“…Then the grid is covered by a diamond-like carbon thin film for more than 10 h during diamond deposition in CH 4 /H 2 plasma (see ref. 22). Before this grid was installed in the device shown in Fig.…”
Rubbing angle between rubbing direction and electrode of In-plane switching (IPS) mode, is a key factor deciding liquid crystal behavior. We have derived the solution of liquid crystal (LC) motion of non-zero rubbing angle under weak electric field for IPS mode. Dependence of electro-optical characteristics on rubbing angle of non-negligible size was analyzed.
“…Then the grid is covered by a diamond-like carbon thin film for more than 10 h during diamond deposition in CH 4 /H 2 plasma (see ref. 22). Before this grid was installed in the device shown in Fig.…”
Rubbing angle between rubbing direction and electrode of In-plane switching (IPS) mode, is a key factor deciding liquid crystal behavior. We have derived the solution of liquid crystal (LC) motion of non-zero rubbing angle under weak electric field for IPS mode. Dependence of electro-optical characteristics on rubbing angle of non-negligible size was analyzed.
The combined effects of the variation of hydrogen pressure (40–400 mTorr) and exciting frequency (13.56–50 MHz) on the electron energy probability function (EEPF) and other plasma parameters in capacitively coupled hydrogen H2 discharge at fixed discharge voltage were investigated using rf-compensated Langmuir probe. At a fixed exciting frequency of 13.56 MHz, the EEPF evolved from Maxwellian-like distribution to a bi-Maxwellian distribution when the H2 pressure increased, possibly due to efficient vibrational excitation. The electron density largely increased to a peak value and then decreased with the increase of H2 pressure. Meanwhile, the electron temperature and plasma potential significantly decrease and reaching a minimum at 120 mTorr beyond, which saturated or slightly increases. On the other hand, the dissipated power and electron density markedly increased with increasing the exciting frequency at fixed H2 pressure and voltage. The electron temperatures negligibly dependent on the driving frequency. The EEPFs at low pressure 60 mTorr resemble Maxwellian-like distribution and evolve into a bi-Maxwellian type as frequency increased, due to a collisonless (stochastic) sheath-heating in the very high frequency regime, while the EEPF at hydrogen pressure ≥120 mTorr retained a bi-Maxwellian-type distribution irrespective of the driving frequency. Such evolution of the EEPFs shape with the driving frequency and hydrogen pressure has been discussed on the basis of electron diffusion processes and low threshold-energy inelastic collision processes taking place in the discharge. The ratio of stochastic power to bulk power heating ratio is dependent on the hydrogen pressure while it is independent on the driving frequency.
Radial control of the electron temperature gradient is demonstrated in a double plasma device by making use of segmented grid biasing. The plasma produced in the source region is allowed to diffuse into the target region through a single grid as well as through the cassette of multiple grid assembly, under different grid bias conditions. Both electron heating and cooling are observed radially at one location in the target region when a single grid is used. The electrons are cooled down to a temperature of 3.3 eV from 5.1 eV when the grid bias is raised from −25 to 0 V. Similarly, during heating, the electron temperature increases from 4.8 to 7.3 eV when the grid bias is varied between 0 and +20 V. Two different transparencies of grids, 45% transparency (mess-size, m = 0.8 mm ∼ λDe) and 75% transparency (mess-size, m = 2.4 mm > λDe), are used, where the value of λDe ≈ 0.8 mm. The obtained electron energy distribution function suggests that a grid with less transparency is more effective in cooling the electrons because of insignificant energetic electron–neutral collisions in the target region as a sheath in the close vicinity of grid allows only the high energetic electrons to pass through it. The higher transparent grid, on the other hand, produces electron heating as it exerts a negligible influence on the free flow of accelerated high energy electrons to target plasma due to insignificant thermalization. We expanded this concept and, for novelty, applied it to a radially segmented grid assembly of electrically isolated grids, for effectively charging different plasma regions with differently various potentials for exerting a radial control on electron temperature. The results obtained show that a significantly sharp electron temperature gradient is obtained with a typical gradient scale length of LTe∼10 cm in the target plasma region. The outcome of this study may be useful both in plasma processing applications and for studying plasma turbulence in unmagnetized plasmas.
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