Research On Characteristic Of Low-Temperature Plasma Magnetic Sheath

Plasma sheath plays an important role in the technique of plasma. Researching characteristic of plasma sheath has very important sense in controlling plasma sheath environment and promoting development of plasma process. There are some problems in these research works. First, the effects of magnetic field cannot be ignored. But the introduce of magnetic field makes the problems more complication. The research work about plasma magnetic sheath has not been developed enough. The characteristics of parameters, which affect the plasma deposition and etching directly, have not been discussed in detail. Second the research work about the effects of negative ions on the sheath structure has very import meaning also. Third, radio frequency discharged has more widely application than dc discharge. The characteristic of RF sheath, the action of elections and ions in the sheath decide the quality of productions directly. Until now there is seldom research work on the RF plasma magnetic sheath. Forth charged dust grains exist widely in Space, laboratory as well as industrial plasma devices. The existence of dust grains could change the characteristic of plasma sheath evidently, and pollute process materials. Knowing and controlling the motion of dusts in the plasma sheath, would be properties to use and eliminate dusts, as well as to solve the problems of realizing control process with external magnetic field.In allusion to these problems, a plasma sheath model in an oblique magnetic field, which has one dimension coordinate space and three dimensions speed space, has been build. The structure of electrostatic plasma magnetic sheath and electronegative plasma magnetic sheath are numerical simulated by fluid method. The characteristic of the sheath and the effects of the magnetic field have been discussed. After that, the research work of DC plasma magnetic sheath has been expanded to the RF plasma magnetic sheath, which is widely used. In the end, the characteristic of dust grains in the plasma sheath, which in an oblique magnetic field, has been investigated by fluid method and sing particle method respectively. The effects of magnetic field on the structure of the dust plasma sheath, on the motions and equilibrium position of dust grains, on the dust crystals, have been analyzed.The results show that the Lorentz force of magnetic field changes the motion status of charged particles (here mainly are ions and dusts). Roughly speaking, when fhe magnetic field is weak, electrons are magnetized while ions are weakly magnetized. When themagnetic field is strong, electrons and ions are magnetized while fine particles are not magnetized. When the magnetic field is ultra-strong, dust particles are weakly magnetized. The magnetic field in z direction (parallel to the board) is the main reason for changing sheath structure. The existence of negative ion has effects on positive ion density distribution because of interaction of particles. Without magnetic field, potential of the RF sheath makes a periodicity cosine change with the time, and the electrons in the plasma sheath answer the external instantaneous RF field. When the external RF frequency is much bigger than ion plasma frequency, ions answer average field. While the external RF frequency is much smaller than ion plasma frequency, Ions answer external instantaneous RF field. With magnetic field, in the region near the electrode, whether ion density distribution answers the instantaneous RF field depends on the ratio of frequency, while in the region near the plasma, the change of ion density distribution is similar to the solution of electrostatic plasma magnetic sheath. Ion departure angle changes periodicity, and increases with the magnetic field in parallel board direction. With the effects of Lorentz force, dusts density distribution changes. The suspended position of dust particles in the magnetic plasma sheath is away from the board while the parallel value of magnetic field increases. The decisive factor of dust crystal structure is system energy. As we all know, the syste...