Duck Kyu Park

Anomalous hard x-ray emission mode in a plasma focus discharge with hydrogen-argon mixtures

We observed an anomalous discharge mode causing explosive surface evaporation and emission of hard x rays of 10–40 keV in the regime of the lower hydrogen partial pressures of hydrogen–argon mixture in a Mather type plasma focus device of 1.5 kJ. At the anomalous mode, the x rays were emitted from only the surface of the anode without emissions from a plasma column or hot spots, accompanying with explosive evaporations of the anode surface.

Correlations between Argon Ion Beams and X-Rays in a Plasma Focus

We investigated the characteristics of X-rays and ions generated in a argon plasma focus discharge, and analyzed the correlation between X-ray emissions and ion emissions using the time of flight method composed with a Faraday cup, a capacitive current monitor, and p–i–n diodes covered with Ross filters. We obtained the energy spectra of argon ion beams, and observed X-rays of Ar Kα line and Cu Kα line. The optimum pressure range for ion emissions agreed with that for X-ray emissions, and ion energy distributions were shifted toward higher energies when X-ray emissions were good, which means the enhancement of the ion acceleration due to the mechanism of X-ray emission. The observed time correlations can not be explained by conventional ion acceleration models, but by a hybrid model describing the electric field induced by the moving current distribution, an anomalous resistivity, and the Hall effect.

Indium zinc oxide films deposited on PET by LF magnetron sputtering

Indium zinc oxide (IZO) has attracted much attention recently for use in transparent oxide films compared with the ITO film. We carried out the deposition of IZO on a polyethylene terapthalate (PET) substrate at room temperature by a low-frequency (LF) magnetron sputtering system. These films have amorphous structures with excellent electrical stability, surface uniformity and high optical transmittance. The effects of LF applied voltage and O2 flow rate were investigated. The electrical and optical properties were studied. At optimal deposition conditions, thin films of IZO with a sheet resistance of 32 Ω/sq and an optical transmittance of over 80% in the visible spectrum range were achieved. The IZO thin films fabricated by this method do not require substrate heating during the film preparation of any additional post-deposition annealing treatment. The experimental results show that films with good qualities of surface morphology, transmittance and electrical conduction can be grown by the LF magnetron sputtering method on PET which is recommendable.

Influence of Oxygen Flow Rate on the Properties of ITO Films Prepared by Low-Frequency (60 Hz) Magnetron Sputtering

In this study, indium tin oxide (ITO) films were deposited at 300°C on glass substrates by low-frequency (60 Hz) magnetron sputtering technique. The influence of oxygen flow rate on the structural, electrical and optical properties of ITO thin films was investigated. The oxygen flow rate was varied from 0 to 8 sccm. We obtained the most superior property of ITO films at oxygen flow rate of 0.5 sccm. The films are found to show preferential orientation both (222) and (400) planes in the XRD patterns. The resistivity of the films with the thickness of 140 nm is 2.1 × 10−4 ohm · cm with 88% optical average transmittance in visible range (500–800 nm). Therefore, we conclude that transparent conducting ITO films prepared by low-frequency magnetron sputtering can be applied for various flat panel displays.

Properties of Indium Tin Oxide on Polymer Films Deposited by Low-Frequency Magnetron Sputtering Method

In this study, we introduce indium tin oxide (ITO) thin films grown by using low-frequency (60 Hz) magnetron sputtering method. Characteristics of the ITO thin films deposited on polyethersulfone (PES) substrates are investigated. Experiments were carried out as a function of deposition time and substrate temperature. ITO thin films on PES substrate revealed amorphous structure. The optical transmittance, the sheet resistance and the resistivity of the films decreased with the increasing deposition time. The sheet resistance and the roughness of the films increased with the increasing substrate temperature. Roughness values of ITO films on PES substrate deposited at various substrate temperatures are Ra (<2 nm), Rms (<3 nm) and Rp-v (<10 nm). The experimental results confirm that the films with good qualities in surface morphology, transmittance and electrical conduction can be grown by a low-frequency magnetron sputtering method.

X-Ray Radiation of the Plasma Focus with Inverse Pinch Switch

X-ray radiation characteristics of the plasma focus with inverse pinch switch was investigated. The plasma focus device power with capability of 20 kJ contains a 40 kV condenser power supply and adopts a new type of switch system, The mechanism of X-ray radiation was analyzed using a pair of detectors. The variation of X-ray radiation as a function of the position of emitted X-ray and the shape of electrode was examined closely using the time-integrated method. By analyzing the mechanism, we found that the X-ray radiation has three peaks in the optimal plasma focus condition with the middle one being m=0 instability.

Characteristics of ITO Thin Films for Organic Light Emitting Diode by using a Low-Frequency Magnetron Sputtering Method

In this study, we have tried the growth of indium tin oxide (ITO) thin films by using low-frequency magnetron sputtering method (LFMSM). Characteristics of ITO thin films deposited on polyethersulfone (PES) and polyetyleneterephthalate (PET) substrates are investigated. Experiments were carried out as a function of deposition time. With increasing the deposition time of the ITO thin films on PES substrate, the sheet resistance is decreased. ITO thin films on polymer substrates were amorphous structure.

Effects of Heating on the Hanbit Mirror Plasma

The Hanbit plasmas with densities in the 1012 cm-3 range, are produced by applying 200 kW of pulsed RF power at 3.5 MHz to a slot antenna and 85 kW at 3.75 MHz to a double half turn (DHT) antenna. Experiments have been performed in the Hanbit device to determine the effect of ion cyclotron resonance frequency (ICRF) heating on the ion pitch angle distribution, end loss ion currents, and the total temperature. The ion velocity distribution function is approximated by a Bi-Maxwell distribution with two effective temperatures, parallel and perpendicular to the magnetic field. The ICRF heating affects the pitch angle distribution directly and is a main cause of the anisotropy of the ion distribution. The ions heated by the ICRF are generally either trapped and reflected near the resonant magnetic field or are untrapped and eventually disappear into the loss cone. For ICRF in resonant fields the ion loss into the end regions is lower than that with non-resonant fields even in the absence of plugging. The pitch angle distribution in the central cell is measured using a small Faraday cup and the end loss ions in both end regions using end loss energy analyzer (ELA).

Properties of Indium Zinc Oxide Films on Various Polymer Substrates Deposited by Low-Frequency 60 Hz Magnetron Sputtering Method

We introduce indium zinc oxide (IZO) thin films grown at room temperature by using a low-frequency (LF) 60 Hz magnetron sputtering system. The flexible substrates are PES, PET and PC. The optical, electrical and structural properties of IZO films on flexible substrates were investigated. The alloy target was In2O3:ZnO (90:10 wt%) with a diameter of 3 inch and thickness of 5 mm. The vacuum chamber was evacuated down to pressure 5 × 10−6 torr prior to deposition. The flow rates of argon gas (99.999 %) were kept at a constant value of 30 sccm by a mass flow controller(MFC). The discharges were performed by power of 300 V, 310 V, 320 V. They have low sheet resistance of about 30 Ω/sq., high transmittance of over 85 % in the range of 400–700 nm. Also they showed good band gap of about 3.43 eV on polyethersulfone (PES) substrates, 3.50 eV on polyethylene terephthalate (PET) and 3.30 eV on polycarbonate (PC). The experimental results imply that the films with good qualities in surface morphology, transmittance and electrical conduction can be grown by a low-frequency magnetron sputtering method an PES is the most recommendable substrate.