TY - JOUR
T1 - Mechanism of enhanced wettability of nanocrystalline diamond films by plasma treatment
AU - Yang, J. H.C.
AU - Teii, K.
N1 - Funding Information:
This work was supported in part by a Grant-in-Aid for Scientific Research (C) from the Japan Society for the Promotion of Science . The authors would like to thank K. Kitazume for cooperation in the experiments. K.T. acknowledges funding from the Murata Science Foundation and the Iketani Science and Technology Foundation .
Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2012/8/31
Y1 - 2012/8/31
N2 - The mechanism of wetting behavior of nanocrystalline diamond films is examined in terms of surface free energy, morphology, and bonding characteristics. The films are prepared by microwave plasma-enhanced chemical vapor deposition using Ar-rich/N 2/CH 4 and Ar-rich/H 2/CH 4 mixtures, followed by microwave hydrogen and oxygen plasma exposures separately. Contact angle measurement with water, ethylene glycol, and formamide reveals that both the as-deposited and hydrogen plasma treated films are hydrophobic, while the oxygen plasma treated film is extremely hydrophilic such that the contact angle is reduced down to almost zero degree. Fourier transform infrared spectroscopy reveals that the hydrogen atoms are dominantly bonded to diamond and amorphous sp 3-bonded carbon, and they are removed by the oxygen plasma treatment. For the oxygen plasma treated film, the mean value of oxygen concentration for the top surface to bulk (∼ 1 μm) measured by energy-dispersive X-ray spectroscopy is ∼ 10 at.%, while that for the top several monolayers surface measured by X-ray photoelectron spectroscopy is much higher at ∼ 37 at.%, indicating a higher degree of oxidation toward the surface. The carbon bonding state in the oxidized layer is disordered by incorporation of a large amount of oxygen in form of polar CO bonds, which is accountable for a greater polar component of the apparent surface free energy and stronger dipole-dipole interactions.
AB - The mechanism of wetting behavior of nanocrystalline diamond films is examined in terms of surface free energy, morphology, and bonding characteristics. The films are prepared by microwave plasma-enhanced chemical vapor deposition using Ar-rich/N 2/CH 4 and Ar-rich/H 2/CH 4 mixtures, followed by microwave hydrogen and oxygen plasma exposures separately. Contact angle measurement with water, ethylene glycol, and formamide reveals that both the as-deposited and hydrogen plasma treated films are hydrophobic, while the oxygen plasma treated film is extremely hydrophilic such that the contact angle is reduced down to almost zero degree. Fourier transform infrared spectroscopy reveals that the hydrogen atoms are dominantly bonded to diamond and amorphous sp 3-bonded carbon, and they are removed by the oxygen plasma treatment. For the oxygen plasma treated film, the mean value of oxygen concentration for the top surface to bulk (∼ 1 μm) measured by energy-dispersive X-ray spectroscopy is ∼ 10 at.%, while that for the top several monolayers surface measured by X-ray photoelectron spectroscopy is much higher at ∼ 37 at.%, indicating a higher degree of oxidation toward the surface. The carbon bonding state in the oxidized layer is disordered by incorporation of a large amount of oxygen in form of polar CO bonds, which is accountable for a greater polar component of the apparent surface free energy and stronger dipole-dipole interactions.
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U2 - 10.1016/j.tsf.2012.06.041
DO - 10.1016/j.tsf.2012.06.041
M3 - Article
AN - SCOPUS:84864769834
VL - 520
SP - 6566
EP - 6570
JO - Thin Solid Films
JF - Thin Solid Films
SN - 0040-6090
IS - 21
ER -