Basic Research Capability : ‘Scanning Tunneling’ Microscope Focuses on Atoms

A microscope built in a California garage by a Stanford University student is giving the University of Utah fundamental research capabilities that exist only in a handful of the world’s institutions.

The microscope, a “scanning tunneling microscope” that is based on the design of the original STM built in 1981 by scientists at IBM’s Zurich, Switzerland, research facility, allows scientists to “see” atoms for the first time.

The university received the 12th and last STM to be built by Doug Smith and his partner, Calvin F. Quate, a Stanford professor. Smith has joined IBM in Zurich as a researcher. The two IBM scientists who invented the STM in 1981 shared the 1986 Nobel Prize for physics.

The STM appears to be nothing more than six layers of stainless steel plates stacked vertically and separated by small rubber insulators. It looks more like something from a turn-of-the-century laboratory than one of the most important research discoveries of this century.

The $25,000 STM was bought by the university’s Center for Biopolymers at Interface, one of the state’s Centers of Excellence programs. The center is funded by state and private industry, and the microscope was bought by the university and the center’s 10 industrial members, said Karin Caldwell, the director.

The most remarkable thing about the STM is its simplicity and ease of operation, compared to large electron microscopes such as the transmission electron microscope or the scanning electron microscope. Both of these instruments require special rooms with controlled environments and complex preparation of samples to be viewed. The STM, on the other hand, can be operated nearly anywhere as long as it is supported by a stable surface, such as an optical table.

In order to understand how powerful the STM is, imagine looking at the entire universe from side to side, and then realize that the STM examines in great detail an area that, compared to the entire universe, would be only the size of Ogden, Utah.

“You’re looking at the atomic level of organization,” said Peter Gerity, assistant dean of the College of Engineering. “In 1970, we began to talk about the possibility of doing this some day. Forecasters envisioned this, but no one ever dreamed it would come this quickly.”

The microscope gets its name--scanning tunneling--from quantum physics, the “new” branch of physics that has been used to explain, since shortly after 1900, how the universe works. Tunneling is a phenomenon that involves the passage of electrons between two materials that are narrowly separated by a non-conducting area such as an insulator or vacuum.

In quantum mechanics, electrons behave like “clouds” that spill out slightly beyond the surfaces of the materials in which they originate. If two materials are brought so close that their electron clouds intermingle, and if a voltage is applied across them, a current--the movement of electrons--will occur between the two separated clouds. This tunneling phenomenon is the key to the operation of the STM.

A very sophisticated power supply, which accounts for about three-quarters of the STM’s cost, is necessary to operate the device.

Chen-Ze Hu, who received his doctorate in materials science from the university, operates the STM and, since its arrival last week, has compiled pictures of several surfaces at the atomic level.

Caldwell said the STM is a valuable tool in her center’s search for knowledge about how biopolymers such as proteins adhere to, or release from, other materials. “In some ways, we know more about the far side of the moon than we know about this subject.”

In order to make biologically compatible materials for human implantation, scientists need to know how the substances react with polymers such as proteins, she said. Questions the STM are expected to answer include whether the proteins clump together on the surface or spread out. “We also need to know whether they are the same species when they seat themselves on the surface as when they are in solution,” she said.

“Here, for the first time, we have the ability to actually monitor the contours of the molecule on the surface. We can immediately see if it is round in solution and then starts spreading when it seats itself on the surface. We can see how it changes and what face of the molecule is turning itself toward the outside world and what is turning itself inside.”

The STM will tell scientists how closely spaced the molecules are and whether they completely cover a surface or clump together, she said.

Another use of the STM will be in improving the quality control of solid-state devices, which currently have a high rate of defects because they can’t be monitored during all the steps of manufacturing. As computer chips evolve, their structural details are getting so small that it is vital to understand them at the atomic level, Caldwell said.