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Formation of Pentagonal Dimples in Icosahedral Diamond Crystals Grown by Hot Filament Chemical Vapor Deposition: Approach by Non-Classical Crystallization

1
School of Materials Science and Engineering, Pusan National University, Busan 46241, Korea
2
School of Convergence Science, Pusan National University, Busan 46241, Korea
3
Department of Materials Science and Engineering, College of Engineering, Seoul National University, Seoul 08826, Korea
4
Global Frontier R&D Center for Hybrid Interface Materials, Pusan National University, Busan 46241, Korea
*
Authors to whom correspondence should be addressed.
Coatings 2019, 9(4), 269; https://doi.org/10.3390/coatings9040269
Received: 21 March 2019 / Revised: 17 April 2019 / Accepted: 18 April 2019 / Published: 20 April 2019
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Abstract

In this study, acetone was used as a carbon source to deposit diamond films using tantalum filaments by hot filament chemical vapor deposition (HFCVD). For acetone fluxes of 80, 90, 130 and 170 standard cubic centimeters per min (sccm) and the respective hydrogen fluxes of 420, 410, 370, and 330 sccm, film thickness appeared to increase with increasing acetone, and high quality diamonds were deposited with well-defined facets of (111) and (100). For acetone fluxes of 210 and 250 sccm and the respective hydrogen fluxes of 290 and 250 sccm, however, the diamond quality was degraded with cauliflower-shaped structures evolving and the film thickness decreased with increasing acetone. The degradation of diamond quality was confirmed by Raman spectra and X-ray diffraction (XRD). Many diamond crystals grown at acetone fluxes of 80, 90, 130 and 170 sccm consisted of five (111) facets, indicating an icosahedral structure. At the corner where the five (111) facets met, there were pentagonal dimples, which implied that diamond crystals must have been etched. The decrease in film thickness at high acetone fluxes of 210 and 250 sccm also implied that the deposited film must have been etched. These results indicate that the two irreversible processes of deposition and etching occur simultaneously, which would violate the second law of thermodynamics from the classical concept of crystal growth by an individual atom. These puzzling results could be successfully explained by non-classical crystallization, where the building blocks for diamond films are nanoparticles formed in the gas phase. View Full-Text
Keywords: diamond; non-classical crystallization; icosahedral diamond; HFCVD; etching diamond; non-classical crystallization; icosahedral diamond; HFCVD; etching
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Song, C.W.; Jin, R.; Yang, J.-W.; Hwang, N.-M.; Kim, K.H. Formation of Pentagonal Dimples in Icosahedral Diamond Crystals Grown by Hot Filament Chemical Vapor Deposition: Approach by Non-Classical Crystallization. Coatings 2019, 9, 269.

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