Low density of defect states in hydrogenated amorphous carbon thin films grown by plasma-enhanced chemical vapor deposition

K. M. Krishna, H. Ebisu, K. Hagimoto, Y. Hayashi, T. Soga, T. Jimbo, M. Umeno

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The density of electronic defect states in most forms of amorphous carbon deposited at room temperature is found so far to be very high (1018-1022 spins cm-3). In this letter, we demonstrate that the radio-frequency plasma-enhanced chemical vapor deposited hydrogenated amorphous carbon (a-C:H) thin film exhibits the lowest spin density of the order of 1016 cm-3, investigated by using electron spin resonance (ESR) spectroscopy, a very promising reproducible result comparable with high-quality a-Si:H. In addition, the optical gap of a-C:H has been tailored between a wide range, 1.8-3.1 eV. The ESR spectra of all the films reveal a single Lorentzian line whose linewidth ΔHpp varies strongly with the optical gap. Also, there is a strong dependence of spin density on the optical gap, and we show that this dependency is a direct result of structural changes due to sp3/sp2 carbon bonding network.

Original languageEnglish
Pages (from-to)294-296
Number of pages3
JournalApplied Physics Letters
Issue number3
Publication statusPublished - Jan 15 2001
Externally publishedYes


ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)

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