Effect of Power Density on the Electrochemical Properties of Undoped Amorphous Carbon (a-C) Thin Films

Tommi Palomäki, Miguel A. Caro, Niklas Wester, Sami Sainio, Jarkko Etula, Leena Sisko Johansson, Jeon G. Han, Jari Koskinen, Tomi Laurila*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

4 Citations (Scopus)

Abstract

Undoped a-C thin films were deposited with varying power density from 10 to 25 W/cm2 using unbalanced closed-field magnetron sputtering (CFUBMS). The effect of power density on the physical and electrochemical properties was investigated by experimental characterization methods and atomistic simulations. XPS indicated that the films were composed mostly of sp2-bonded carbon (55–58 at.%) with a small amount of oxygen (8–9 at.%) in the surface region. The films appeared completely amorphous in XRD. The ID/IG ratio obtained by Raman spectroscopy indicated an increase from 1.76 to 2.34 with power density. The experimental and simulated data suggested a possible ordering and/or clustering of the sp2 phase with power density as the cause of the improved electrical properties of the a-C films. The electrochemical properties of a-C were between those of glassy carbon and tetrahedral amorphous carbon with potential windows ranging from 2.77 to 2.93 V and double-layer capacitance values around 0.90 μF cm−2. Electron transfer for Ru(NH3)6 3+/2+ and FcMeOH+1/0 was reversible whereas that for IrCl6 2−/3− was quasi-reversible. Peak potential separation of dopamine and oxidation potential of ascorbic acid decreased with power density, correlating with the structural and electrical changes of the films. The a-C thin films deposited by CFUBMS are inherently conductive and their physical properties can be adjusted by varying the deposition parameters to a wide range of electrochemical applications.

Original languageEnglish
Pages (from-to)746-755
Number of pages10
JournalELECTROANALYSIS
Volume31
Issue number4
Early online date1 Jan 2019
DOIs
Publication statusPublished - 1 Apr 2019
MoE publication typeA1 Journal article-refereed

Keywords

  • amorphous carbon
  • ascorbic acid
  • closed-field unbalanced magnetron sputtering
  • dopamine
  • electrochemical properties
  • CATALYSIS
  • HETEROGENEOUS ELECTRON-TRANSFER
  • PERFORMANCE
  • ELECTROANALYSIS
  • NITRIDE
  • BORON-DOPED DIAMOND
  • KINETICS
  • GROWTH
  • DOPAMINE
  • SURFACES

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