The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

Nguyen, Duc; Girolami, Gregory S.; Mallek, Justin; Cloud, Andrew N.; Abelson, John R.; Lyding, Joseph; Gruebele, Martin

doi:10.1063/1.4901132

Title: The energy landscape of glassy dynamics on the amorphous hafnium diboride surface

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Abstract

Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB{sub 2} glass surface, two-state hopping of 1–2 nm diameter cooperatively rearranging regions or “clusters” occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB{sub 2} has a very high bulk glass transition temperature T{sub g}, and we observe no three-state hopping or sequential two-state hopping previously seen on lower T{sub g} glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements,more »« less

Authors:

Nguyen, Duc; Girolami, Gregory S. ^[1]; Mallek, Justin ^[1]; Cloud, Andrew N.; Abelson, John R. ^[2]; Lyding, Joseph ^[3]; Gruebele, Martin ^[1]

Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

Publication Date:: Fri Nov 28 00:00:00 EST 2014

OSTI Identifier:: 22413247

Resource Type:: Journal Article

Journal Name:: Journal of Chemical Physics

Additional Journal Information:: Journal Volume: 141; Journal Issue: 20; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY OF STATES; ELECTRIC POTENTIAL; FREE ENERGY; GLASS; HAFNIUM; HAFNIUM BORIDES; MOLECULES; RELAXATION; RESOLUTION; SOLIDS; SPECTROSCOPY; SURFACES; TRANSITION TEMPERATURE; TUNNEL EFFECT; TUNNELING

Citation Formats


                    Nguyen, Duc, Girolami, Gregory S., Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Mallek, Justin, Cloud, Andrew N., Abelson, John R., Lyding, Joseph, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Gruebele, Martin, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface.  United States: N. p., 2014. 
        Web.  doi:10.1063/1.4901132.

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                    Nguyen, Duc, Girolami, Gregory S., Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Mallek, Justin, Cloud, Andrew N., Abelson, John R., Lyding, Joseph, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Gruebele, Martin, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, & Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. The energy landscape of glassy dynamics on the amorphous hafnium diboride surface.  United States.  https://doi.org/10.1063/1.4901132

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                    Nguyen, Duc, Girolami, Gregory S., Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Mallek, Justin, Cloud, Andrew N., Abelson, John R., Lyding, Joseph, Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, Gruebele, Martin, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801. 2014.  
        "The energy landscape of glassy dynamics on the amorphous hafnium diboride surface".  United States.  https://doi.org/10.1063/1.4901132.

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@article{osti_22413247,

  title        = {The energy landscape of glassy dynamics on the amorphous hafnium diboride surface},

  author       = {Nguyen, Duc and Girolami, Gregory S. and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 and Mallek, Justin and Cloud, Andrew N. and Abelson, John R. and Lyding, Joseph and Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 and Gruebele, Martin and Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801},

  abstractNote = {Direct visualization of the dynamics of structural glasses and amorphous solids on the sub-nanometer scale provides rich information unavailable from bulk or conventional single molecule techniques. We study the surface of hafnium diboride, a conductive ultrahigh temperature ceramic material that can be grown in amorphous films. Our scanning tunneling movies have a second-to-hour dynamic range and single-point current measurements extend that to the millisecond-to-minute time scale. On the a-HfB{sub 2} glass surface, two-state hopping of 1–2 nm diameter cooperatively rearranging regions or “clusters” occurs from sub-milliseconds to hours. We characterize individual clusters in detail through high-resolution (<0.5 nm) imaging, scanning tunneling spectroscopy and voltage modulation, ruling out individual atoms, diffusing adsorbates, or pinned charges as the origin of the observed two-state hopping. Smaller clusters are more likely to hop, larger ones are more likely to be immobile. HfB{sub 2} has a very high bulk glass transition temperature T{sub g}, and we observe no three-state hopping or sequential two-state hopping previously seen on lower T{sub g} glass surfaces. The electronic density of states of clusters does not change when they hop up or down, allowing us to calibrate an accurate relative z-axis scale. By directly measuring and histogramming single cluster vertical displacements, we can reconstruct the local free energy landscape of individual clusters, complete with activation barrier height, a reaction coordinate in nanometers, and the shape of the free energy landscape basins between which hopping occurs. The experimental images are consistent with the compact shape of α-relaxors predicted by random first order transition theory, whereas the rapid hopping rate, even taking less confined motion at the surface into account, is consistent with β-relaxations. We make a proposal of how “mixed” features can show up in surface dynamics of glasses.},

  doi          = {10.1063/1.4901132},

  url          = {https://www.osti.gov/biblio/22413247},
  journal      = {Journal of Chemical Physics},

  issn         = {0021-9606},

  number       = 20,

  volume       = 141,

  place        = {United States},

  year         = {Fri Nov 28 00:00:00 EST 2014},

  month        = {Fri Nov 28 00:00:00 EST 2014}

}

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