Enhancing polarization switching, endurance, and fatigue in praseodymium and manganese co-doped bismuth ferrite thin films

Abstract

This study delves into the impact of praseodymium $\left(\mathrm{Pr}\right)$ and manganese $\left(\text{Mn}\right)$ co-doping on electrical, and ferroelectric properties of bismuth ferrite $\left(\text{BFO}\right)$ thin films deposited on fluorine tin oxide $\left(\text{FTO}\right)$ coated glass substrates. The introduction of $\mathrm{Pr}$ and $\text{Mn}$ dopants is found to influence the structure, surface morphology, and optical properties of $\text{BFO}$ thin films. The variations in structure and polarization switching of the fabricated thin film devices, contingent upon the dopant and doping concentration, are investigated. The $\mathrm{Pr}$ and $\text{Mn}$ co-doping changes the optical bandgap of $\text{BFO}$ thin films, as a result of a shift in the absorption spectra. The induced defect states tailor the optical parameters leading to modification in oxygen vacancies. Among the doped samples, $\text{BFO}$ thin film with 7 % $\mathrm{Pr}$ and 3 % $\text{Mn}$ doping exhibited the lowest current density, by three orders of magnitude, attributed to the lowest oxygen vacancy concentration of 29 % inferred from the XPS studies. The effect of doping on the current conduction mechanism and the ferroelectric behavior in $\text{BFO}$ thin film devices is further explored. Structural distortions as a result of co-doping are shown to enhance the remanent polarization of $\text{BFO}$ thin films. It is noted that a maximum structural distortion of 0.07° in 3 % $\mathrm{Pr}$ and 7 % $\text{Mn}$-doped devices resulted in an increment in remanent polarization by approximately $4$ times compared to the pristine BFO thin film devices. Device reliability, endurance, data retention, and fatigue are found to be influenced more by oxygen vacancies than by structural distortion. Thus, oxygen vacancies serve as preliminary indicators of endurance, data retention, and fatigue in $\mathrm{Pr}$ and $\text{Mn}$ doped BFO thin films. Devices containing $7\%\mathrm{Pr}$ and $3\%\text{Mn}$ exhibit improved data endurance and retention over multiple switching cycles, a benefit attributed to a decrease in oxygen vacancies. This study explores the relationship between intrinsic defects and their effects on data retention and fatigue, employing Pr-Mn co-doping as a strategic method to reduce oxygen vacancy defects and enhance device reliability. The $\mathrm{Pr}$ and $\text{Mn}$ doped devices show significant promise for non-volatile memory applications.