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Structural, Mechanical and Optical Properties of Nanocrystalline (K0.34Na0.65)NbO3.01Thin Films Deposited by RF Sputtering
P. Mahesh, D. Pamu
Department of Physics, Indian Institute of Technology Guwahati, Guwahati – 781039, India.
received October 15, 2013, received in revised form December 11, 2013, accepted January 14, 2014
Vol. 5, No. 1, Pages 23-30 DOI: 10.4416/JCST2013-00026
Abstract
(K0.34Na0.65)NbO3.01(KNN) thin films were deposited at ambient temperatures by means of RF magnetron sputtering. The X-ray diffraction patterns (XRD) reveal that the as-deposited films are amorphous and on annealing at 500 °C for 1 h induced nanocrystallinity with improved microstructure and optical properties. The crystallite size in the films varies between 44 and 20 nm and is dependent on both O2 SCCM and the thickness of the films. The annealing process increased the grain size along with the roughness in the films. It is observed that the amorphous films exhibited higher band-gap energies (3.5 – 3.9 eV) and lower refractive indices (1.82 – 2.01 at 600 nm). On the other hand, the annealed films exhibited smaller band-gap energies (3.46 – 3.78 eV) and higher refractive indices (1.88 – 2.13 at 600 nm), which is attributed to the improvement in the crystallinity and microstructure of the films. Further, the hardness (1.54 – 10.74 GPa) and elastic modulus (17.8 – 80.3 GPa) are significantly affected by the O2 SCCM and annealing temperature. It is found that both the optical and mechanical properties of the KNN films are profoundly influenced by the crystallinity, average particle sizes, packing densities and O2 SCCM.
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Keywords
Thin films, crystal structure, X-ray diffraction, optical properties, mechanical properties
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