Effect Of Viscosity Of Silicone Oil On Surface Aggregation In C₄F₈ Plasma

In order to get clean and byproducts-free nanoparticles and film materials with special electrical, optical and force properties, the deposition and growth of nanoparticles or thin film on polymer liquid substrate have increasingly attracted a great deal of attention recently. However, during depositing nanoparticles and films, the liquid substrates must be exposed to plasma. The interaction between plasma and liquid substrate can not be avoided. As a result, an important and profound scientific problem in cross areas of plasma physics and materials science is raised, which is about the interaction of plasma and soft matter. This important problem, however, is seldom paid attention.When using liquid substrate deposit superfine nanoparticles or films, because of its fluid characteristics, the tangential interaction between solid particles and liquid substrate is small, resulting in a approximate free interface and boundary conditions with free support. Therefore, atoms, cluster, branch-liked aggregation and even the whole film can diffusion, rotate and aggregate freely on liquid surface, which produced many interesting physical phenomena. However, these different aggregation behaviors are mainly attributed to the difference in experimental parameters. The influence of liquid properties and surface state on aggregation behaviors is seldom reported. Therefore, this thesis studies the effects of viscosity of silicone oil on particle aggregation behavior.This thesis studies the effects of viscosity on particle aggregation behavior on silicone oil with viscous coefficient of 20 mm~2/s, 50 mm~2/s, 100 mm~2/s, 350 mm~2/s and 500 mm~2/s, which are treated in C4F8 dual-frequency capacitively coupled plasma. It is found that the branch-liked fractal structure, repation aggregation, comb structure, disc condensed structure, and sinusoid curve condensed structure can be appeared after C4F8 plasma processing, which depends on viscosity of silicone oil and processing power. Under higher plasma density and lower ion bombardment energy, silicone oil liquid surface appeared branch-liked C: F fractal aggregation structure. With the viscous coefficient increasing from 100 mm~2/s to 500 mm~2/s, the fractal dimension decreases from 1.69 to 145, and the aggregation behavior changes from diffusion-limited condensed aggregation (DLA) to clusters - clusters - aggregation (CCA). At lower plasma density and higher ion bombardment energy, the reptation aggregation structure appears on the silicone oil surface. With the viscous coefficient increasing from 20 mm~2/s to 500 mm~2/s, the radial dimensions of reptation aggregation pipe increases from 1.4μm to 5.4μm, and the orientation of the repation aggregation pipeline changes from partly order to disorder. The formation of repation aggregation structure may result from the temperature gradient of liquid silicon oil surface and bottom due to the plasma interaction.