CBE & MSE Seminar: Surface Kinetics of the Initial Stages of Cu and Cu Alloy Oxidation

Abstract: The transient stages of oxidation ¾ from the nucleation of the metal oxide to the formation of the thermodynamically stable oxide ¾ represent a scientifically challenging and technologically important terra incognito. These issues can only be understood through detailed study of the relevant microscopic processes at the nanoscale in situ. We are studying the dynamics of the initial and transient oxidation stages of a metal and alloys with in situ methods, including ultrahigh vacuum (UHV) transmission electron microscopy (TEM). We have previously demonstrated that the formation of epitaxial Cu₂O islands during the transient oxidation of Cu(100), (110) and (111) films bear a striking resemblance to heteroepitaxy, where the initial stages of growth are dominated by oxygen surface diffusion, and strain impacts the evolution of the oxide morphologies. We are presently investigating the early stages of oxidation of Cu-Au and Cu-Ni as a function of oxygen partial pressures and temperatures. For Cu-Au oxidation, the oxidation mechanisms change where the Cu₂O reveals a dendritic growth. For Cu-Ni oxidation, the addition of Ni causes the formation Cu₂O and/or NiO where the oxide type(s) and the relative orientation with the film depend on the Ni concentration, oxygen partial pressure and temperature.

Bio: William Kepler Whiteford Professor Judith C Yang received her Ph.D. in physics from Cornell University in 1993. She then went to the Max-Planck-Institute of Metallforschung, Stuttgart, Germany as an international NSF postdoctoral fellow. In 1995, she returned to the U.S. as a postdoc and visiting lecturer at the Materials Research Laboratory, University of Illinois at Urbana-Champaign. In 1999, she joined the engineering faculty at University of Pittsburgh. She is the 2002 recipient of the NSF CAREER award, 2004 B.P. America Faculty fellowship and the 2005 Chancellor’s Distinguished Research Award. She is an American Physical Society fellow (2017) and Microscopy Society of America fellow (2018) as well as a guest professor at Xi’an Jiatong University. Yang's research areas include oxidation, heterogeneous catalysis, nanomaterials, gas-surface reactions and transmission electron microscopy, especially in situ.

Host: Xiaoqing Pan