"I wouldn't say that MRL was particularly well known for inventing instruments so much as it was for getting our hands on the stuff as soon as possible and trying to figure out what you can do with it," says William B. White, professor emeritus of geochemistry, about the Materials Research Laboratory he was associated with for 40 years.
The Materials Research Laboratory, the predecessor of the Penn State Materials Research Institute, produced some of the most highly cited researchers in the field of materials. Among them is White, whose paper on the Raman spectrum of carbon, coauthored with Diane Knight in 1989, has been cited 1289 times to-date. White, who retired from Penn State in 2002, is known as much for his work on the geology of caves as for his materials research. He is the author or coauthor of more than 400 scientific papers and the author or editor of 7 books, including Encyclopedia of Caves (2005).
One of the pioneering areas of research at MRL was with an early version of the electron microprobe, which is now standard instrumentation in many labs. Originally conceived of as a tool for chemical analysis, the electron microprobe was brought to Penn State by Eugene White, an MRL colleague of Will White, who used the instrument to perform a series of experiments on crystal structure, taking it into new fields of research.
Another pioneer of instrumentation was K. Vedam, a professor of physics in MRL, who built some of the earliest ellipsometers, including the first ellipsometer capable of real-time observation. Ellipsometry is a powerful tool for nondestructive characterization that is widely used in the semiconductor industry to characterize thin films and more recently to study biological materials. It uses polarized light to probe the surface structure of materials with an accuracy down to the level of angstroms. As computers became available, the range of applications for ellipsometry expanded into new areas. Some of the recent developments in ellipsometry are the work of Susan Trolier-McKinstry, professor of materials science and director of the W.M. Keck Smart Materials Integration Laboratory, a part of the Materials Research Institute, who took over the ellipsometry from Vedam when he retired, says White.
"One of the things we should probably take credit for is the invention of the centralized facilities, the precursor of our Materials Characterization Lab," White suggests, thinking back to his graduate school days.
Called the Mineral Constitution Laboratory, it was the brainchild of E.F. Osborn, who was dean of the College of Earth and Mineral Sciences at Penn State at that time (the mid to late 1950s). Osborn recognized that researchers needed access to high priced instrumentation that might not be available. At the time, it was typical for researchers to barter for the use of another researcher's equipment, especially the x-ray diffraction tools needed by most earth scientists. Osborn created a central laboratory on the third floor of Hosler Building with an x-ray diffraction lab and a wet chemicals lab with a staff analytical chemist, and brought in an emission spectrograph and an infrared spectrometer. Having a central facility gave the researchers the chance to get new instruments as they came along.
Among these was the scanning electron microscope, one of the first obtained by any university. The SEM is a tool that has proved its worth over the years, White says. SEM uses a focused electron beam to scan small areas of solid samples. By collecting secondary electrons emitted from the sample, a magnified map of the surface can be built up. Today, the Materials Characterization Lab operates five SEMs, including a field emission scanning electron microscope and an environmental SEM.
Raman spectroscopy was another technique that found its way into the centralized facility, now largely consolidated in the newly built Materials Research Laboratory Building. White was deeply involved in early work on the new instrument. People were just beginning to develop commercial instruments. Rustum (Rustum Roy, first director of MRL), who always had his radar out for that kind of thing, was visiting with one of the principal scientists at Southern Cal who had developed these while at Bell Labs.
Rustum came back and said "We've got to have one of these," as Rustum was wont to do. We had some equipment money left in the kitty from building the new building, and we put it into one of the first Raman spectrometers to come on the market.
"We can probably take credit for applying Raman spectroscopy to mineralogy and materials, learning how to interpret the spectra of solids and the spectra of glasses, which people hadn't really done much with," White says. "That's a common theme. Not that we invented the gadgetry, but that we could see early on materials applications for the gadgetry."
