Combinatorial Investigation of Intermetallics Using Electron-beam Deposition

Abstract

We have systematically studied subtle changes in physical properties of intermetallics using the combinatorial strategy where a large number of samples with systematically changed parameters can be rapidly studied. We have developed a new combinatorial electron-beam (e-beam) deposition chamber which allows us to perform layer-by-layer deposition as well as co-deposition. For my thesis, two particular topics of significant technological impacts involving intermetallic systems were investigated. They are exchange-coupled soft/hard magnetic bilayer systems and hydrogen storage Mg-(transiton metal) (TM) binary systems. The first topic is discussed in Chapter 2 - Chapter 4, and the second topic is duscussed in Chapter 5 - Chapter 7. Summary of the thesis work and future plans are discussed in Chapter 8. We have studied the effect of magnetic parameters of the soft layer on the exchange coupling behavior of soft/hard magnetic bilayer systems. The magnetic parameters of the soft layer were systematically changed in a combinatorial manner by changing the composition of the soft layer. The exchange coupling behavior was monitored by M-H hysteresis loops taken by a magneto-optical Kerr effect (MOKE) measurement set up. The MOKE M-H hysteresis loops successfully delineated the exchange coupling behavior dependence on the magnetic parameters. We have also studied the effect of the crystallinity and grain-texturing of the hard layer on the exchange coupling behavior of hard/soft magnetic bilayer systems. The crystallinity and the degree of grain-texturing were controlled by growth temperature and the post-annealing process of the hard layer. The MOKE M-H hysteresis loops successfully revealed that attaining a single phase, single orientation hard layer is the key to achieving a good exchange coupling behavior. We have developed a new infrared (IR) imaging set up to perform high-throughput screening of hydrogen storage properties of Mg-TM systems. In order to demonstrate the utility of the set up, we studied promising Mg-TM binary systems. We have fabricated Mg-TM binary composition spread thin films using the combinatorial e-beam chamber. For each composition, IR intensity as a function of measurement time were monitored by analyzing images collected. The change in IR intensity curves gave systematic trends in hydrogen absorption/desorption properties of Mg-TM thin films.