Controlling oxygen vacancies in BiFeO3 thin films via pyrolysis temperature and O2 annealing

Abstract

Bismuth ferrite (BiFeO3) is a promising material for developing the next generation of multifunctional electronic devices. However, the production of high-quality BiFeO3 thin films is compromised by the tendency for structural and electronic defects to form during synthesis, which degrades their functional properties. In this work, BiFeO3 thin films were prepared by chemical solution deposition to determine optimal conditions for minimizing oxygen vacancies and to evaluate the impact of these point defects on their physical properties. The films were pyrolyzed at 300 ◦C for 60 min and 360 ◦C for 10 min, and crystallized in air and in an O2 atmosphere, at 600 ◦C and 640 ◦C for 40 min. High oxygen vacancies were observed in films prepared at low pyrolysis temperatures and crystallized in air, whereas oxygen vacancies were minimized in the film pyrolyzed and crystallized at high temperatures in an O2 atmosphere. The oxygen vacancies markedly affected the films’ physical properties, leading to increased dielectric loss, dielectric dispersion, dc conductivity, and leakage current, with consequent degradation of photovoltaic and magnetic performance. These findings highlight the critical importance of controlling synthesis parameters to suppress oxygen vacancy formation and achieve high-quality BiFeO3 thin films.