Volumetric heat capacity enhancement in thin films of amorphous fluorocarbon polymers

Hongxiang Tian, Marc G. Ghossoub, Oksen T. Baris, Jun Ma, Murli Tirumala, Sanjiv Sinha

Research output: Contribution to journalArticlepeer-review

Abstract

Plasma deposited amorphous fluorocarbon polymers find use in biopassivation, and as low-friction coatings, adhesion promoters, and interlayer dielectrics. Here, we exploit their ease of deposition into ultrathin layers (<50 nm thick) to explore their potential as thermal storage elements. We design and fabricate a microcalorimeter for measuring the heat capacity of thin fluorocarbons. Conventional thin film calorimetry assumes adiabatic conditions that lead to large errors as film thickness decreases. We propose a new data analysis procedure that incorporates a one-dimensional solution of the transient heat diffusion equation to account for conduction losses. The data for films with thicknesses in the range 12-27 nm reveal a lowering of the melting point and an increase in the volumetric heat capacity with decreasing thickness. We attribute this to change in the carbon to fluorine ratio in the films' composition. The volumetric heat capacity approximately doubles at room temperature as the film thickness decreases from 27 nm to 12 nm.

Original languageEnglish (US)
Article number081601
JournalJournal of Heat Transfer
Volume134
Issue number8
DOIs
StatePublished - Jun 29 2012

Keywords

  • fluorocarbon polymer
  • heat capacity
  • thin film differential scanning calorimetry

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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