Investigating structural features of Ba and Zr co-substituted strontium bismuth tantalate thin films

Abstract

Structural (crystal and microstructure), chemical and electronic states, and ferroelectric and electrical features of Ba and Zr co-substituted strontium bismuth tantalate (SBT) were probed in this study. Distinctly, Ba and Zr were substituted for Ta and Sr sites of $\hbox {Sr}_{0.8}\hbox {Bi}_{2.2}\hbox {Ta}_{2}\hbox {O}_{9 }$ in the form of $\hbox {Sr}_{0.8-x}\hbox {Ba}_{x}\hbox {Bi}_{2.2}\hbox {Ta}_{2-y}\hbox {Zr}_{y}\hbox {O}_{9}$. To investigate the impact of the co-substitution on the crystal structure, microstructure, ferroelectric and electrical properties, $\hbox {Sr}_{0.8-x}\hbox {Ba}_{x}\hbox {Bi}_{2.2}\hbox {Ta}_{2-y}\hbox {Zr}_{y}\hbox {O}_{9}$ thin films were deposited on $\hbox {Pt/Ti/}\hbox {SiO}_{2}/\hbox {Si}(100)$ wafers by sol–gel spin by coating method. Crystal structure, microstructure, chemical and electronic states, ferroelectric, capacitance and leakage current characteristics of the films were studied to investigate potential for one transistor type ferroelectric random access memories (1T-type FeRAMs). Successful substitutions up to 10 mol% lead to reduction of double remanent polarization $(2P_{\mathrm{r}})$ to $10.26\,\upmu \hbox {C\,cm}^{-2}$, and dielectric constant $(\varepsilon _{\mathrm{r}})$ to 135. These values demonstrate that successful co-substitution of limited Ba and Zr in SBT with stable crystal structure has the ability to decrease $P_{\mathrm{r}}$ and $\varepsilon _{\mathrm{r}}$ values of the ferroelectric material which can be a candidate gate to be utilized in ferroelectric field-effect transistors (FeFETs) for 1T-type FeRAM applications.