Metal organic decomposition technique and optical propertiesof amorphous Ba0.7Sr0.3TiO3 thin films

With the development of Si-based optical integrated circuit, much attention has been paid to the crystalline and amorphous (BaxSr1-x)TiO3(BST) films due to its good optical properties. In this study, the amorphous Ba0.7Sr0.3TiO3 (BST0.7) thin films were grown on the fused quartz and silicon substrates at low temperature by using a metal organic decomposition (MOD)-spin-coating procedure from barium 2-caprylate Ba(C8H15O2)2 and 3-methylbutyl acetate CH3COOC2H4CH(CH3)2-based special precursors. The optical constants of amorphous BST0.7 thin films including refractive index, extinction coefficient and optical band gap energies were presented. Photoluminescence spectra of BST0.7 films were also observed. The calculated extinction coefficient of 214-nm-thick amorphous BST0.7 thin films in visible and near-infrared region was of the order of 10-3, which is much lower than that of polycrystalline BST thin films. The optical band gap energy and refractive index n were estimated to be about 4.27 eV and n=1.94, respectively. Intensive photoluminescence at room temperature was achieved in the 520 to 610 nm wavelength range with a strong visible peak at 540—570 nm when excited by 450 nm laser light. No photoluminescence was observed in crystalline BST0.7 thin films.