February 7, 2005

NSF Major Grants Provide Powerful Electron Microscopes

Dr. Mark Weaver and Dr. Gregory Thompson work with a student on the new scanning electron microscope

Dr. Mark Weaver (center), associate professor of metallurgical and materials engineering, and Dr. Gregory Thompson (right), assistant professor of metallurgical and materials engineering, work with a student on the new SEM. This SEM can magnify features greater than 500,000 times with an ultimate resolution of less than five nanometers.

The new FEI Quanta 3D dual-beam focus ion beam milled UA's logo onto the head of a pin.

by Mary Wymer

UA has experienced tremendous growth in its analytical research capability of materials during the last two years. Meeting the challenges of nanotechnology has propelled the growth. In support of this growth, the University is installing two state-of-the-art electron microscopes, SEM and TEM, to better understand the chemical composition and structure of materials at the nanometer scale.

A nanometer is one-billionth the length of a meter. Similar to an optical microscope which uses light to resolve objects, these microscopes use electron waves to image materials.

The SEM can magnify features greater than 500,000 times with an ultimate resolution of less than five nanometers. The TEM microscope can image materials at a magnification of one-million times.

These microscopes will allow scientists and engineers to study a variety of different materials at the nanometer scale to better understand their properties. Since an electron has a wavelength much smaller than light, it is possible to see features near or at the atomic level. These research microscopes, purchased by grants won from the National Science Foundation's Major Research Instrumentation (MRI) award, will be used for interdisciplinary research in the Colleges of Engineering and Arts and Sciences and will advance the University's goal in becoming a top research and scientific teaching institution.

Dr. Mark Weaver, associate professor of metallurgical and materials engineering, received a $622,000 MRI award in 2003, to purchase a JEOL 7000F Field Emission Scanning Electron Microscope (SEM). This microscope is equipped with various detectors including a secondary and backscatter detector which collectively enhance its imaging capability of material surfaces. The JEOL SEM is capable of the chemical identification of different atoms in materials by collecting characteristic X-rays, termed Energy Dispersive Spectroscopy (EDS), from the surfaces of materials.

Additionally, the SEM is equipped to perform Orientation Imaging Microscopy, which allows researchers to quantitatively determine the crystallographic orientation of individual grains and the identity of specific grain boundaries. The OIM images from the grains can be coupled with the chemical identification of the EDS to give a complete structural and compositional analysis.

Finally, the SEM is equipped to do electron beam lithography. Lithography is the rendering of an image on a surface. Because of the small wavelength of an electron beam, e-beam lithographic patterns can be as small as a few tens of nanometers.

Last year, Dr. Greg Thompson, assistant professor of metallurgical and materials engineering, received a $1.2 million MRI award to purchase a 200keV Field Emission FEI Tecnai F20 Super-twin Transmission Electron Microscope (TEM). At this ultra-high magnification, scientists can "see" individual atoms. By imaging at the atomic level, researchers understand how to engineer materials to improve such properties as electrical conduction and mechanical strength.

"A tool of this caliber affords the university community a tremendous research opportunity," Thompson said. "The analytical capability of this microscope will further strengthen the university's research infrastructure. By characterizing the atomic structure and composition of materials, we have new opportunities to fundamentally move science and engineering forward."

This TEM is equipped with a unique imaging detector, called a High Annular Angle Dark Field (HAADF) detector, which allows atomic level contrast imaging between different atomic numbered materials. This helps users distinguish the image contrast between materials as a function of the type of atom. This HAADF detector also allows the TEM to do tomography imaging. Tomography is a three-dimensional imaging technique that generates multiple viewing perspectives. By characterizing the overall shape of materials, at the nanometer scale, researchers gain a better insight into the structure of materials.

Similar to the SEM, this TEM is equipped with EDS for chemical identification mapping of materials at a resolution of approximately one nanometer. Finally, the Tecnai TEM's computer interface saves all individual settings making it a versatile, user-friendly microscope for all researchers.

The College of Engineering has invested in new research capacity by purchasing a FEI Quanta 3D dual beam Focus Ion Beam (FIB) instrument. The FIB uses an electron beam to image or view materials while simultaneously using a gallium ion beam to cut and shape materials at the nanometer level. The ion beam is able to machine intricate shapes, which enables the FIB to make site-specific specimens from regions of interests which are then studied in the new electron microscopes.

The electron microscopes will be housed and maintained in the Central Analytical Facility (CAF). The addition of these instruments makes UA a premier characterization facility in the Southeast and in the nation. These tools provide the UA faculty the resources to competitively renew existing programs and win new grants and contracts by having the capability to perform atomic level structural and chemical analysis.

The investigators involved in the NSF MRI proposal for the SEM and the TEM include Dr. Viola Acoff, professor of metallurgical and materials engineering; Dr. Martin Baker, associate professor of chemistry; Dr. Tonya Klein, Reichhold-Shumaker Assistant Professor of chemical and biological engineering; Dr. Gary Mankey, associate professor of physics; Dr. David Nikles, professor of chemistry and materials science; Dr. Rainer Schad, assistant professor of physics and astronomy; Thompson and Weaver. Additionally, several faculty members from the Colleges of Arts and Sciences and Engineering were involved as senior investigators on both projects.

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