| Autor: |
Hoffman, A., Heiman, A., Strunk, H. P., Christiansen, S. H. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; 3/1/2002, Vol. 91 Issue 5, p3336, 9p, 4 Black and White Photographs, 1 Chart, 5 Graphs |
| Abstrakt: |
Nano-crystalline carbon films possessing a prevailing diamond or a graphite character, depending solely on substrate temperature and deposition time, can be deposited from a methane-hydrogen mixture by the direct current glow discharge plasma chemical vapor deposition method. In this study we investigate the evolution of nano-crystalline carbon films deposited in the 800-950°C temperature range onto silicon substrates aiming to enlight the physicochemical processes leading to the formation of nano-diamond films. While at a deposition temperature of ∼880 °C the formation of a thin precursor graphitic film is followed by deposition of a film of diamond character, at higher and lower temperatures the films maintain their graphitic character. The morphology of the films and their growth rate vary with deposition temperature: slower growth rates and higher film roughness are obtained at lower temperatures suggesting the importance of kinetic effects during the growth process. For deposition times longer than ∼60 min, similar morphologies are obtained irrespectively of the deposition temperature. A preferred spatial alignment of the basal planes of the graphitic film at the interface with the silicon substrate was determined. The alignment was found to differ with deposition temperature: at 800 and 880°C the alignment occurs along the graphitic a axis perpendicular to the silicon substrate, while at 950 °C the c axis is aligned perpendicular to the silicon substrate. However, it was determined that for films a few hundred nm thick close to the evolving surface the films display a preferred alignment of the basal planes vertical to the surface, irrespectively of their orientation at the interface. The reason for this alignment is suggested to be associated with a stress relaxation mechanism in the graphitic films. It was determined that film growth is accompanied by the evolution of large local stresses which obtain a maximum value for the... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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