Synthesis and Optical studies of Pure and La/Mn co substituted BiFeO3 thin films

Abstract

Bismuth ferrite (BFO) is a very well-known multiferroic material due to the existence of multiferroic properties at room temperature and is a promising candidate for magnetoelectric applications which makes it very useful for the potential devices. However, it is difficult to synthesize single phase BFO and control leakage current, which restricts its use in commercial applications. Additionally, because of its polycrystalline and porous structure and high leakage current levels, this material is difficult to use commercially. To solve this problem, scientists have been developing new approaches for the synthesis of multiferroic materials based on BFO. Therefore, to achieve the pure phase and to reduce the Bi3+ volatilization issue with minimized porosity and leakage current BFO is doped with La/Mn at A-site and B-site respectively. By using chemical solution deposition technique BFO thin films have been prepared on FTO glass substrates in present work. This thesis presents a detailed investigation of pure, La3+ substituted, Mn3+ substituted and La3+-Mn3+ co-substituted BFO thin films. Detailed study of structural and optical properties have been investigated. It is expected that substitution of La3+ for Bi3+ can control the Bi3+ volatilization. In studies, it can be found that the substitutions of dopants at A and B-site of BFO induce dominant effects in structure and optical properties of BFO. Structure of the prepared films are investigated using XRD and Raman analysis. Optical properties and bandgap studies of all the pure and doped compositions have been carried out within the spectral range of 1.5 eV to 5 eV. Within this spectral range, two d-d transitions and two charge transfer transitions were observed. The change of transitions by addition of dopants at A-site and B-site were studied in detail by calculating various parameters using Tanabe Sugano Diagrams. Identifying the role of dopants in reduction of bandgap values is also part of the present study.