Realization of high tunability barium strontium titanate thin films by rf magnetron sputtering

Ferroelectric thin films are currently being used to develop tunable microw ave circuits based on the electric-field dependence of the dielectric const ant. (Ba0.5Sr0.5)TiO3 (BST) films prepared by sputtering on Pt/TiO2/SiO2/Si substrates are found to exhibit a capacitance change (tunability) of nearl y 4:1. Higher tunability has been attributed to the (100) texturing of the BST films and is a result of the biaxial tensile stress imposed by Si on BS T making the polar axis oriented in plane. Electrical characterization show s that the dielectric permittivity increases with increase in film thicknes s (up to similar to 200 nm). (C) 1999 American Institute of Physics. [S0003 -6951(99)03646-3].