Publication Type:

Journal Article

Source:

Journal of applied physics, New York, NY: American Institute of Physics, c1937-, Volume 94, Number 8, p.5252–5260 (2003)

URL:

http://homepages.rpi.edu/~duttap/Publications/2003JAP94.pdf

Abstract:

Nanocrystalline silicon carbide ~SiC! thin films were deposited by plasma enhanced chemical vapor
deposition technique at different deposition temperatures (Td) ranging from 80 to 575 °C and
different gas flow ratios ~GFRs!. While diethylsilane was used as the source for the preparation of
SiC films, hydrogen, argon and helium were used as dilution gases in different concentrations. The
effects of Td , GFR and dilution gases on the structural and optical properties of these films were
investigated using high resolution transmission electron microscope ~HRTEM!, micro-Raman,
Fourier transform infrared ~FTIR! and ultraviolet-visible optical absorption techniques. Detailed
analysis of the FTIR spectra indicates the onset of formation of SiC nanocrystals embedded in the
amorphous matrix of the films deposited at a temperature of 300 °C. The degree of crystallization
increases with increasing Td and the crystalline fraction (f c) is 65%62.2% at 575 °C. The f c is the
highest for the films deposited with hydrogen dilution in comparison with the films deposited with
argon and helium at the same Td . The Raman spectra also confirm the occurrence of crystallization
in these films. The HRTEM measurements confirm the existence of nanocrystallites in the
amorphous matrix with a wide variation in the crystallite size from 2 to 10 nm. These results are in
reasonable agreement with the FTIR and the micro-Raman analysis. The variation of refractive
index ~n! with Td is found to be quite consistent with the structural evolution of these films. The
films deposited with high dilution of H2 have large band gap (Eg) and these values vary from 2.6
to 4.47 eV as Td is increased from 80 to 575 °C. The size dependent shift in the Eg value has also
been investigated using effective mass approximation. Thus, the observed large band gap is
attributed to the presence of nanocrystallites in the films.

Cite this Research Publication

Dr. T. Rajagopalan, Wang, X., Lahlouh, B., Ramkumar, C., Dutta, P., and Gangopadhyay, S., “Low temperature deposition of nanocrystalline silicon carbide films by plasma enhanced chemical vapor deposition and their structural and optical characterization”, Journal of applied physics, vol. 94, pp. 5252–5260, 2003.

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