Maurice Barnett “Barney” Webb

On 15 January 2021, the Surface Science community lost one of its architects and master practitioners, Maurice Barnett “Barney” Webb, who passed away at the age of 94 years. An unapologetic proponent of curiosity driven science he would often in conversations about research ask students past and present: “So, are you having fun?”

Barney was born on 14 May 1926 in Neenah, Wisconsin. He served in the Navy during World War II and then got his BS and PhD in physics from the University of Wisconsin-Madison; the PhD work was with William Beeman on small angle x-ray scattering from cold-worked metals. After graduate school he immediately joined the General Electric Research Labs, then one of the premier industrial R&D institutions, where he studied various aspects of metal thin films, including whisker formation, transport properties, and cyclotron resonances.

In 1961 the UW-Madison enticed Barney to return as a tenured associate professor. He recounted that while at General Electric he had heard a lecture by Lester Germer on electron diffraction as a test of quantum mechanics, and that lecture inspired him to begin his seminal work on low-energy electron diffraction (LEED) as a probe of atom arrangements at surfaces. A complication in LEED is the strong dependence of diffracted intensities on multiple scattering. Following a suggestion from surface scientist Wyn Roberts, Barney devised an approach that averaged the intensities over incident direction at constant momentum transfer and properly accounted for refraction to allow a quasi-kinematic description. That technique simplified the deduction of atom arrangements, including on nickel and silicon surfaces, and contributed to the eventual solution of the geometry of the Si(111) 7×7 reconstruction by Kunio Takayanagi.

Barney and his group also studied the effect of temperature in LEED, properly describing the dependence of the scattered intensity on phonon momentum based on an integration over a two-dimensional Brillouin zone. His group’s work also included investigations of temperature-driven order–disorder transitions on Si(111) and germanium (111) surfaces. A hallmark of Barney’s group was clever design of experiments using homebuilt equipment, which allowed them to keep pace with colleagues in industrial labs such as Bell Labs and IBM, with whom he interacted extensively.

Barney and his students used cryogenic physisorption of noble gases on metal surfaces to measure pressure-vs-temperature isosteres to probe atom interactions in quasi-2D systems and work out the properties of non-ideal 2D gases. They later extended that technique to test competing models for semiconductor reconstructions. In a particularly insightful set of experiments, he and his students directly tested the role of strain on step-reconstruction interactions by applying mechanical stress to cantilevered single crystal wafers and observing the results via LEED and scanning tunneling microscopy. In the process, they identified the dependence of step stiffness on the orientation of the steps relative to the reconstruction of atoms on the terraces. In 1987 the American Physical Society recognized his work on “the development of low-energy electron diffraction as a quantitative probe of the crystallography defect structure, and dynamics of surfaces” with the Davisson-Germer Prize—a particularly fitting tribute.

Despite his work on surfaces, he was far from two dimensional: An avid sailor, golfer, ping-pong player, cook, and woodworker, he delighted in using his physical insights in each of those activities. Although he had a very lively wit along with an ability to converse on a myriad of topics, his approach in interactions with others was always reasonable. Indeed he had a charming, self-effacing way about him, often starting a scientific conversation with “I don’t know much about this,” but then proceeding to demonstrate deep understanding about the issue.

He never missed a physics colloquium at the UW-Madison, regardless of the topic, and inevitably asked basic, thought-provoking questions that surprised many a speaker with his breadth of knowledge. He stated on multiple occasions that he was proud that nearly all of his students stayed in research; during his 85th birthday celebration he remarked that the most gratifying aspect of his career had been interacting with his students. He was generous with his time and was a talented, committed mentor. More than 20 years after his nominal retirement, he still came to the UW-Madison daily for lunchtime conversations with younger colleagues. Although he will be sorely missed, Barney’s legacy will continue through the insights and approaches he taught us that we now pass on to our own students.

Written by Ray Phaneuf, Max Lagally, Peter Bennett, Phil Cohen, Ed Conrad, Bob Joynt, F-K Men, Jim McKinney, Elizabeth Moog, James Schilling, Brian Swarzentruber, Bill Unertl, and John Unguris