Several methods were employed for growth of nanotubes at the Department of Microelectronics of Faculty of Electrical Engineering and Information Technology in Bratislava. A halogen lamp heated furnace with alcohol vapors was used firstly. Attempts to grow nanotubes were done also using a conventional Plasma Enhanced Hot Filament-Chemical Vapour Deposition chamber, (PE HF CVD)which was later modified by adding an additional electrode. We examined various conditions which contribute to the growth of resulting nanotubes. We observed, that the influence of the atmospheric pressure and composition in the chamber is not questionable and is rather strict.
We used a silicon wafer as a substrate in the HF-CVD vacuum chamber modified by adding an additional electrode. The wafer was covered with sputtered material- Titanium Nitride and Nickel similarly to [2]. Methane and Hydrogen mixture was used in all experiments.Generally, nanotubes grew in a relatively broad range of pressures from 600 to 1100 Pa. In addition, we observed that non-oriented nanotubes had grown in the lower pressure region ( 250 - 300 Pa ), too. The efforts resulted in obtaining samples with spots of oriented nanotube structures.
The value of temperature in the modified PE HF-CVD chamber was varied between 500 and 700 °C during the experiments. Results of our experiments indicate that it is possible to grow nanotubes on small areas, but a large-scale oriented uniform nanotube production is in our conditions still a challenge. The preparation of nanotubes under the conditions of experiments within HF CVD with accomodated modified electrode seem to be a way to repeatable growth of oriented nanotube structures for now.This work was supported by grants VEGA 1/2040/05, 1/3034/06, 1/3095/06 and 1/2105/05.
[1] Kromka, A., Veis, P., Bederka, S: In Proc.Of the "The Second Conference on Electrical Engineering and Information Technology for PhD Students", 9th September 1999, Bratislava, Slovak Republic, pp.135-138 (ISBN 80-227-1256-6).
[2] Jyh-Hua Ting, Tsung-Lung Li, Ying-Chi Hong: J.Vac. Sci. Technol. B24 (4), Jul/Aug 2006, pp. 1794 – 1798.
[3] Vinduska, P., Janik, J., et al.: In Book of Abstracts 50th IUVSTA Workshop, October 22-26, 2006, Dubrovnik, Croatia.
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