Studies on linear and non linear optical properties of pulsed laser deposited Si, SiOx and SiC nanostructured thin films

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The present research work was aimed towards the fabrication and characterization of nc-Si, SiOx and SiC films via PLD technique. The effect of substrate temperature and background gas pressure on their stoichiometry, crystallinity, linear as well as nonlinear optical (NLO) and photoluminescence (PL) properties of these films are studied in detail.The PLD nc-Si thin films were comprised of nc-Si domains embedded in a-Si matrix. The crystallinity as well as optical properties were observed to be influenced by Ts. The SiOx films exhibited change in stoichiometry, x=0.03 to 2.1, as a function of oxygen pressure (10-4 to 0.5 mbar). These films exhibited the micron-sized clusters containing nc-Si embedded in uniform background composed of oxidized amorphous Si. The band gap energy was blue shifted from ~ 1.55 to 2.80 eV with increasing O2 pressure. Laser excited PL spectra with multi-component peaks originated due to quantum confined nc-Si as well as oxygen related defects; NBOH and Vo centers, were observed for oxygen rich SiOx films. Amorphous SiC exhibited a transition from Si-rich SiC to nearly stoichiometric SiC with the increase in Ts (RT to 750 °C) which resulted in decrease in the no from 3.00 to 2.64 and blue shift in the optical band gap from 1.59 to 2.33 eV. The structural disorders in these films tend to decrease with increasing Ts.
Supervisor: Alika Khare