Characteristics Of Vertical Spatial Distribution Of Dust Particles In Radio-frequency-plasma Sheath

The physical characteristics of the plasma sheath formed on the surface of the material and the distribution of dust particles suspended in the sheath directly affect the properties of the processed material in the process of synthetic film and etching,plasma material surface modification and so on.The density distribution of charged particles,the energy distribution,the density of dust particles,the distribution of electric and magnetic fields in the sheath all affect the interaction between the plasma and the processed material.Therefore,it is of great value and significance to study the sheath and dust particles in the sheath.In the capacitively coupled RF discharge plasma experiment,we observed that dust particles were distributed on the power electrode,that is,in the plasma sheath.The plasma sheath is a non-electrically neutral region between the plasma and the wall.The formation of the sheath is because electrons move faster in the plasma than ions,making the plasma positively charged relative to the wall.The generation of dust particles in the sheath is divided into two stages:(1)the dust particles are gradually generated from the reaction gas,when the number of dust particles becomes smaller and the size becomes larger;(2)the stable stage in which the size and number of dust particles no longer change,and the dust particles vibrate back and forth at a certain equilibrium position in the sheath.This thesis mainly studies the distribution of dust particles in the sheath in a relatively stable stage.In the RF discharge plasma environment,we found that the distribution shape of the dust particles is similar to the shape of the groove on the power electrode.And the distribution range and the distance from the power electrode depend on the change of discharge power.The results show that the change in discharge power significantly changes the electric field distribution of the sheath,the ion density in the plasma,the surface potential of the dust particles,and the force of the dust particles have changed significantly,which makes the distribution of dust particles in the sheath.The characteristics have changed significantly.By establishing a three-dimensional distribution model of dust distribution,the change in dust distribution with discharge power can be visually observed.The theoretical model of the sheath describes the distribution of the potential of the sheath.According to the OML theory,the charge amount of dust particles with different heights and sizes in the sheath is obtained.Combining the effect of ion drag force on dust particles,we obtained the force situation of dust particles at different heights.The conclusions drawn by the theoretical model explain the distribution of dust particles in the sheath.As a result,the surface increases the discharge power.In the vertical direction of the sheath,the ion drag force plays a major role in the movement of the particles.