8-9th August, 2008 School of Materials Science & Nanotechnology,Jadavpur University
Cubic aluminum nitride prepared via VLS technique using gold chloride as a catalyst in a single step process
R. Thapa, B. Saha, N. S. Das and K. K. Chattopadhyay*
Thin Film and Nanoscience Laboratory,
Department of Physics, Jadavpur University
Kolkata 700032, India
Abstract:
Group III-nitride semiconductors are the most promising candidate materials for field emission and optoelectronic devices applications in the ultraviolet and visible regions. Among these materials AlN has a large band gap of 6.2 eV, very small electron affinity, high thermal conductivity at low temperature, excellent chemical stability and nontoxicity. Aluminum nitride can be found mainly in two-phases, which are stable hexagonal wrutzite AlN and metastable cubic AlN. Cubic AlN possesses superior properties than hexagonal AlN; for example, it is suitable for doping and electro-acoustic devices were fabricated using this material.
Nanocrystalline cubic AlN thin films were synthesized by vapor-liquid-solid route on Si and fused silica substrates at appropriate conditions. The formation of cubic AlN was confirmed by x-ray diffraction studies. We also observed that AuCl3 plays an important role as a catalyst in the synthesis of well crystalline cubic phase of AlN. Energy dispersive analysis of x-rays confirmed the presence of nearly stoichiometric aluminium and nitrogen in the films. Fourier transformed infrared spectra showed characteristics absorptions of different vibrational frequencies. The cubic AlN nanostructured films also showed good electron field emission properties. The turn on field was found to be 11.9 V/μm and the maximum current density was ~1 A/m2. Optical properties of the cubic AlN films deposited on the fused silica substrates were studied by measuring the transmittance versus wavelength. The films showed good transparency and the allowed indirect band gap, measured from the transmittance spectra, was 3.83 eV.
*Corresponding author: email: ranjit.phy@gmail.com
email: kalyan_chattopadhyay@yahoo.com
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