Journal
CURRENT APPLIED PHYSICS
Volume 19, Issue 2, Pages 143-148Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.cap.2018.11.012
Keywords
Ultrananocrystalline diamond; Coaxial arc plasma deposition; Spectroscopic ellipsometry; Optical parameters; Electron spin resonance
Funding
- Advanced Low Carbon Technology Research and Development Program (ALCA) of the Japan Science and Technology Agency (JST)
- Japan Society for the Promotion of Science (JSPS KAKENHI) [JP15H04127, JP16K18238]
- [JP17F17380]
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Ultrananocrystalline diamond/hydrogenated amorphous carbon composite films were deposited in the ambient of hydrogen by coaxial arc plasma deposition. The film compositions and chemical bonding structures were investigated by X-ray diffraction, X-ray photoemission and hydrogen forward scattering spectroscopies. The sp(3)/(sp(2)+sp(3)) ratio and hydrogen content in the film were estimated to be 64% and 35 at.%, respectively. The optical parameters and the optical dispersion profile were determined by using a variable angle spectroscopic ellipsometer at 55 degrees, 65 degrees and 75 degrees angle of incidence in the photon energy range of 0.9-5 eV. Combinations of multiple Gaussian, and Tauc-Lorentz or Cody-Lorentz dispersion functions are used to reproduce the experimental data. Results of ellipsometry showed a refractive index of approximately 2.05 (at 2eV) and optical band gap of 1.63 eV. The imaginary part of dielectric function exhibited a peak at 3.8 eV, which has assigned to pi-pi* electron transitions. Furthermore, Electron spin resonance measurements implied the existence of dangling bonds, which might have a partial contribution to the optical absorption properties of the deposited films. A correlation between optical parameters and structural profile of the deposited films is discussed.
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