Raman spectroscopy is a nondestructive technique that relies on the inelastic scattering of light by the vibration of the sample's molecules. In the early days, White says, it was a tedious process to gather data, requiring photographic plates to capture the emitted photons. The invention of the laser gave the researchers a powerful new light source, replacing the mercury arc. Today, the MCL maintains a confocal Raman spectroscope for surface and thin film characterization.
The first microscope capable of atomic resolution was built in a lab on the second floor of Osmond Hall, the home of Penn State's Department of Physics. Erwin Mueller, who had invented field emission microscopy (FEM) in the 1930s in Germany, came to Penn State in 1951 and led the team that developed the field ion microscope, which on October 11, 1955, showed "the first atomically resolved images of a solid atomic lattice." (Melmed, 1996)
Mueller, who studied physics under Gustav Hertz, was another of the founding faculty of MRL. White says, "A lot of people were of the opinion that he (Mueller) should have gotten the Nobel Prize for that invention. He didn't and he's gone now."
According to White, Mueller found that if you take an extremely sharp point, and in a vacuum chamber, put a very high voltage on that point, the corona discharge of electrons would strip atoms off the point and send them in a straight line to some sort of detectors. This would reveal an array of dark spots that gave a picture of individual atoms. "It was essentially a precursor of the scanning tunneling and atomic force microscopes."
Later, Mueller and his students Douglas Barofsky and J.A. Panitz went on to develop the Atom-Probe Field Ion Microscope, which combined FIM with a timeof- flight mass spectrometer to detect and analyze a single atom on a metal surface. Another of Mueller's students, Russell D. Young, went on to the National Bureau of Standards (now NIST) where he invented the topografiner in 1971, the first successful scanning probe microscope.
In the 1950s, high pressure materials research was pioneered within Penn State by Frank Tuttle from the geochemistry department. Tuttle's research produced a series of important papers in this early modern age of hydrothermal research. Rustum Roy, then a young faculty member, modified a design for a hydrothermal vessel that Tuttle had created but never developed. Both simple and highly versatile, this "test-tube bomb" became the standard laboratory device for hydrothermal research throughout the world for the next decade.
A series of 8" cylinders could be lined up with a single pressure source, and used for crystal growth, materials synthesis, the study of phase equilibria, and other basic and applied materials research. For several decades, MRL was one of the world's leading labs for high pressure, high temperature research, transitioning their results to the chemical industry, and, in the seventies, into nuclear waste packaging.
"It's a powerful way of doing chemical reactions," says White. "You mix up stuff with a solvent, weld it into a gold tube and put that inside a turbine steel vessel about 1" to 1 Â in diameter. You can pump water into it at a pressure of 50,000 - 60,000 pounds per square inch, then put it in a furnace and heat it up to 600 degrees C or so. The water in there tends to make the chemical react pretty vigorously.
Another approach to high pressure research adapted in the MRL was originally invented at Harvard by Nobel Prize-winning physicist Percy W. Bridgman. The MRL adaptation of the Bridgman anvil device involved grinding a quarter-inch flat face from the conical top of a specially hardened steel piston. "Pressure is force divided by area, so the pressure applied to the quarter-inch faces could reach values of 80,000 to 90,000 atmospheres," White remarks.
One piston was mounted against a steel frame and the other rested on a hydraulic jack. "The ones we built were basic junkyard construction," recalls White. They used 20-ton truck jacks, the kind available at any auto parts store, and pumped oil into their base at 5,000 psi. The sample went in between the two piston bases, often as a powder, and the pistons could be heated up to 400 to 500 degrees C. In one important experiment, they took a zinc oxide powder and under pressures up to 100,000 atmospheres, changed its structure into a new form, that of sodium chloride - rock salt.
The jacks were cheap enough that they could set up a row of them along a lab bench. When they broke, which happened often, it sounded like a canon going off in the lab, White recalls. Later, a researcher at NIST developed a different device based on the same principle, the diamond anvil cell, which along with the development of the laser made it possible to reach higher pressures and at the same time measure spectra or X-ray patterns by directing laser or X-ray beams through the transparent diamond. The realm of possibilities increased tremendously. The diamond anvil cell is now the work horse for research at extreme pressures.
