Preface for the special collection commemorating the career of Pat Thiel

This Special Collection in the Journal of Vacuum Science and Technology A (JVST A) has been compiled to commemorate the career of Professor Patricia (Pat) Thiel as a scientific leader in the international surface science community. Pat passed away in September 2020 due to breast cancer. This Collection includes 26 articles from colleagues, collaborators, and former Thiel group members. The topics overlap Pat’s scientific interests and advances in areas that include chemisorption, reconstruction, and complex formation on metal surfaces; submonolayer nucleation and growth and kinetic roughening of epitaxial thin films; coarsening of surface nanostructures; intercalation; surface phenomena for intermetallics including quasicrystals; and atomic-scale friction. We wish to thank the authors for their contributions towards producing this impressive Special Collection.

After graduating in Chemistry from Macalaster College in St. Paul in 1975, and working for a year at Control Data Corp., Pat performed her graduate studies in the group of W. Henry Weinberg at Caltech obtaining a Ph.D. in 1981. She then did a postdoc as a Humboldt Fellow in the group of Gerhardt Ertl at the University of Munich. This was followed by a staff position at Sandia National Laboratories before joining the Department of Chemistry at Iowa State University (ISU) in 1983 as an Assistant Professor, also with an appointment at Ames Laboratory USDOE. Subsequently, Pat was promoted through the ranks at ISU becoming a Distinguished Professor in 2001. Pat also served in the role of Chemistry Department Chair at ISU from 1999–2002, Program Director of Materials Chemistry (1988–2003) and Chief Research Officer (2008–2009) at Ames Laboratory, and held an appointment in the ISU Department of Materials Science & Engineering. Pat supervised 43 Ph.D. students and postdocs of whose accomplishments she was proud, and whose continued friendship she valued.

Pat’s science was diverse and extraordinarily impactful. Starting with her Ph.D. and postdoc, she studied chemisorption on metals particularly of H₂O, H, CO, NO, O, and S. In 1987, she published with Ted Madey a classic review of H₂O on metals,¹ currently with >2700 cites. The classic studies on chemisorption of CO helped provide the underpinnings of a detailed picture of the kinetics of CO-oxidation on Pt surfaces subsequently developed by the Ertl group.² Early work at ISU on chemisorption of oxygen elucidated both equilibrium and novel non-equilibrium ordering, as well as surface reconstruction.^3,4 Studies in the last decade focused on chemisorption of sulfur on coinage metals providing a comprehensive assessment of diverse phenomena including ordering, reconstruction, and particularly metal-S complex formation, which can lead to enhanced surface transport and dynamics.^5,6

At ISU, Pat also initiated studies of epitaxial growth of metal-on-metal films utilizing video LEED in the 1980s. With the availability of STM in the 1990s, her focus shifted to the submonolayer regime characterizing not just nucleation and growth of 2D metal homoepitaxial islands, but also their post-deposition evolution. Her group made the remarkable discovery that large 2D Ag islands or clusters on Ag(100) with up to thousands of atoms exhibited significant diffusive mobility across the surface,⁷ and, furthermore, that the associated cluster diffusion and coalescence (or Smoluchowski Ripening) dominated coarsening (as opposed to the expected Ostwald ripening).⁸ Later studies of multilayer homoepitaxial growth for Ag/Ag(100) provided the most comprehensive characterization of the subtle kinetic roughening and mound coarsening often seen in fcc(100) systems, and provided for Ag/Ag(111) the most detailed characterization of the complicated “dendritic wedding cake” morphologies which develop in this system.⁹ 

Also in the 1990s, moving beyond metal epitaxy on conventional single-component metal substrates, Pat initiated a major new effort at Ames Laboratory to study the surface science of quasicrystals. She later arranged for a part-time appointment at ISU of Dan Shechtman who received the 2011 Nobel Prize in Chemistry for the discovery of quasicrystals.¹⁰ Her quasicrystal studies first demonstrated that the surfaces were bulk terminated.¹¹ She later characterized various properties of these surfaces (oxidation propensity, friction, etc.) with collaborators in the scientific community exploring quasicrystals and related surface phenomena, a community that she embraced and supported through conference organization and other activities. In addition, Pat initiated efforts to study the growth of thin metal films on quasicrystals, the goal of which was, in part, to see if the substrate template could impart a quasicrystalline structure to the supported film. In this respect, her group discovered the nucleation of five-fold “starfish” Al clusters at the onset of deposition of Al on a fivefold icosahedral AlCuFe surface.¹² Other work investigated “quantum size effects” (QSE) reflected in the formation of height-selected Bi and Ag films on AlCuFe and AlPdMn.¹³ Later studies of metal deposition utilized the simpler bimetallic alloy substrate, NiAl(110), but also found novel phenomena including QSE reflected in a bilayer growth mode for Ag/NiAl(110), and nanoscale 2D Kirkendall effects in the stoichiometric self-growth of NiAl.¹⁴ 

In the last several years, Pat also initiated studies of metal deposition on a graphite substrate. However, in addition to traditional studies of metal nanocluster formation on top of the surface,¹⁵ her group showed that it was possible to encapsulate or intercalate (and thus protect) such nanoclusters in an interlayer “gallery” under the top graphene layers of the substrate.¹⁶ These novel nanostructures were achieved for high-temperature deposition of several metals provided that the substrate was first ion-sputtered to create defect portals allowing the metal to access the underlying galleries.

Pat’s scientific accomplishments were recognized with several major awards including the 2014 Medard Welch Award of the American Vacuum Society (AVS) for seminal contributions to the understanding of quasicrystalline surfaces and thin film nucleation and growth, the 2010 Arthur Adamson Award from the American Chemical Society for Distinguished Service in the Advancement of Surface Chemistry, and the 2010 David Adler Lectureship Award in the field of Materials Physics from the American Physical Society. She was a Fellow of the AVS, APS, MRS, and AAAS, and was inducted into the American Academy of Arts and Sciences in 2019. Pat was also the proud recipient of multiple awards and honors from ISU for her classroom teaching in chemistry, and for other contributions. Beyond being the recipient of multiple awards, Pat was extremely generous in her commitment of time and effort to nominate many of her colleagues, and also her students, for awards and fellowships.

Pat regarded her primary professional home as the AVS, and enthusiastically served in many roles for the society. These included serving as the AVS Surface Science Division Chair (1993), as the AVS International Symposium Chair (1995), as AVS Trustee (1997–1999), as AVS International Committee Chair (2015–2016), and as AVS Director (1994–1995 and also in 2019–2020 up to the time of her passing).

Finally, we wish to thank AVS Publications Office staff members, Rachel Bayne and Lindsey Lucas, and the JVST Editor-in-Chief, Eray Aydil, for their efforts in preparing this Special Collection.