: (1) an EELS spectrometer with improved optics design for the detection of higher energy-loss electrons, (2) an ultra-high sensitivity electron detector for lower signal detection in the high-energy-loss range, (3) a multi-functionality scan generator for flexible electron probe control and (4) an integrated software platform to efficiently control not only the spectrometer and detector, but also the microscope to record high-energy-loss signals while maintaining high spatial resolution and allowing energy-filtered imaging. The new high-energy-loss EELS system will be able to detect energy-loss signals up to ~13,000eV. This means that K ionization edges up to Se (Z = 34, including all 3d transition metals), L-edges up to Tl (Z = 82, including all the lanthanoid series) and M-edges up to U (Z = 92) can be recorded by the new EELS system. The palette of materials systems that become accessible for EELS analysis will be broadened to include for example, gold nanoparticles for various catalytic applications, high entropy alloys with heavy elements and rare-earth based light-emitted diodes. The software packages created through this development project will be made freely available for future users. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.