Ki-Woong Whang

Mechanism of high luminous efficient discharges with high pressure and high Xe-content in AC PDP

The mechanism of high luminous efficiency discharges with high Xe content in an AC plasma display panel was analyzed by computer simulation using a two-dimensional fluid model. The model has reproduced well the experimental results. The high luminous efficiency with high Xe content is attributed to high electron heating efficiency as well as high excitation efficiency by electron. The electron heating efficiency is increased with increasing the sustaining voltage under high Xe content and this phenomenon was analyzed by investigating the cathode sheath and secondary electron emission characteristics.

The effects of magnetic fields on a planar inductively coupled argon plasma

The profiles of the magnetic field component of the RF field, the impedance characteristics and the plasma parameters (electron density, electron temperature and plasma potential) of a 13.56 MHz, planar inductively coupled argon plasma were studied in the presence of an external magnetic field and compared with those of the non-magnetized discharge. An efficient RF power transfer and stable impedance matching with a low Q factor of the system could be obtained with the application of a relatively low magnetic field (5 - 20 G) in the pressure range 0.5 - 10 mTorr. The RF magnetic field measurement revealed that the wave excitation was responsible for such improvements. Due to the effective power coupling and improved confinement by the magnetic field, the electron density increased by a factor of two and the plasma potential decreased.

Electron ejection from MgO thin films by low energy noble gas ions: Energy dependence and initial instability of the secondary electron emission coefficient

Low energy ion-induced secondary electron emission from the surface of thin (500–5000 A) polycrystalline MgO films has been investigated with various noble gas ions at energies ranging from 45 to 300 eV. The dependence of secondary electron emission coefficient γi on the type and energy of ions is reported and interpreted in terms of electron ejection mechanisms. As-deposited MgO films showed an initial fluctuation in the secondary emission current, which upon annealing or after a certain ion bombardment time irreversibly disappeared.

Vacuum ultraviolet emission characteristics from He–Ne–Xe gas discharge in an alternating current plasma display panel cell

We measured the time integrated vacuum ultraviolet (VUV) emission spectra of He–Ne–Xe gas mixture from a surface type alternating current (ac) plasma display panel cell. The measured emission lines are the resonance line (147 nm) from Xe*(1s4), the first continuum (150 nm) and the second continuum (173 nm) from Xe dimer excited states. The relative intensities of VUV spectral lines from Xe* and Xe2* are dependent on the He/Ne mixing ratio as well as the Xe partial and total pressure. The intensity of 147 nm VUV increases with the Ne content increase and Xe2* molecular emission increases with the He content increase. Infrared (IR) spectra and the time variation of VUV were measured to explain the reaction pathway and the effect of the mixing ratio of He/Ne on the spectral intensity. A detailed study for the decay time shows that the decay time of 147 nm has two time constants and the radiation of 150 and 173 nm results mainly from Xe*(1s5). The IR spectra shows that the contribution from Xe**(>6 s) to Xe*(...

Two-dimensional modeling of a surface type alternating current plasma display panel cell: discharge dynamics and address voltage effects

To improve the luminance and efficiency of an alternating current plasma display panel, the direct measurement of infrared and vacuum ultra violet (VUV) imaging is performed to study discharge dynamics. Images show two emission regions. One is the cathode glow and the other is the anode glow. In the course of discharge cycle, the cathode glow propagates toward the outer edge of the electrode, while the anode glow does not propagate. We developed a two-dimensional model to simulate the time evolution of the discharge dynamics. We learned from the modeling results that the dominant role for the propagation of the cathode glow is the ion transport and the electron transport for the anode glow. In addition, the effects of address voltage on the luminance and efficiency are investigated during the sustain period. When the address electrode is floating, VUV output is larger than that of biased conditions, but the efficiency decreases slightly. The comparison of 100 V with 0 V bias shows that biased voltage does not affect the luminance and efficiency at the steady state.

