Synthesis and structural characterisation of Si and SiO_x particles of nanometer sizes

Abstract

The possibilities of various gas phase processes for fabrication of nanosized Si and SiOx particles have been explored in a comparative Study. Conventional and high resolution electron microscopy was used to investigate in detail agglomeration, size, shape, crystallinity, surface roughness and internal structure of the particles, respectively. Accretions of nearly spherical crystalline Si particles of 2‐8 nm size mostly embedded in amorphous matrix were prepared by means of a gas evaporation cluster source. Their structural characteristics depend on the aggregation conditions applied. Inert gas are evaporation of silicon yielded single crystalline, spherical Si particles 4‐16 nm in size being completely free of defects. These particles, agglomerated into chains and tangles, are covered entirely by a thin amorphous oxide layer. Thermal evaporation of solid SiO in an inert gas atmosphere produced highly agglomerated, nearly spherical amorphous SiOx, particles 8‐24 nm in size with a considerable surface roughness. Upon annealing at 900°C the formation of 3‐6 nm sized Si crystallites in the interiro of these particles were observed.

Lattice contraction in nanosized silicon particles produced by laser pyrolysis of silane

“…Different from other observations at Si-based particulates [8][9][10][11] no particle agglomeration was found which may be due to the rapid transfer of particles from the reaction zone into high vacuum, directly after formation. This 'dilution' procedure obviously prevents the formation of larger aggregates in the cluster beam.…”

“…Remarkably, they do not agglomerate into larger aggregates as it is known from other routes of synthesis [8][9][10][11]. Instead, the deposits consist of separated particles, covering at random the substrates used for collection and being stacked onto each other upon prolonged deposition.…”

“…Besides erosive surface techniques widely used to process bulk silicon [2,3], there is growing interest in gas phase synthesis of nanosized Si particles which, by embedding them in a passivating matrix, may be stabilised against influences of the ambient. Various methods of synthesis are reported ranging from co-sputtering of Si and silica, ion implantation of Si into silica, laser ablation and gas phase evaporation of silicon to plasmaassisted decomposition of silane [4][5][6][7][8][9][10]. New hints to the self-limiting nature of oxide formation at nanosized Si particles were obtained from Si particles produced by inert gas arc evaporation [11].…”