Effects of Non-Stoichiometry and Strain on Ferroelectric Properties of CVD-Grown Bismuth Ferrite Films

Bismuth ferrite (BiFeO3, BFO) is a promising room-temperature multiferroic material but growing high-quality BFO thin films using chemical vapor deposition (CVD) has been challenging due to the limited availability of suitable precursors and the volatility of bismuth. In this study, we successfully grew high-quality BFO thin films using direct liquid injection CVD (DLI-CVD) with a solution mixture of iron acetylacetonate and triphenyl bismuth precursors dissolved in N,N-dimethylformamide. The films were deposited on SrTiO3(001), DyScO3(110), and SrTiO3/Si(001) substrates at 600 °C. The Bi/Fe ratio in the films was precisely controlled by adjusting the molar ratio of the precursors and strategically positioning substrates at optimal locations within the deposition chamber. Additionally, the film strain state is established by lattice mismatch with the substrate and controlling the growth mode. We investigated the effects of nonstoichiometry, substrate-induced strain, and crystalline mosaicity on the structural and ferroelectric properties of BFO films. Additionally, we present the results of magnetic measurements for stoichiometric and iron-rich films. Our findings demonstrate the potential of DLI-CVD for growing high-quality BFO films with superior electrical and magnetic properties.