Modeling the Influence of Nb Concentration on the Structure and Ferroelectric Properties of SrBi₂(Ta₁-xNbx)₂O₉ Films

Abstract

This study examines how varying niobium (Nb) concentrations influence the structural and ferroelectric characteristics of SrBi₂(Ta₁₋ₓNbₓ)₂O₉ (SBTN) thin films. Raman spectroscopy analysis indicates notable shifts and alterations in spectral bands at higher Nb levels (x = 0.5), attributed to distortions in the (Ta,Nb)O₆ octahedral units and a decrease in lattice symmetry. These modifications lead to non-linear changes in the perovskite phase content and remanent polarization, with optimal performance observed at x = 0.1–0.2. The Landau-Devonshire model accurately predicts these behaviors, demonstrating that intermediate Nb doping boosts spontaneous polarization and stabilizes the perovskite phase. However, excessive Nb (x > 0.2) reduces perovskite formation and promotes grain coarsening, diminishing ferroelectric response. These findings highlight the potential of tailored Nb doping in optimizing nanograined SBTN films for non-volatile ferroelectric RAM (NvFeRAM) applications.