Atomic Force Microscopy Observation of the Initial Growth Stage and the Ferroelectric Properties of Bi₂VO_5.5 Films on SrTiO₃(100), Si(100) Substrates

The initial growth mechanism of Bi₂VO_5.5 thin films on SrTiO₃(100) has been studied using atomic force microscopy (AFM), and c-axis oriented ultra-thin films have been prepared by laser ablation. The Bi₂VO_5.5 films are constructed at various growth temperatures. The films deposited at 500° C grow by the step-flow mode, whereas the films deposited at 400° C grow by homogeneous nucleation. From these results, it is evident that Bi₂VO_5.5 grows in multiples of 0.8 nm as complete molecular units and that the top-most layer is Bi₂O₂. The dielectric constant of Bi₂VO_5.5 thin films formed on Si(100) is about 35, and a C-V plot of a Bi₂VO_5.5-SiO₂ MIS capacitor subjected to dc polarizing voltages shows memory windows of 0.1 V against a ±2 V gate bias.