Kuo-Feng Chiu

Structural Evolution and Electrochemical Performances of Oxygen Plasma-Treated LiMn2O4 Thin-Film Cathodes

Polycrystalline LiMn 2 O 4 thin films were deposited by radio-frequency (rf) magnetron sputtering followed by annealing at 600°C in air. The films were then treated with an rf-driven oxygen plasma. The crystallization and surface morphology of LiMn 2 O 4 thin films were correlated with rf powers. The treated samples were tested under harsh conditions such as deep discharge to 1.5 V and cycling at an elevated temperature of 60°C to verify the electrochemical performances of the LiMn 2 O 4 cathodes. The oxygen plasma treatments significantly improved the electrochemical properties of LiMn 2 O 4 thin films. The results showed that the plasma treatments not only resulted in surface densification but also induced finer grains in the subsurface region (10-100 nm), which were believed to enhance the stability of LiMn 2 O 4 cathodes.

A comparison of the rapid-annealed FePt and FePd thin films: Internal stress, L1 0 ordering, and texture

Rapid thermal annealing (RTA) techniques have been widely used in materials engineering. Recently, use of RTA has also considered as an efficient way to control the crystal structure and microstructure of the magnetic materials. L1 0 FePt and FePd have been drawn much attention due their remarkable magnetocrystalline anisotropy (> 107 erg/cm3) [1]. Generally, as-prepared FePt and FePd thin films at ambient temperature are chemically disordered and soft magnetic properties. RTA has been used to improve ordering transformation and control crystal orientation as well as surface morphology of the L1 0 FePt films. However, there are few reports focusing on the L1 0 -FePd films annealed by RTA. In this work, we aim to investigate the difference in crystal structure and magnetic properties between FePt and FePd thin films using RTA. The preferred orientation, L1 0 ordering and initial stress of the FePd and FePt films were compared and discussed.