| Glow discharge hydrocarbon polymer (a-C:H) thin film is in favour of deuterium-tritium ice heating by infrared radiation due to its features such as low-atomic-number, low stress and good infrared permeability. Since, it is an amorphous network structure that it avoids anisotropy and crystal boundary. Based on these advantages, a-C:H thin film becomes the most preferred ablation layer material for Laser inertial confinement fusion (ICF) target.The requirements for surface roughness and defects control of Laser inertial confinement fusion hydrocarbon target are extremely strict. The ICF target is deposited by inductively coupled plasma enhanced polymerization. But currently it seems to meet the bottleneck in control of defects during preparing targets. By simply improving surface morphology through optimization of technical parameters is very difficult. There are many inter-connected technical parameters affecting it, which tremendously increases the workload and complexity. Therefore, the process of growth and formation of defects should be studied in depth. Since the nature of a-C:H thin film deposition is an interactive process for plasma and substrate, the growth of a-C:H thin film is closely related to the components and status of plasma. To break-through the control problem in reducing surface roughness of a-C:H thin film, plasma properties during the process of growth of a-C:H thin film are desired to be studied in depth, which can provides a theoretical guide for a-C:H thin film preparation optimization.In the reacting chamber for the preparing a-C:H thin film, cylindrical and conical quartz tube are usually chosen as the plasma generation chamber. Thus, in this paper, the differences of plasma properties generated in these two kinds of reactors were compared by Langmuir probe and mass spectrometer diagnostic. Moreover the effects of the plasma properties on the process of growth of a-C:H thin film were discussed. This paper discussed the differences and causes for these two a-C:H thin films generated in two chambers from its structures, properties and deposition rates. Based on plasma diagnostic in situ, the influences of radio frequency (rf) power and gas flow ratio on plasma component and status were discussed. It also illustrated the relationship between plasma properties and surface morphology of a-C:H thin film. These studies will provide the basis for the further optimization of preparing technology of a-C:H thin films. Specifically speaking, this thesis includes the following chapters:The significance of a-C:H thin film ablation layer in Laser ICF is described in detail. The gap between China and counterparts abroad in preparing a-C:H thin films was pointed out. The existing problems in a-C:H thin films research field were listed. Based on these problems, the thesis topic and research content were introduced.The technology and principle of inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) in preparing a-C:H thin films were introduced in detail. The principle of Langmuir probe and mass spectrometer were illustrated, and the thin film characterization methods description closed this chapter.In order to figure out the reason why conical reactor performs better than cylindrical reactor in preparing a-C:H thin films, plasma properties in two kinds of reactors were investigated. Firstly, at low pressure, by using probe for radially spatial diagnostic, the radially spatial distribution of plasma parameters at nonlocal electron kinetics were discussed. Secondly, the discharging properties during transition of electron heating mode and electron kinetics in two kinds of reactors were studied. It was found that the radial uniformity of electron density in a conical reactor was better than that in a cylindrical reactor, and a saddle shape formed by central position to Teff distribution direction was observed in a conical reactor. In the meantime, by increasing gas pressure, the transition of EEPFs from Maxwellian distribution to Druyvesteyn-like distribution were observed in both kinds of reactors indicating the transition of electron heating mode from stochastic heating to Ohmic heating. At all of the pressures, the electron density in a conical reactor was higher than the cylindrical one.The component and energy distribution of ions in plasma in these two kinds of reactors were discussed. Using mass spectrometer and probe to diagnose hydrogen plasma in both reactors, the component and energy of ions and parameters of electrons were investigated so as to study their influences on the growth of a-C:H thin films. It was found that there were higher plasma density, deeper dissociation degree and more stable response to rf power, as well as slightly higher plasma density in a conical reactor than that in a cylindrical one.Based on in situ diagnostic of plasma during the process of growth of a-C:H thin film, the structure and properties of a-C:H thin films were investigated under various rf powers and different T2B/H2 gas flow ratios. The influences were studied from following aspects:the deposition rate, chemical component, the structure of functional group, surface morphology and surface roughness. Results showed that there were more second polymerization reactions and more carbon-rich groups at low powers and vice versa. High energy carbon group bombardment induced the concave defects upon the film surface. The minimal root-mean-square roughness was obtained under the rf power of 30 W and the gas flow ratio of 0.6:10.Concludes the full thesis and prospects the future work. |
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