Abstract
In this paper, TixFeCoNi (x = 0, 0.5, 1.0) alloy targets were prepared by an arc melter, and Ti element was designed as a variable. The alloy films were prepared by a vacuum DC magnetron sputtering. The influence of the microstructures on the electrical properties and magnetic properties were investigated under different heat treatment conditions and oxygen atmosphere. The microstructures of the TixFeCoNi films after annealing at high temperature of 1000°C was studied to understand the relationship between the resistance and the microstructure of TiFeCoNi oxide film which had a very low resistance of 35 μΩ-cm, also the thermodynamics of this stratification phenomenon and electrical and magnetic correlation were discussed. Second, the TixFeCoNi oxide films were made in situ though an oxygen atmosphere under different oxygen flow rate, also the microstructure, electrical and magnetic properties of the anoxic oxide were investigated. This method could improve the application of these thin films and reduce the cost of production. This paper is divided into six chapters: Chapter 1 is introduction which describes the research background and motivation, including the basic structure of TiFeCoNi film, electrical advantages and challenges. Chapter 2 is literature and theoretical basis, such as high entropy alloy film research and development, film conductivity and magnetic theory. Chapter 3 is experimental steps and analytical methods, detailed describes the analysis methods of the microstructures and properties of the thin films, such as X-ray diffraction, scanning electron microscope and transmission electron microscope, electrical analysis, including four-point probe method and Hall effect measurement, and magnetic analysis is the use of vibration sample magnetic measurement. Chapter 4 discusses the annealing effects on the microstructures and properties on the TixFeCoNi alloy films. Chapter 5 studies the method to directly produce Ti0.5FeCoNi oxide films though an oxygen atmosphere, and also their properties. The films were deposited under different oxygen flow rates, without bias and no temperature-controlled, followed by annealing at a high vacuum and rapid annealing furnace at low temperature of 400 °C-1 h. Finally, Chapter 6 summarizes the findings and main contributions of this study. First, the mixed structures of a metal and oxide were the main factor to form a low resistivity. When the films were annealed at high temperature, the diffusion rate of atoms caused the stratification in films. Second, when the films were deposited with a different oxygen flow rates, the films were formed a uniform oxide layer. The resistivity of the films was not as low as expected due to the high oxygen contents. But the film had a saturation magnetization of about 1100 to 2200 emu / cm3 (Equivalent to 1.4 ~ 2.8 Tesla) was observed, and this discovery is also the biggest contribution of this study.