The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field(B_(ex)) along the axis is observed in a range from 0 Gs to 250 Gs(1 Gs = 10^(-4) T), where the electron density varies from 0.5×10^(16) m^(-3) to 9×10^(16) m^(-3).When Bex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When Bex is located in the middle of the antenna, moreover, an effective resistance(R_(eff)) peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece–Gould(TG) wave. It is suggested that B_(ex) is located in the middle of the antenna to obtain a higher efficiency of power transfer.
To reduce the thermal shrinkage of the polymeric separators and improve the safety of the Li-ion batteries,plasma treatment and plasma enhanced vapor chemical deposition(PECVD)of SiO_x-like are carried out on polypropylene(PP)separators,respectively.Critical parameters for separator properties,such as the thermal shrinkage rate,porosity,wettability,and mechanical strength,are evaluated on the plasma treated PP membranes.O_2 plasma treatment is found to remarkably improve the wettability,porosity and electrolyte uptake.PECVD SiO_x-like coatings are found to be able to effectively reduce the thermal shrinkage rate of the membranes and increase the ionic conductivity.The electrolyte-philicity of the Si Ox-like coating surface can be tuned by the varying O_2 content in the gas mixture during the deposition.Though still acceptable,the mechanical strength is reduced after PECVD,which is due to the plasma etching.
The plasma parameters in ICP-CVD system with internal low inductance antennas(LIA) were diagnosed by Langmuir probe.The ions density(Ni) reached 10^(11)-10^(12) cm^(-3),and the electron temperature(T_e) was below ca.2 eV,which was slightly decreased with applied power.A p-type hydrogenated microcrystalline silicon(μc-Si:H) film was prepared on glass substrate.After optimization of the processing parameters in flow ratio of SiH_4:B_2H_6:H_2,a high quality μc-Si:H film with deposition rate above 1.0 nm/s was achieved in this work.
In this work,the reversal of radial glow distribution induced by reversed magnetic field is reported.Based on the Boswell antenna which is symmetric and insensitive to the magnetic field direction,it seems such a phenomenon in theory appears impossible.However,according to the diagnostic of the helicon waves by magnetic probe,it is found that the direction of magnetic field significantly affects the propagation characteristic of helicon waves,i.e.,the interchange of the helicon waves at the upper and the lower half of tube was caused by reversing the direction of magnetic field.It is suggested that the variation of helicon wave against the direction of magnetic field causes the reversed radial glow distribution.The appearance of the traveling wave does not only improve the discharge strength,but also determines the transition of the discharge mode.
