Scanning Electron Microscope and Ion Beam Milling System for Nanoscale Analysis of Next-Generation Thermionic Cathodes and Novel Nanostructured Materials

The University of Kentucky (UK) requests support from the Department of Defense (DoD) to acquire a scanning electron microscope (SEM) with specialized analytical components for characterizing a range of materials using state-of-the-art techniques that will enable next generation technology in support of DoD missions. The proposed SEM will also serve the research community interested in materials characterization, and this additional utilization will enable cost recovery to support and sustain the new SEM. The existing electron microscopes in the Electron Microscopy Center (EMC) at UK offer excellent capabilities for general materials characterization, but do not allow the analysis of elemental/compositional aspects of specimens with the nanoscale resolution that is needed to characterize many modern materials. We propose to acquire a new SEM to establish state-of-the art nanoscale imaging and analysis capabilities at UK, serving key needs for multiple current DoD-funded projects as well as pending projects. Two current projects on dispenser cathodes, which lie within the realm of Electronic Warfare technology, will immediately benefit from the proposed instrument: “Reliable Manufacturing of Scandia-Doped Tungsten Powders for Thermionic Cathodes” (Phase 2)”, funded by the Navy STTR program; and “Escaping the Refractory Limit: Enabling New VED Operational Paradigms Through Mechanism-Based Re-Engineering of Thermionic Cathode Emitting Materials”, funded by the Defense Advanced Research Projects Agency (DARPA). Additionally, the SEM would impact multiple projects currently underway at UK, led by co-PIs Dr. Chad Risko (Department of Chemistry) and Mr. John Craddock (Center for Applied Energy Research). Moreover, Dr. Howard Roberts (Division of Restorative Dentistry) is developing projects of interest to AFOSR, which would also benefit from this equipment. The proposed instrument is a high-resolution SEM, with analytical capabilities geared toward surface measurements and also capable of extremely high spatial resolution. Recent developments in the analysis of low-energy x-rays (typically below 1 keV) emitted from the near-surface region of a sample facilitate characterization with low beam voltages in the SEM; in turn, the low beam voltage creates a shallow penetration depth (also down to ~10 nm), which enables a scanning nanoprobe mode for surface analytical measurements, i.e. combined imaging and elemental analysis with nanoscale spatial resolution. Additionally, an electron backscatter detector (EBSD) is included in the proposed configuration, for the nanoscale measurement of crystal structure/orientation. This combination of imaging and analytical capabilities will establish a unique system for the thorough characterization of nanoscale phases in near-surface sample regions. The proposed SEM would enable transformative research and significantly advance understanding of dispenser cathodes as well as other DoD-relevant materials. There remain a number of unanswered questions regarding nanoscale material phase and composition in these materials, and answering these key questions will be greatly facilitated by the state-of-the-art, unique SEM with nanoscale analytical capabilities, as proposed here.