Plasma Characterization of Oxygen-Tetramethylsilane Mixtures for the Plasma-Enhanced CVD of SiOxCyHz Thin Films

Tailoring the wettability of glass using a double-dielectric barrier discharge reactor

A double dielectric barrier discharge reactor operated at a low power frequency of 400 Hz and atmospheric pressure was utilized for regulating the wettability of glass surface. The hydrophobic treatment was performed by plasma polymerization of tetramethylsilane (TMS, in argon gas). The obtained results showed that the TMS coatings formed on the glass substrates without oxygen addition were smooth, uniform films with the maximum water contact angle (WCA) of about 106°, which were similar to those obtained by low pressure, high power frequency plasmas reported in the literature. The addition of oxygen into TMS/Ar plasma gas decreased the WCA and induced the formation of SiOSi and/or SiOC linkages, which dominated the existence of Si(CH₂)_nSi network formed in TMS/Ar (without oxygen) plasma.

Ultra-small photoluminescent silicon-carbide nanocrystals by atmospheric-pressure plasmas

Highly size-controllable synthesis of free-standing perfectly crystalline silicon carbide nanocrystals has been achieved for the first time through a plasma-based bottom-up process. This low-cost, scalable, ligand-free atmospheric pressure technique allows fabrication of ultra-small (down to 1.5 nm) nanocrystals with very low level of surface contamination, leading to fundamental insights into optical properties of the nanocrystals. This is also confirmed by their exceptional photoluminescence emission yield enhanced by more than 5 times by reducing the nanocrystals sizes in the range of 1-5 nm, which is attributed to quantum confinement in ultra-small nanocrystals. This method is potentially scalable and readily extendable to a wide range of other classes of materials. Moreover, this ligand-free process can produce colloidal nanocrystals by direct deposition into liquid, onto biological materials or onto the substrate of choice to form nanocrystal films. Our simple but efficient approach based on non-equilibrium plasma environment is a response to the need of most efficient bottom-up processes in nanosynthesis and nanotechnology.