Contacts:
Vince Crist, Materials Preparation Center, (515) 294-4781
Robert Mills, Public Affairs, (515) 294-1113

New instrument provides more complete and accurate analysis of materials

AMES, Iowa — A new, one-of-a-kind Auger electron spectroscopy microscope at the U.S. Department of Energy’s Ames Laboratory gives researchers new insights into critical materials used in semiconductors, automobiles, catalysts, optics, thin films, computer hard disks and elsewhere.

The Auger (pronounced oh-zhay) microscope is an analytical device that allows scientists to understand the composition of surface layers as well as the distribution of elements in materials. Such capability is important to researchers evaluating material properties, failure, corrosion, surface cleanliness and other factors. The desk-sized system, which cost $850,000, is run by the Materials Preparation Center at the Ames Lab.

"The new Auger microscope is an enormous benefit to Ames Lab researchers and MPC’s outside clients," said Larry Jones, MPC director. "We have a unique capability to provide researchers with information they need to move their research ahead more rapidly."

Auger electron spectroscopy is not new. But the MPC machine, built by Japan Electron Optics Laboratory, has benefits over traditional Auger systems. "The big advantage of this type of system is that the probe is very small," said Vince Crist, an assistant scientist at Ames Lab and manager of the surface analysis lab in which the new instrument is housed. As a result, the system can resolve a region roughly 10 times smaller than older Auger devices. Resolution refers to the smallest distance between two points on a sample that can still be distinguished as two separate entities; higher resolution means the instrument can generate a more complete and accurate characterization of a material sample.

Crist, a chemist who joined Ames Lab in 1999, knows Auger technology well. For the past 13 years, he was a demonstration engineer, salesman and scientist for a manufacturer of Auger and similar machines in Japan. "Our Auger is the first of its kind in the world," said Crist.

Unlike older Auger machines, the MPC unit can directly analyze the chemical state of materials in a sample. So, for instance, it can quickly and accurately reveal the amount of silicon in a sample that exists as the element compared to the amount of silicon oxide. Such information can also be used to create a detailed map of elements and their chemical states across a sample.

Auger microscopes work by focusing an electron beam onto the surface of a material sample, producing special electrons (called Auger electrons) with energies unique to each element or chemical compound contained in the top layers of atoms. The instrument then analyzes the number of electrons as well as their kinetic energy, generating data and maps that help scientists understand surface qualities. Auger microscopes can also obtain information on the composition of materials below the surface, thanks to an ion gun that gradually "peels" material from the sample surface.

The surface analysis provided by Auger machines is of particular interest to scientists because the outer atomic layers are where a material interacts with its environment. For instance, processes such as oxidation, corrosion and wear start at the surface.

The new MPC machine is computer controlled. Analysis results can be exported in common data and image file formats. The system adds to MPC’s arsenal of advanced equipment for microstructural and microchemical materials characterization. Indeed, the MPC has a similar instrument — which uses a technique known as X-ray photoelectron spectroscopy — with complementary capabilities. "They are the dynamic duo of the surface science field," said Crist, speaking of Auger and XPS technologies.

Funding for the new machine came from the U.S. Department of Energy. The MPC is a DOE user facility. The center provides research and developmental quantities of high-purity materials and unique characterization services not available from the private sector to scientists at university, industry and government facilities on a cost-recovery basis.

Ames Laboratory is operated for the DOE by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.

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Last revision: 7/21/00 dbm

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