Quadrupole and Octopole Electromagnetic Waves in Slightly Non-Uniform Magnetized Plasma Column

Abstract

The effects of substrate temperature on optoelectronic and structural properties of undoped microcrystalline silicon thin films have been investigated. The undoped silicon films have been deposited by the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique using a SiH 4 and H 2 gas mixture at 105 MHz plasma excitation frequency and moderately low power density of 70 mW/cm 2 . The effect of the systematic variation of substrate temperature (from 180 C to 370 C) on film properties has been studied, while keeping the other parameters constant. The deposition rate is considerably high (2.6As À1 ) at 180 C and remains almost constant over the whole temperature range. Dark conductivity for all the films lies around $10 À6 Scm À1 . Low subband gap absorption has been observed by photothermal deflection spectroscopy for these microcrystalline films. Increase of substrate temperature improves the microcrystallinity of the film, which is confirmed from structural studies. Crystalline grain size also increases with increase of substrate temperature and a maximum of 460A has been achieved at 370 C. A satisfactory correlation is observed among the results of different structural studies: Raman spectroscopy, infrared spectroscopy, X-ray diffraction, transmission electron microscopy and atomic force microscopy.

Axial structure of plasma column sustained by non‐symmetric electromagnetic surface wave

“…If this peculiarity is not taken into account, it is possible to obtain nonphysical solutions in the region of the point where k 1 = k 2 . The research carried out has shown that this special point is a point of wave type changing [12].…”

“…For arbitrary values of plasma column radius and external magnetic field value the local dispersion equation (9) can be solved only with the help of numerical methods. The detailed analysis of the local dispersion equation for the wave in m = ±2 and in m = ±3 modes was studied in our previous paper [12]. Here we represent some new data which is necessary for plasma density axial profile study.…”

“…The increase of the parameter Ω leads to the decrease of the SW phase velocity in the region of the small Re(k 3 )R values (Re (k 3 ) R 3.0) and to the increase of the SW phase velocity in the region of the high Re(k 3 )R values. In the case of strong external magnetic field when electron cyclotron frequency ω ce exceeds the generator frequency ω (Ω > 1) the local dispersion equation (9) at the given external magnetic field value, generator frequency plasma density and plasma column radius has a number of solutions that correspond to the eigen waves of the waveguide structure with different axial wavenumbers Re(k 3 )R [12]. Therefore such waves propagate along the plasma column with different phase velocities.…”

“…In the case when external magnetic field is strong (Ω > 1), the wave in m = −2 mode changes its nature from generalized surface mode nearby the generator up to the pseudosurface one at the end of the discharge [12].…”

“…It is necessary to note that the SW possesses the collisional and resonant damping increased with the increasing of azimuth wavenumber absolute value [3,4,10]. But modes with rather high azimuth wavenumbers m (m > 3) are strongly damping modes with low power fluxes [12]. So, it is possible that they are slightly suitable for the sustaining of rather long discharges.…”