The search to create synthetic diamond stretched back into the early 19th century, but after the Second World War, successes with high pressure research began to pay off in the form of new phases of materials, such as silica. Companies around the world were racing to be the first to achieve synthetic diamond, and in 1955, General Electric announced they had succeeded, using a modified version of the Bridgman device.
GE's diamond program was closely tied to Penn State, with a string of former graduate students becoming successive heads of GE diamond production. For the next several decades, much of the scientific work on high pressure synthetic diamond was centered at Penn State and MRL.
In the 1980s, Rustum Roy was traveling frequently to Russia to collaborate on high pressure diamond production. At about that time there were scientists in Russia claiming they could make diamond at atmospheric pressure, a claim that was met with general derision, according to Roy. When he visited their lab, he found that, despite using crude apparatus, they seemed to be succeeding at creating diamond out of gas at one atmosphere. Roy decided he would try to duplicate the feat at MRL.
Roy picks up the story. "I came home and got together with Tarasanker DebRoy, who knew about lasers. We set up a 500 watt laser and began making diamond in open air. Nobody believed that was possible." Roy picks up the story. "I came home and got together with Tarasanker DebRoy, who knew about lasers. We set up a 500 watt laser and began making diamond in open air. Nobody believed that was possible."
The result was a thin film of what was arguably diamond, although it was not easy to tell with typical x-ray diffraction methods. It was here that the pioneering work on Raman spectroscopy at Penn State paid off. It turned out that the Raman spectrum of diamond is unique. When Will White bounced a laser beam off of the thin film, it produced a single sharp line at a frequency that indicated diamond. "A lot of companies thought this was pretty exciting stuff," White recalls. Around thirty companies joined Penn State to form a diamond consortium, and chemical vapor deposition of diamond films took off worldwide.
Along with the evolution of the early Mineral Constitution Laboratory into today's Materials Characterization Lab, came the beginning of one credit short courses to teach students how to use instruments and interpret data. Prior to this innovation, students might go into the lab and be shown how to use the equipment, but without knowing much about what it was they were measuring. Short courses within the Department of Materials Science and Engineering taught students about the physics going on inside the instruments and how to interpret the data with more understanding.
With the emergence of MRI's user facilities, the Materials Characterization Lab offers short courses at Penn State aimed at educating students, faculty, post docs, staff, visitors, and industry in various materials characterization techniques. Recent short course offerings included Scanning Electron Microscopy (SEM), Particle Characterization, and Powder X-ray Diffraction (XRD).
Aside from a worldwide reputation as an expert on karst and cave hydrology, White has been involved in many of the innovations in materials at Penn State over the past four decades, publishing on a wide variety of topics. Most important of these are his work in infrared and Raman spectroscopy, learning how to use those techniques for the theoretical interpretations of the spectra of solids and applying that knowledge to specific materials, including glass, crystal, and the spectra of minerals.
The highly cited paper from 1989 mentioned above was an attempt to make up for the lack of any real defining reference work on the spectra of carbons. He and Diane Knight ran Raman spectra on every form of carbon they could find, from high quality diamond to crystal graphite to a burnt match. The resulting paper, published in the Journal of Materials Research, was used by nearly everyone involved in diamond films and the making of diamonds for the next two decades.
MRL'ss legacy of taking the latest instrumentation and learning how to use it in new ways is a tradition that continues at Penn State, as the accompanying articles in this issue illustrate. The Materials Research Institute is grateful to Prof. White for his pioneering contributions to the study of materials at Penn State.
William B. White is professor emeritus of geochemistry. Rustum Roy is Evan Pugh professor of the solid state emeritus.
This article was featured in Focus on Materials - Winter 2010.