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U12.16.1

Ferroelectric Properties in Ca Substituted SrBi2 Nb2 O9 Thin Films Rasmi R. Das, W. Pérez, P. Bhattacharya, and Ram S. Katiyar Physics Department, University of Puerto Rico, San Juan, Puerto Rico 00931-3343

ABSTRACT We have studied the influence of partial substitution of Ca (0%, 5%, 10% and 15%) on the structural and electrical properties of SrBi2 Nb2 O9 (SBN) thin films. Pulsed laser deposition technique was used to grow thin films on platinized silicon substrates. X-ray diffraction data confirmed the polycrystalline nature of the films with preferential orientation along the polarization axis. Incorporation of Ca at Sr-site of SBN reduced the lattice parameter and was attributed to the smaller ionic radii of Ca. The soft mode frequency at 29.5 cm-1 of SBN shifted towards higher wavenumber implied increasing the transition temperature upon Ca substitution. The grain sizes of SBN thin films vary from oval to rod like structures and improving the homogeneous distribution of grains with the increase in Ca contents. The ferroelectric properties of the films enhanced with maximum remanent polarization of 35.3 µC/cm2 . The increase in the coercive field with incorporation of Ca at Sr-site was attributed to the higher electronegativity of Ca. The SBN thin films with the incoporation of Ca exhibited poor leakage current behavior. The reduction of dielectric permittivity with Ca concentration was attributed to the lower dielectric permittivity of CaBi2 Nb2 O9 . INTRODUCTION Ferroelectric thin films of Aurivillius layered compounds have drawn much attention for future non-volatile random access memory (NVRAM) devices [1,2]. In particular, SrBi2 Ta2 O9 (SBT) thin films showed excellent fatigue free characteristics in combination with the low leakage current density (