Investigation Of The Instability Of Silicone Oil Liquid Substrate Exposed To Ar Plasma

People always paid great attention to nanoparticle and thin films materials due to the unique electrical, optical, mechanical properties .People often use various types of solid surface as a substrate to deposit ultrafine metal nanoparticles and thin films. Recently, to obtain the size-controllable, clean and without byproducts nanoparticles, the deposition of ultrafine metal nanoparticles on the low-vapor-pressure liquid surface is increasingly paid attention. The silicone oil and ionic liquid have been used as the liquid substrates to deposit the iron (Fe), silver (Ag) and gold (Au) nanoparticles, and the Fe thin films. The aggregation of Ag and Fe clusters with the branch or disk-shape patterns were obtained. Usually, the difference in the aggregation behaviors was mainly attributed to the different processing parameters. The effect of liquid surface state on particles aggregation is seldom paid attention.On the liquid surface, the formation of nanoparticles is the result of two-dimensional random migration of particles, due to the migration of two-dimensional random particle mean square displacement <Δr2> for the formula <Δr2> = 4kTF-1Δt, the aggregation of nanoparticles on the liquid surface ,depends on the friction coefficient, temperature and time. When silicone oil and ionic liquid have been exposed to plasma, silicone oil will inevitably be effect by plasma including the bombardment of energetic ions on the silicone oil liquid surface,the interactions between plasma and silicone oil liquid. These effects may lead to temperature fluctuations and structure changes on the silicone oil surface, thus affecting the formation of nanoparticles on the silicone oil surface. As a result, When silicone oil is exposed to plasma, the stability of silicone oil is a very important factor affecting the depositing nanoparticles on silicone oil liquid substrate.This paper investigates the structure property of silicone oil exposed to Ar plasma, Using dual-frequency capacitively coupled plasma (DF-CCP) system, the decoupling of two sources made the plasma density and ions energy controlled independently by the high-frequency (HF) and low-frequency (LF) powers respectively. The effect of plasmas on structural properties of the silicone oil liquid substrates is studied. At the action of energetic Ar ions, the surface of silicone oil liquid substrate exhibits a branch-like fractal aggregation structure, which is related to the structure evolution of silicone oil molecule from Si-O chain to Si-O network. The radicals from the dissociation of silicone oil molecule into the Ar plasma make the plasma become a reactive environment. Therefore, the structural evolution of silicone oil liquid substrate and the reactive radicals in the plasma space are the possible factors affecting the aggregation of nanoparticles and the structure and compositions of nanoparticles.