Chang Koo Kim

Electrodeposition of Manganese-Nickel Oxide Films on a Graphite Sheet for Electrochemical Capacitor Applications

Manganese-nickel (Mn-Ni) oxide films were electrodeposited on a graphite sheet in a bath consisting of manganese acetate and nickel chloride, and the structural, morphological, and electrochemical properties of these films were investigated. The electrodeposited Mn-Ni oxide films had porous structures covered with nanofibers. The X-ray diffractometer pattern revealed the presence of separate manganese oxide (γ-MnO2) and nickel oxide (NiO) in the films. The electrodeposited Mn-Ni oxide electrode exhibited a specific capacitance of 424 F/g in Na2SO4 electrolyte. This electrode maintained 86% of its initial specific capacitance over 2000 cycles of the charge-discharge operation, showing good cycling stability.

Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures using cobalt ammonium sulfate as a structure-directing agent

Hydrothermal synthesis of one-dimensional tungsten oxide nanostructures was performed using cobalt ammonium sulfate as a structure-directing agent, and the effect of the concentration of cobalt ammonium sulfate on the characteristics of the tungsten oxide nanostructures was investigated. XRD measurements showed that hexagonal tungsten oxide (h-WO3) structures were obtained at a higher concentration of cobalt ammonium sulfate (0.2 M), while cubic tungsten oxide (c-WO3) structures were obtained at a lower concentration of cobalt ammonium sulfate (0.01M). Mixed structures of h-WO3 and c-WO3 were observed at an intermediate concentration of cobalt ammonium sulfate. Morphological studies revealed that h-WO3 appeared as nanowires with a diameter of about 40 nm and an average length of 1 μm. c-WO3 was shaped in pillar-like nanorods with a diameter of about 30 nm. A red-shift in the UV/Vis absorption peak was observed with different phases of tungsten oxide nanostructures.

A comparative study on a high aspect ratio contact hole etching in UFC- and PFC-containing plasmas

An etching of a SiO2 contact hole with a diameter of 0.19μm and an aspect ratio of 13, using C4F6/Ar/O2/CH2F2 and c-C4F8/Ar/O2/CH2F2 plasmas, was performed for a feasibility test of the use of unsaturated fluorocarbons (UFCs) as an alternative to perfluorocarbon (PFC) gases for a high aspect ratio contact hole etching. The etch profile of the contact hole obtained in the C4F6/Ar/O2/CH2F2 plasma was shown to have 23% lower degree of bowing than that in the c-C4F8/Ar/O2/CH2F2 plasma. The Kelvin and chain contact resistances of the contact holes etched in the C4F6/Ar/O2/CH2F2 plasma were 10-12% higher than those in the c-C4F8/Ar/O2/CH2F2 plasma, but they were within the device spec. The integration of device with 0.1μm design rule using C4F6/Ar/O2/CH2F2 and c-C4F8/Ar/O2/CH2F2 plasmas during the contact hole etching was also conducted, and it was found that etch profiles, metal coverage, and bottom critical dimensions of the contact in the C4F6/Ar/O2/CH2F2 plasma were nearly identical to those in the c-C4F8/Ar/O2/CH2F2 plasma, suggesting that the use of C4F6 gas as an etchant gas for a high aspect ratio contact hole etching can be a good alternative to PFC gases.