Mi Jung Ji

The improved performance of a transparent ZnO thin-film transistor with AlN/Al2O3 double gate dielectrics

This paper reports on the fabrication of stable and improved performance of transparent ZnO thin-film transistors (TFTs) with AlN/Al2O3 double gate dielectrics. AlN films reduce the surface roughness of the channel/dielectric interface due to an excellent lattice match with the ZnO film. Al2O3 films, which have a large band offset between the channel layers, are helpful to reduce the gate leakage current. Good device characteristics have been obtained from the AlN/Al2O3 TFT with a field effect mobility of 4.3 cm2 V−1 s−1, an on–off current ratio of 2 × 105 and a sub-threshold slope of 0.45 V/decade. By diminishing the charge trap density in the interface, the threshold voltage change from the hysteresis of the transfer characteristics was minimized to 0.3 V. These results should increase the prospects of using transparent TFTs for flat panel display applications.

Crystallinity and Battery Properties of Lithium Manganese Oxide Spinel with Lithium Titanium Oxide Spinel Coating Layer on Its Surface

In this study, lithium manganese oxide spinel (LiMn 1.9 Fe 0.1 Nb 0.0005 O₄) as a cathode material of lithium ion secondary batteries is synthesized with spray drying, and in order to increase its crystallinity and electrochemical properties, the granulated LiMn 1.9 Fe 0.1 Nb 0.0005 O₄ particle surface is coated with lithium titanium oxide spinel (Li₄Ti?O 12 ) through a sol-gel method. The granulated particles present a higher tap density and lower specific surface area. The crystallinity and discharge capacity of the Li₄Ti?O 12 coated material is relatively higher than uncoated material. With the coating layer, the discharge capacity and cycling stability are increased and the capacity fading is suppressed successfully.

Electrochemical Properties of Lithium Secondary Battery and the Synthesis of Spherical Li 4 Ti 5 O 12 Powder by Using TiCl 4 As a Starting Material

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical precursor. Then, the was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at for 30 minutes and at for 6 hours heat treatment time were optimized. was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.