Volume 95, Issue 11, 01 June 2004
Index of content:
- PLASMAS AND ELECTRICAL DISCHARGES (PACS 51-52)
Positive and negative polarity current pulse characteristics of a helium glow discharge in a cylinder-plane electrode gap at atmospheric pressure95(2004); http://dx.doi.org/10.1063/1.1707202View Description Hide Description
The positive and negative polarity discharge current pulse forms were examined between steel cylinder- plane electrodes in helium glow and pseudoglow discharges under atmospheric pressure at 10 kHz. The theoretically determined current pulses agreed very closely in form and magnitude with those recorded experimentally. The electronic and ionic charge carrier components comprising the negative polarity current pulse were found to be very nearly equal in magnitude, in contradistinction to the positive polarity pulse, where the electronic charge carrier component was dominant. This larger electronic charge carrier component was reflected in the magnitude of the corresponding photocurrent pulse, which substantially exceeded that of the negative polarity counterpart. The glow discharge regime current pulse forms were also compared to the pulse forms characterizing pseudoglow discharges, also obtained at 10 kHz but at a more elevated voltage, as well as with those recorded at a reduced frequency of 4 kHz but at the same value of applied voltage. Good agreement was also found to exist between the experimentally determined ultrahigh-speed image patterns of the propagating positive and negative discharges and the corresponding calculated electron density contours within the gap.
Lifetime evaluation of weakly ionized plasma channel by accumulation effect of charged particles by means of laser absorption95(2004); http://dx.doi.org/10.1063/1.1715138View Description Hide Description
The density of weakly ionized plasma and the lifetime for laser-triggered lightning are improved by using a KrF excimer laser with a high repetition rate of the order of kilohertz. We have studied how to create a weakly ionized plasma channel with the plasma density of and the long lifetime of the order of milliseconds in order to trigger and guide lightning discharge efficiently. The density of a weakly ionized plasma channel is and the plasma channel has a long lifetime of the order of milliseconds, which were achieved by utilizing the accumulation effect of charged particles generated by the high-repetition-rate laser. Moreover, it is clarified that the dominant mechanism of decay of plasmagenerated the high-repetition-rate laser was ion-ion recombination between and
Structural and optical properties of titanium dioxide films deposited by reactive magnetron sputtering in pure oxygen plasma95(2004); http://dx.doi.org/10.1063/1.1728313View Description Hide Description
Titanium dioxide thin films were deposited on unheated quartz substrates in “pure oxygen” plasma by reactive radio-frequency (rf) magnetron sputtering. The structural and optical properties of depositedfilms were systematically studied by changing the deposition parameters, and it was very recently found that crystalline films grew effectively in pure atmosphere. For filmsdeposited at a rf power of 200 W, x-ray diffraction patterns show the following features: (a) no diffraction peak was observed at a total sputtering pressure of 1.3 Pa; (b) rutile (110) diffraction was observed at 4.0 Pa, (c) the dominant diffraction was from anatase (101) planes, with additional diffraction from (200), under between 6.7 and 13 Pa. For the deposition at 140 W, however, crystalline films with mixed phases were observed only between 4.0 and 6.7 Pa. The peaks of both the deposition rate and the anatase weight ratio for the films produced at 140 W were found at of approximately 6.7 Pa. This suggests that the nucleation and growth of films were affected by the composition, density, and kinetic energy of the particles impinging on the substrate surface. The optical absorption edge analysis showed that the optical band gap and the constant B could sensitively detect the film growth behavior, and determine the filmstructure and optical absorption. The change in the shape of the fundamental absorption edge is considered to reflect the variation of density and the short-range structural modifications.
95(2004); http://dx.doi.org/10.1063/1.1715133View Description Hide Description
In the past, computer-aided simulation of sputtering magnetron has been applied mainly to planar cathodes with flat target surfaces. In this work, we have simulated the target erosion profile of a cylindrical rotary magnetron by tracing electron trajectories and predicting ionization distribution. The electric potential is prescribed as a radial function. A fourth-order Runge–Kutta method is used to solve the electron movement equations, and a Monte Carlo method is employed to predict electron/Ar collision. It is shown that the simulation can predict the target erosion with reasonable accuracy.