Acquisition of a Field Emission Scanning Electron Microscope for Nano- to Microscale Imaging and Chemical Analysis in the College of Engineering, University of Delaware

University Of Delaware, Newark DE

Investigators

Abstract

A field emission scanning electron microscope (FESEM) is sought for the University of Delaware College of Engineering (COE) electron microscopy center to fill an immediate, widespread need for nanometer resolution scanning electron microscopy. FESEM has become an indispensable instrument in conducting micro- to nanomorphological material imaging and chemical imaging/analysis. Importantly, true nanoscale data is obtainable from of an immense array of materials, spanning "hard" inorganics, both electrically conductive and insulative, to "soft" polymeric and biologicals. In comparison to traditional thermionic SEM (currenlty, the only functioning SEM in the college of engineering (COE) EM facility), the FESEM provides far superior resolution (nanostructures as small as 1 nm in diameter while our traditional SEM resolution is in the range of ~100 of nm) and can be operated at voltages as low as 0.5kV (the traditional thermal source in-house SEM must operate at ~30kV to reach its ultimate resolution of ~0.1 mm). It is important to stress that this low accelerating voltage allows direct nanoscopic imaging and elemental analysis of all materials currently being studied in COE and across the university. On the current COE SEM instrument, a JEOL JXA-840, imaging and chemical analysis is limited to conductive inorganics and only feasible at relatively low resolution (>0.1 mm for secondary electron imaging and ~1.0 mm for x-ray analysis). Polymeric and other insulating materials must be coated by a thick (~10's of nm) layer of conductive metal for feasible imaging which, consequently, completely masks true surface structure and chemistry. Biological materials with some level of hydration are simply not possible at ambient conditions in the traditional SEM due to high vacuum conditions. The sought FESEM system is equipped with state-of-the-art energy dispersive x-ray spectroscopy and a cryogenic transfer and cold stage for imaging of in situ, hydrated (vitrified) biological materials. With the large emphasis on nanotechnology in the current research paradigm, and certainly here at UD, this new FESEM will fill a large materials characterization gap in the college of engineering's research capabilities. Consequently, it is estimated that over 18 faculty members and 30 to 40 graduate students will immediately benefit in their research from the acquisition of the FESEM. Educational training opportunities for graduate students and advanced undergraduates represent a clear benefit to the university as a whole. At present, our electron microscopy facility serves about 30 students and post doctors for predominantly TEM research purposes. In addition, over 25 students from engineering and other natural science majors on campus use the facility for their course work (the new TEM course MSEG/CHEG 832 and the TEM lab module in MSEG602, Structure of Materials lab offered through Materials Science and Engineering). Specifically, a new MSEG602 lab module will be developed by the PI for specific FESEM introduction and instruction to incoming college of engineering graduate students. The addition of an FESEM will provide a unique opportunity for students at various levels and from various backgrounds to work in an interdisciplinary, advanced laboratory setting that is the College of Engineering electron microscopy center. Since the summer of 2001, we have utilized our JEOL FasTEM system, contained in the FEG2010 TEM microscope, to enhance our undergraduate and graduate classroom teaching and training. The FasTEM is a system integrated with our field emission transmission electron microscope (FE-TEM) that is capable of telecommunication and remote operation through computer networks. In addition to remote demonstrations, elementary and middle school students frequently visit the lab for in-house demonstrations of electron microscopy. It is obvious that these in-house and outside demonstrations generate significant student curiosity and interest in science and technology. To better achieve our educational outreach goals (and attract top quality undergraduates to the university) it is our desire that we also can demonstrate the nanostructures of modern engineered materials with an FESEM. Experience tells us that the 3-dimentional morphological images of the FESEM appeal more to K-12 students than 2-dimensional TEM data which is more difficult to interpret. Furthermore, the UD college of engineering electron microscopy facility has been highlighted in the popular media through a visit by the Discovery Channel in the fall of 2001. Microscopic details of fracture surfaces from metal cables of the Hindenberg were observed indicating the nature of catastrophic tensile failure. This type of popular media outreach will also be further pursued in the future during which we can highlight the new experimental capabilities of the college of engineering electron microscopy facility.