| Summary: | 博士 === 國立中央大學 === 物理與天文學研究所 === 82 === Fine SiO2 paricles are fabricated through gas phase homogeneous
chemical reactions and nucleations in rf magnetron discharge in
SiH4/O2/Ar gas mixtures. For P>30 mTorr, primary fine particles
(PFPs) with diameter about 20 nm can be formed and their
diameter increases with the system pressure. They can aggregate
with other PFPs to form larger aggregated fine particles (AFPs)
with nearly spherical shape. The size of the AFP depends on the
duration of the rf power. The homogeneous process creates oxide
particles with more relaxed Si-O bonding than the surface-
process-dominated counterpart. The plasma-generated fine
particles are negatively charged and suspended in the plasma.
The accumulation of fine particles causes low-frequency (about
10 Hz) spatiotemporal oscillation of the discharge. At high
pressure (>200 mTorr), the random fluctuations of the discharge
and the particle motions are suppressed. The Coulomb solids and
liquids are directly observed for the first time using an
optical microscope in the rf weakly ionized plasma. By properly
controlling the system parameters, 3-d hexagonal, face-centered
cubic (fcc), body-centered cubic (bcc) and hexagonal close-
packed (hcp) crystal structures and solids with coexisting
different crystal structures can be obtained. The defects and
the growth of the 3-d hexagonal crystal are also observed.
Increasing the rf power causes the transtion to the more
disorder liquid state and it exhibits a first-order phase
transition.
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