Synthesis and Characterization of ferroelectric nano crystalline thin films

Abstract

newline Ferroelectric random access memory works on the principle of ferroelectric effect and is used to store the data efficiently. FRAM is a superior memory which has fast speed of reading and writing the data. FRAM is developed by depositing a film of ferroelectric material in crystalline form between two electrode plates to form a capacitor. Two families of materials, perovskite and layered perovskites have been widely studied for memory applications. Bismuth Titanate (BIT) which is a Bi- based layered perovskite ferroelectrics has been selected in the research work to make thin films because of several advantages of Layered- Perovskites such as fatigue free, lead free, low operating voltages and better ferroelectric properties. newlineBut to enhance the performance of BIT thin films, La doped BIT have been investiagted. Lanthanum modified Bismuth Titanate (BLT) has several advantages such as extremely low coercive field, low processing temperature, high remanent polarization, better mechanical strength and minimum field induced polarization switching fatigue. newlineIn this thesis before preparing BLT thin films, bulk ceramic samples have been prepared and analyzed to find the optimum La doping in BIT. Six BLT ceramic samples with different La doping have been prepared using solid state reaction method. XRD analysis and leakage current densities of these ceramic samples were studied and it is found that 75% of La doping in BIT sample has best PE hysteresis characteristics and minimum leakage current density. Further I-V characteristics and SEM have been obtained which confirms that 75% doping is the optimum percentage of La doping in BIT. newlineAfter finding the optimum doping of La, thin film samples of various thickness have been prepared using sol-gel technique. XRD analysis, leakage current density, PE hysteresis loops and fatigue characteristics of these samples have been studied. Here, it newlinehas been concluded that the optimum thickness of the thin film samples is 350 nm which results in low leakage current density,