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March 7, 2020 at 11:05 am

Knavel Models Solid-State Dewetting of Barium Thin Films

Sierra Knavel, portrait

Sierra Knavel

Ohio University senior HTC mathematics major Sierra Knavel is the lead author on an article about “A mathematical model of solid-state dewetting of barium thin films on W(112)” in the journal Mathematical Modelling of Natural Phenomena.

Knavel has had several undergraduate research experiences, spending the summer of 2019 at the University of California-San Bernardino on an NSF Research Experience for Undergraduates and the summer of 2018  at Valparaiso Experience in Research by Undergraduate Mathematicians in Indiana.

While pursuing a mathematics degree in the Honors Tutorial College at OHIO, Knavel also has served as a learning community leader and as a peer mentor in the Office of Multicultural Student Access and Retention.

Knavel is headed to Georgia Tech to pursue a doctorate in mathematics. “My future goal is to teach and conduct research at the university level,” she says.

Physics doctoral student Michael Mroz uses a low-energy electron microscope to examine the physical properties of compounds that make up thermionic cathodes.

Physics doctoral student Michael Mroz uses a low-energy electron microscope to examine the physical properties of compounds that make up thermionic cathodes.

Co-authors from OHIO, who are also members of the Nanoscale & Quantum Phenomena Institute, include Dr. Tatiana Savin, Professor of Mathematics; Michael Mroz, a graduate student in Physics & Astronomy; Dr. Martin Kordesch, Professor of Physics & Astronomy. Additional authors were from Brookhaven National Laboratory.

Mroz defended his dissertation on March 6 and graduates in May.

Abstract: Solid state dewetting occurs when a thin solid film is heated. The temperature of dewetting depends on the thickness of the film; dewetting can be observed in the range of 1∕3 to 1∕2 of the bulk melting temperature. While remaining solid, the film behaves in a manner similar to liquids dewetting and agglomerating to forming islands or droplets. One of the possible mechanisms is the conversion of a metastable thin film geometry into a more stable form. Heating the metastable film gives the film atoms higher mobility, and the films retract, dewetting the surface. This atomic motion can be restricted due to surface anisotropy. We present in situ emission microscopy observations of barium thin films deposited onto W(112) by thermal evaporation. From the modeling viewpoint, the evolution of the film in this system could be divided in four stages: (i) the nucleation and growth of the thin film as a simply connected region; (ii) formation of droplets/islands/hillocks; (iii) nucleation of holes; (iv) evolution of the components of the disconnected film to their equilibrium state. We present a continuum model that is qualitatively consistent with the evolution of the film observed at the initial stage of the experiment and discuss the later stages of the evolution of surface structures.

 

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