Thermal transport across interfaces with molecular layers

Wang, Wei

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https://hdl.handle.net/2142/45578 Copy

Description

Title

Thermal transport across interfaces with molecular layers

Author(s)

Wang, Wei

Issue Date

2013-08-22T16:48:25Z

Director of Research (if dissertation) or Advisor (if thesis)

Cahill, David G.

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Thermal transport
• interfaces with molecules
• ultrafast
• transient absorption
• temperature dependence
• self-assembled monolayer (SAM).

Abstract

This thesis presents the experimental study of thermal transport across molecular interfaces. Molecular interfaces are fabricated by assembling Au nanocrystals with controllable surface chemistry onto oxide substrates such as quartz and sapphire. A self-assembled monolayer (SAM) of silane molecules is also grown on sapphire to make the third variety of molecular interfaces. The technique of transient absorption (TA) is used to probe the evolution of Au temperature following abrupt heating by an optical pulse. I modeled the heat transfer from the Au nanocrystals into the molecular coating and then to the substrate and I obtained the values of interfacial thermal conductance of Au/cetyl trimethylammonium bromide/quartz and Au/16-mercapto trimethylammonium bromide/quartz in the temperature range of 40 < T < 300 K. The room temperature thermal conductance (G) values of these interfaces are both 150 ± 15 MW m-2K-1. Low temperature measurements are carried out in an optical cryostat and the temperature dependence of G(T) is found to have the same form as the temperature dependence of the heat capacity of Au. These results suggest the spectrum of vibrational modes that carry heat through the molecular interfaces is similar to the vibrational spectrum of Au; and that anharmonicity does not significantly contribute to the heat transport in this system.

Graduation Semester

2013-08

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http://hdl.handle.net/2142/45578

Copyright and License Information

Copyright 2013 Wei Wang

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