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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/26345

Title: High pressure Raman spectroscopic studies on ultrananocrystalline diamond thin films: Anharmonicity and thermal properties of the grain boundary
Authors: Mishra, K. K.
Rani, Revati
Kumar, N.
Ravindran, T. R.
Kamatchi Jothiramalingam, Sankaran
Lin, I-Nan
Issue Date: 2017
Abstract: Ultrananocrystalline diamond (UNCD) thin film has been attracted widely to scientific community due to its attractive thermal and mechanical properties. Herein, we report the high-pressure behavior of grain boundary (GB) originated phonon modes and their correlation with thermal properties in UNCD film grown by microwave plasma enhanced chemical vapor deposition method. Spherical ultranano grains with size 3-4 nm in these films were investigated by high-resolution transmission electron microscopy (HRTEM). Raman spectroscopic studies of UNCD with a pressure transmitting medium (up to 16 GPa) and uniaxial pressure (up to 28 GPa) revealed the presence of grain boundary phonons which are found to harden upon compression. GB phonons contribution to the specific heat of UNCD at room temperature is estimated to be 4.7314 J/mol-K, which is similar to 80% of the reported theoretical molar specific heat C-v value (5.568 J/mol-K). Using our experimentally obtained mode Grtineisen parameters, GB contribution to the thermal expansion coefficient of UNCD is estimated to be 0.5 x 10(-6) K-1. Grain boundaries of UNCD are found to be highly stable and Raman spectra showed reversible behavior upon release of pressure. Phonon spectra as a function of temperature down to 90 K were used to obtain the anharmonicity of GB phonon modes. The first order temperature coefficient of trans-polyacetylene modes (v(1), v(2) and v(3)) and E-2g in-plane (G-band) modes of GB are obtained as -0.38 x 10(-2), 1.69 x 10(-2), -1.55 x 10(-2) and -1.41 x 10(-2) cm(-1) K-1, respectively.
Notes: [Mishra, K. K.; Rani, Revati; Kumar, N.; Ravindran, T. R.] HBNI, Indira Gandhi Ctr Atom Res, Mat Sci Grp, Kalpakkam 603102, Tamil Nadu, India. [Sankaran, K. J.] Hasselt Univ, Inst Mat Res IMO, B-3590 Diepenbeek, Belgium. [Sankaran, K. J.] IMEC Vzw, IMOMEC, B-3590 Diepenbeek, Belgium. [Lin, I-Nan] Tamkang Univ, Dept Phys, Tamsui, Taiwan.
URI: http://hdl.handle.net/1942/26345
DOI: 10.1016/j.diamond.2017.10.003
ISI #: 000418976200007
ISSN: 0925-9635
Category: A1
Type: Journal Contribution
Appears in Collections: Research publications

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