Filmes finos de ferrita de bismuto (BiFeO₃) para a produção de dispositivos eletrônicos

Abstract

Materials that exhibit multiple physical properties and/or states, such as multiferroics, have gained significant attention in both academic and industrial circles due to their potential for miniaturization and increased efficiency compared to currently commercialized devices. Among these materials is bismuth ferrite (BiFeO₃) which demonstrates ferroelectric properties at room temperature, and, under certain conditions, also exhibits measurable antiferromagnetic properties. However, when it comes to bismuth ferrite, several challenges remain unresolved, as the formation of secondary spurious phases during deposition, high leakage current density due to defects, and the bulk material's ordering, which inhibits the simultaneous observation of antiferromagnetism and ferroelectricity. Therefore, this work aims to deposit amorphous BiFeO₃ thin films at room temperature using the RF Sputtering technique and subsequently crystallize them through thermal annealing. These films were characterized using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Visible and Ultraviolet Spectrophotometry (UV-Vis) and Fourier Transform Infrared Spectroscopy (FT-IR). The goal is to better understand the deposition process, analyze the optical, chemical, morphological and structural properties of the deposited films aiming, if possible, to improve the quality of the films for future use in device manufacture. As a key result, significant differences were observed in the formation of spurious phases and the crystalline orientation of the BiFeO₃ thin films. Deposition with the appropriate gas ratio, such as 60:40 of Ar:O₂, favored the crystallinity of BiFeO₃. The crystalline structure refinement using the Le Bail method showed a good match between experimental data and the theoretical model, reflected in satisfactory χ² values, demonstrating the structural quality of the films. Additionally, the films exhibited an average optical band gap of 2.3 eV, further reinforcing their potential for technological applications, such as in electronic devices, sensors, and solar cells. The multiferroic properties of BiFeO₃ make it a promising material for these applications, where precise control of deposition parameters is essential to ensure high structural and functional quality of the material.