Synthesis of nanoparticles in microplasma reactor

Synthesis of silicon-based nanoparticle has been studied in capacitively coupled VHF (144 MHz) microplasma reactor. A mixture of He/H$_{2}$/TEOS(Tetraethoxysilane) was processes in a 470 $\mu $m capillary tube. The process starts with the creation of supersaturated radical condition, followed by homogeneous nucleation, cluster formation and/or particle growth, and annealing including aggregation of particles. The proposed microplasma reactor has several advantages over these processes: (1) Microplasma under high frequency operation easily provides supersaturated environment regardless of thermodynamic equilibrium (Ne$\sim $4$\times $10$^{15}$cc$^{-1}$ at T$_{rot}\sim $1800K), (2) Micrometer scale reactor equalizes radical density and temperature, realizing uniform nucleation, (3) Charged particles prevent aggregation, (4) Particle synthesis due to consecutive reaction is easily optimized with short-residence time reactor ($\sim \mu $s). Optimum gas mixture such as He/1000sccm, H$_{2}$/1sccm, and TEOS/(less than 100 ppm) deposited 50 nm particles on a substrate. Detailed analysis of those particles is now being conducted. * This work has been supported by the Grants-in-Aid for Scientific Research on the Priority Area of Microplasmas from the Japanese Ministry of Education, Culture, Sports, Science and Technology.