Awards cite research on nanolaminated coatings, how atoms move, microlasers
By Chris Burroughs
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SELF ASSEMBLY -- Jeff Brinker (1831) won a DOE Basic Energy Sciences materials award for his work on two related areas of research involving molecular self-assembly as a means to prepare mesoporous films and nanocomposites. (Photo by Randy Montoya)
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"Winning three of these awards in one year is a reflection of the outstanding work that goes on here at Sandia," says George Samara (1152), manager of Sandia's BES/MS program. "These awards continue Sandia's tradition of excellence in the BES Materials Sciences Program. With only about five percent of the BES/MS budget, Sandia has won 34 of 165 awards since the inception of these awards in 1981."
He adds that what makes the BES awards extra special is that peer labs serve as judges.
"Each lab gets entries from other labs and votes on which ones they think are best," he says. "Our peers hold our work in high regard."
Fifty thousand dollars to be used in the purchase of capital equipment accompanies each award.
Jeff Brinker's 1998 award for Outstanding Scientific Accomplishment in Metal and Ceramic Sciences is his fifth BES award. He also won in 1986, 1992, 1994, and 1995.
Sharing the award for the entry titled, "Evaporation-Induced Self-Assembly of Nanostructured Films and Particles," are Alan Sellinger, formerly of Sandia, Yunfeng Lu of UNM, and Bruce Dunn and Jeff Zink, both of UCLA, who worked with Jeff, the principal investigator, on the project.
The award was given based on two related areas of research involving molecular self-assembly as a means to prepare mesoporous films and nanocomposites.
Mesoporous films are coatings -- less than one micron thick-- that are extremely porous, but with a precise network of pores of a controlled size and spacing. The film can be used as a membrane to separate molecules of different dimensions. Or it can be used as a low dielectric constant material for microelectronics.
The coating is made by removing a substrate from a liquid bath in a simple, continuous dip-coating procedure and forms as water and alcohol evaporate. The resulting material consists of pores in specific cubic or hexagonal arrangements.
A similar coating process is used to create organic/inorganic nanocomposites, which are tough, strong optically transparent coatings suitable for applications such as automotive finishes and coatings for implements and optical lenses.
The nanocomposite coating mimics the construction of seashells, which Jeff calls the "holy grail" of functional materials design. For both the porous and nanocomposite coating process two-sided detergent molecules, composed of hydrophilic (water-loving) and hydophobic (water-hating) portions, spontaneously form spherical molecular assemblies called micelles. In water the micelles arrange themselves so that the water-loving part of the detergent is in contact with water, while the water-hating, hydrophobic part is shielded in the micellar interior. Using a rapid and continuous dip-coating procedure, the micelles can be used to spatially separate and organize inorganic and organic precursors into hundreds of alternating layers in a single step. A low-temperature heat treatment polymerizes the organic and inorganic layers and bonds their interfaces. The result is a transparent nanolaminated coating that mimics the layered calcium carbonate/biopolymer construction of seashells.
Jeff says that winning the BES award is "very satisfying."
"We got involved in this research about four years after the first breakthroughs in the field," he says. "To come in the middle and make such an impact in such a short period of time is quite an accomplishment."
Continued research in how atoms move on a surface won Gary Kellogg the BES award for Sustained Outstanding Research in Condensed Matter Physics. His entry was called "Quantitative Measurements and New Mechanisms of Atom and Cluster Diffusion on Surfaces."
In 1990, colleague Peter Feibelman (1114) predicted that atoms have two ways of moving on a surface. Not only do they "hop" from place to place on the surface without disturbing the atoms underneath -- a phenomenon of which scientists have long been aware -- they also trade places with surface atoms by one atom pushing another out from the layer of atoms below.
By mapping out the sites that an atom visits as it moves across the surface, Gary verified that the exchange process is preferred over conventional site-to-site hopping on certain metal surfaces. These efforts won Gary and Peter a BES award in 1991.
Over the past eight years Gary has continued research in the area, coming up with some startling results that are defining the "laws" that govern whether an atom prefers to hop or exchange.
His insights into the nature of atom motion result from his ability to watch single atoms and small clusters of atoms as they meander across the surface of a crystalline solid. He uses a field ion microscope, which was the first instrument to resolve individual atoms on a solid surface.
In addition to single atoms, Gary has made detailed investigations of the movement of small clusters on surfaces, finding that there is a direct correlation between the speed at which a cluster moves and the configuration of atoms within the cluster. Most recently he has been studying the effects of common gases, such as hydrogen and oxygen on single-atom surface diffusion. He discovered that hydrogen strongly influences the rate of atom migration.
"The mantra of modern materials design is the right atom in the right place," Gary says. "My research is providing the scientific foundations that will help materials engineers in this quest."
A team approach using a handheld biocavity laser -- a device that analyzes biological cells by inserting cells into the laser itself to become part of the laser generating process -- won Paul Gourley, Mary Crawford, Weng Chow, Mike Sinclair, and Anthony McDonald the BES award for Significant Implications for DOE Related Technologies in Condensed Matter Physics. Their project was titled "Semiconductor Materials Science Enables a Biological Microcavity Laser for Early Detection of Disease."
"We have developed a revolutionary method for analyzing biological cells," says Paul, who also won BES awards in 1985 and 1993. "It provides us in a few moments information about the size, shape, and characteristics of the cells and does not require the customary chemical staining procedure to make the cell structure visible."
Last year Sandia and the National Institutes of Health patented the biocavity laser, which employs a laser device called a VCSEL, a vertical-cavity surface-emitting laser. Instead of extracting a laser beam that passes through blood cells and then yields data, the researchers insert cells into the laser itself to become part of the laser beam generation process. The results are quantifiable. If no cell is cancerous or unhealthy, the device emits a standard light signal, but a cancerous cell gives a bright flash at different wavelengths.
Although the biocavity laser was developed under laboratory-directed research and development funding, the BES/MS program funded the materials science that made the developments possible.
While Paul oversaw the project and did experiments with cells, several other Sandians worked with him as a team. They included Weng, who provided calculations of the range of operation of the device; Mike, who measured temporal characteristics of light emitting materials; Mary, who helped understand ways of injecting current into semiconductor material; and Anthony, who did cell experiments.
Paul says that besides its obvious medical implications, the microcavity laser has broad implications as a new tool for basic research in chemistry to understand the chemistry of how solids and fluids interact. It may be used to improve materials synthesis and processing, solar energy conversion, petroleum refining, and pollution monitoring.
Last modified: December 07, 1998
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