Chung-Hyeok Kim

Surface Morphology and Dielectric Properties of SBN Thin Film by RF Sputtering Method

The (SBN) thin films are deposited on Pt-coated electrode(Pt/Ti//Si) using RF sputtering method at various deposition conditions. We investigated the effect of deposition condition on the surface morphology and dielectric properties of SBN thin films. The optimum of the rougness showed about 4.33 nm in 70/30 of Ar/ ratio. The crystallinity and rougness of SBN thin films were increased with the increase of rf power. Also, Deposition rate of SBN thin films was about 4.17 nm/min in 70 W of rf power. The capacitance of SBN thin films were increased with the increase of Ar/ ratio, rf power and deposition temperature respectively.

Improving the Reliability by Straight Channel of As2Se3-based Resistive Random Access Memory

Resistive random access memory (ReRAM) of metallic conduction channel mechanism is based on the electrochemical control of metal in solid electrolyte thin film. Amorphous chalcogenide materials have the solid electrolyte characteristic and optical reactivity at the same time. The optical reactivity has been used to improve the memory switching characteristics of the amorphous As2Se3-based ReRAM. This study focuses on the formation of holographic lattices patterns in the amorphous As2Se3 thin film for straight conductive channel. The optical parameters of amorphous As2Se3 thin film which is a refractive index and extinction coefficient was taken by n&k thin film analyzer. He-Cd laser (wavelength: 325 nm) was selected based on these basic optical parameters. The straighten conduction channel was formed by holographic lithography method using He-Cd laser. Ag + ions that photo-diffused periodically by holographic lithography method will be the role of straight channel patterns. The fabricated ReRAM operated more less voltage and indicated better reliability.

Holographic Properties in Amorphous As-Ge-Se-S with Ag Thickness

In this study, we have investigated the holographic grating formation on Ag-doped amorphous As-Ge-Se-S thin films. The dependence of diffraction efficiency as afunction of Ag layer thickness has been investigated in this amorphous chalcogenide films. Holographic gratings was formed using [P:P] polarized Diode Pumped Solid State laser (DPSS, 532.0 nm). The diffraction efficiency was obtained by +1st order intensity. The results were shown that the diffraction efficiency of Ag/AsGeSeS double layer thin films for the Ag thickness, the maximum grating diffraction efficiency using 60 nm Ag layer is 0.96%.

A Study on the Electrical Strength of Insulating Materials for High-Tc Superconducting Devices

According to the trend for electric power equipment of high capacity and reduction of its size, the needs for the new high performance electric equipments become more and more important. On of the possible solution is high temperature superconducting (HTS) power application. Following the successful development of practical HTS wires, there have been renewed activities in developing superconducting power equipment. HTS equipments have to be operated in a coolant such as liquid nitrogen () or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of some insulating materials, such as unfilled epoxy, filled epoxy, and polyimide in was analyzed. Epoxy is a good insulating material but fragile at cryogenic temperature. The filled epoxy composite not only compensates for this fragile property but enhances its dielectric strength.

Electrical properties of SBT capacitor with top electrodes

The Sr/sub 0.8/Bi/sub 2.2/Ta/sub 2/O/sub 9/ (SBT) thin films are deposited on Pt-coated electrode (Pt/TiO/sub 2//SiO/sub 2//Si) using RF magnetron sputtering method. The electrical properties of SBT capacitors with top electrodes were studied. In the XRD pattern, the SBT thin films in all annealing temperatures had (105) orientation. In the SEM images, bi-layered perovskite phase was crystallized at 750 /spl deg/C and grains largely grew in oxygen annealing atmosphere. The electrical properties of SBT capacitor with top electrodes represents a favorable properties in Pt electrode. The maximum remanent polarization and the coercive electric field with Pt electrode are 12.40/spl mu/C/cm/sup 2/ and 30 kV/cm respectively. The dielectric constant and leakage current density with Pt electrode is 340 and 6.81 x 10/sup -10/ A/cm/sup 2/ respectively.The A Sr/sub 0.7/Bi/sub 2.6/Ta/sub 2/O/sub 9/(SBT) thin films are deposited on Pt-coated electrode(Pt/TiO/sub 2//SiO/sub 2//Si) using RF magnetron sputtering method. The electrical properties of SBT capacitors with top electrodes were studied. In the XRD pattern, the SBT thin films in all annealing temperatures had (105) orientation. In the SEM images, Bi-layered perovskite phase was crystallized at 750/spl deg/C and grains largely grew in oxygen annealing atmosphere. The electrical properties of SBT capacitor with top electrodes represents a favorable properties in Pt electrode. The maximum remanent polarization and the coercive electric field with Pt electrode are 12.40 /spl mu/C/cm/sup 2/ and 30 kV/cm respectively. The dielectric constant and leakage current density with Pt electrode is 340 and 6.81/spl times/10/sup -10/ A/cm/sup 2/ respectively.