Two-dimensional multifluid modeling of the He-Xe discharge in an AC plasma display panel

A numerical analysis of the discharge plasma which forms in an AC plasma display panel cell has been made using time-dependent, two-dimensional multifluid equations to understand the discharge physics of He-Xe discharge. The time dependent distributions of the plasma parameters such as the electron temperature, electron density, various ion densities, and excited state species densities, etc., are obtained during the sustain period in a surface type AC plasma display panel (PDP) cell. Because of its importance in the AC PDP operation, the behavior of the wail charges accumulated on the dielectric surface is also examined. It has been found that a DC bias voltage applied to the address electrode controls the distribution as well as the peak values of the plasma parameters. The reaction analysis showed that the dominant reaction process for Xe ion production is the direct electron impact ionization processes and not the Penning ionization process. The cells which have a smaller electrode gap and larger sustain electrode width could accumulate more wall charges and consequently require less voltage for discharge sustainment.

Inductively coupled plasma heating in a weakly magnetized plasma

A one-dimensional analysis of electron heating process in a weakly magnetized, inductively coupled plasma (MICP) is presented. It is found that the main difference in the heating process of a MICP from that of a usual unmagnetized ICP is in that circularly polarized wave modes can exist in the plasma. The right handed circularly polarized wave (R-wave) can propagate into the plasma and its amplitude can be enhanced by cavity resonance effect at an appropriate chamber length and external magnetic field strength. The enhanced R-wave amplitude can raise the heating efficiency significantly. It is also found that a bounce cyclotron-resonance effect can exist, which, however, is not as significant as the cavity resonance effect.

The Effects of Sustain Electrode Gap Variation on the Luminous Efficacy in Coplanar-Type AC Plasma Display Panel Under Low- and High-Xe Content Conditions

We investigated the effect of sustain electrode gap variation with various Xe content gas in a coplanar-type ac plasma display panel through 2-D numerical simulation to understand the inherent high-luminous-efficacy mechanism. For the low-Xe content gas condition of 5%, the optimal sustain electrode gap was found to be about 200 mum, because of the steep decrease of electric power delivered to electrons with the increase of electrode gap longer than 200 mum. On the other hand, with the high-Xe content gas of 20%, the efficacy continuously increased as the electrode gap increased beyond 200 mum . We have found that the high luminous efficacy under the condition of long electrode gap and high-Xe content gas is due to the high-electron-heating efficacy in the cathode sheath region

Mechanism of Surface Roughness in Hydrogen Plasma‐Cleaned (100) Silicon at Low Temperatures

Surface roughening and defect formation of (100) Si at low temperatures during electron cyclotron resonance hydrogen plasma cleaning are studied in an ultrahigh vacuum environment, and a new model is proposed to explain their mechanisms. The effect of process parameters on surface roughness is quantitatively analyzed by atomic force microscopy and reflection high energy electron diffraction. Crystalline defect morphology is studied by transmission electron microscopy to understand its role in surface roughness. Surface roughness is strongly related to {111} platelet defects at the Si subsurface region and subsequent preferential etching at positions where {111} platelet defects intersect the Si surface. The formation of {111} platelet defects is determined by the subsurface hydrogen concentration, which is determined by incident hydrogen flux and substrate temperature. The preferential nucleation of etching reactions on the {111} platelet may be explained by the classical nucleation theory. Hydrogen ion flux and substrate temperature can be controlled successfully to tailor {111} platelet defect formation and hence, surface roughness.

Low‐temperature silicon homoepitaxy by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition

High quality silicon homoepitaxial layers are successfully grown at 560 °C by ultrahigh vacuum electron cyclotron resonance chemical vapor deposition (UHV‐ECRCVD) using a SiH4/H2 plasma. The effects of substrate dc bias on the in situ hydrogen plasma clean and the subsequent silicon epitaxial growth are examined by the reflection high‐energy electron diffraction (RHEED), secondary ion mass spectroscopy (SIMS), and cross‐section transmission electron microscopy (XTEM). It is observed that the substrate dc bias plays a significant role in obtaining a damage‐free, clean Si substrate prior to epitaxial growth. Severe damage in the Si surface is observed by XTEM, though RHEED shows a streaky pattern, when the substrate is electrically floating, but the damage can be suppressed with +10 V dc bias to the substrate. Substrate dc bias during plasma deposition drastically changes the crystal structure from polycrystalline at −50 V to high quality epitaxial silicon at substrate biases greater than +50 V. Precise con...