Scientists Produce Smooth Gold Surfaces With Many Potential Uses

June 04, 1996

COLUMBUS, Ohio -- Physicists at Ohio State University have found a way to make very smooth gold surfaces that have a variety of potential applications.

One application would be to make mirrors in X-ray telescopes.

Another possibility is to use the surfaces to support biological specimens so that their individual molecules can be studied. One way biologists study molecules is to place a sample on a substrate, similar to a microscope slide, and place it under a scanning tunneling microscope (STM). An STM probes a sample using an electrical current and is able to see details more than 1,000 times smaller than a regular light microscope.

"To get good results from an STM, scientists need an electrically conducting, smooth substrate made of a substance that will not react chemically with the material they are studying," said Greg Lafyatis, an associate professor of physics at Ohio State.

Lafyatis, working with Nathan Woodard, a graduate student in physics at Ohio State, developed a technique to produce an extremely smooth gold surface. They put a coating of gold on a piece of glass and then peeled the gold and glass apart. By using the underside of the gold layer, the scientists produced a surface that was more than 10 times smoother than what is currently used.

"Because of its inertness, gold is a popular substrate for scanning tunneling microscopy of biological and large-organic- molecular studies," he continued. "The technique we've found will produce easy-to-make substrates of superior quality for workers in this field."

Lafyatis and Woodard developed the technique while trying to produce a smooth surface for a study sponsored by the National Science Foundation. The project will measure the forces on atoms near metal surfaces. They first needed to create a smooth gold surface -- in this case gold -- because a bumpy surface would produce inaccurate results.

"Gold is the most chemically stable metallic element," Lafyatis said. "Because of this, workers in many disciplines have previously sought to make smooth gold surfaces and we expect our technique will find applications far beyond our own."

To make the smooth layer of gold, the researchers evaporated a small amount of gold over a piece of glass. They then glued a waver-shaped piece of silicon to the top of the gold layer. After the silicon hardened, Lafyatis and Woodard pry the silicon off the glass, with the gold layer stuck to it.

"Using this technique, scientists can create smooth gold surfaces much larger than could be made previously," Lafyatis said. This technique could be used to make reflective coatings for large X-ray mirrors.

"When we got into this, people in the field could only make large smooth gold surfaces of about 100 atoms wide," Lafyatis said. "Now, it's feasible that a smooth gold surface of almost any size could be produced."

The work was published in a recent issue of Journal of Vacuum Science and Technology A - Vacuum Surfaces and Films.

Ohio State University

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