Microstructure and properties of SCT thin film by RF sputtering method

The (Sr/sub 1-x/Ca/sub x/)TiO/sub 3/ (SCT) thin films are deposited on Pt-coated electrode (Pt/TiN/SiO/sub 2//Si) using RF magnetron sputtering method. The structural and electric properties of SCT thin films were influenced with substitutional contents of Ca. The composition of SCT thin films were closed to stoichiometry (1.081/spl sim/1.17 in A/B ratio). The maximum dielectric constant of thin film is obtained by annealing at 600[/spl deg/C] of SCT15 thin film. The capacitance characteristics had a stable value below /spl plusmn/5[%]. All SCT thin films used in this study show the phenomena of dielectric relaxation with the increase of frequency, and the relaxation frequency is observed above 200[kHz]. In addition, leakage current increases and breakdown field decreases as a function of deposition temperature.

A study on the dielectric properties of (Sr/sub 1-x/Ca/sub x/)TiO/sub 3/ thin film

The (Sr/sub 1-x/Ca/sub x/)TiO/sub 3/(SCT) thin films are deposited on Pt-coated electrodes (Pt/TiN/SiO/sub 2//Si) using RF magnetron sputtering. The structural and dielectric properties of the SCT thin films were influenced by substitutional contents of Ca. The composition of SCT thin films was close to stoichiometry (1.081/spl sim/1.117 in A/B ratio). The maximum dielectric constant was obtained for a SCT15 thin film. The dielectric constant changes almost linearly in the temperature range -80/spl sim/+90[/spl deg/C]. The temperature properties of the dielectric loss have a stable value. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films is observed above 100[kHz].

Study on the dielectric properties of (Sr.Ca)TiO/sub 3/-based ceramics for the capacitor materials

The dielectric properties of (Sr.Ca)TiO/sub 3/-based boundary layer (BL) capacitor materials were investigated. (Sr.Ca)TiO/sub 3/-based compositions were fired at 1350/spl deg/C in a N/sub 2/ atmosphere to get the based semiconductive ceramics. The Nb/sub 2/O/sub 5/ was chosen for semiconductor of grain. The metal oxides of CuO were printed on the semiconductive ceramics, and those were fired at 1200/spl deg/C for the subsequent grain boundary diffusion. The grain size of the semiconductive ceramics was about 20 /spl mu/m and the apparent permittivity of the resulting material varied between 2/spl times/10/sup 4/ and 3/spl times/10/sup 4/.

Dielectric properties and microstructure of (Sr.Ca)TiO/sub 3/-based boundary layer capacitor materials

The dielectric properties and the microstructure of (Sr.Ca)TiO/sub 3/-based boundary layer (BL) capacitor materials were investigated. (Sr.Ca)TiO/sub 3/-based compositions were fired at 1350/spl deg/C in a N/sub 2/ atmosphere to get the base semiconducting ceramics. The metal oxides of CuO were printed on the semiconducting ceramics and fired at 1200/spl deg/C for the subsequent grain boundary diffusion. The grain size of the semiconducting ceramics was 20/spl sim/40 /spl mu/m and the apparent permittivity of the resulting material varied between 2/spl times/10/sup 4/ and 3/spl times/10/sup 4/.<<ETX>>

Non-linear conduction properties of polytetrafluoroethylene film

To further clarify the carrier behavior of polytetrafluoroethylene (PTFE), the authors studied the nonlinear conduction properties of PTFE film of 50- mu m thickness at temperatures between 20 degrees C and 40 degrees C and with a field intensity between 10 and 400 MV/m. The observed nonlinear conduction properties of the PTFE films varied with the temperature and the electric field and can be explained in terms of conduction phenomena that can be divided into four different regions showing ohmic, Poole-Frenkel, Schottky, and Fowler-Nordheim effects, respectively.<<ETX>>