Structure of nanometersized silicon particles prepared by various gas phase processes

Abstract

We have explored various gas phase processes for the fabrication of nanometersized Si and SiO x particles and measured their structural properties (agglomeration, size, shape, crystallinity, surface roughness and internal structure) by conventional and high resolution electron microscopy. Agglomerated amorphous Si particles, 10±30 nm in size, were prepared by gas phase reactions including cluster growth processes in a low pressure silane plasma. Annealing at 900°C resulted in almost complete crystallisation of nearly spherical particles covered by an amorphous oxide shell. Inert gas arc evaporation of silicon yielded single crystalline, spherical Si particles, 4±16 nm in size, in which no defects were detected. 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 agglomerated, nearly spherical amorphous SiO x particles, 8±24 nm in size, with considerable surface roughness. Upon annealing at 900°C, the formation of 3±6 nm sized Si crystallites in the interior of these particles was observed. Ó

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

“…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].…”

Formation of SiO and Related Si-Based Materials Through Carbothermic Reduction of Silica-Containing Slag

“…On the other hand, formation of SiC according to the reactions (2) and (4) is unfavored for the process because the SiC formation occurs with consumption of SiO 2 or SiO.…”

“…7 can be explained as follows. At the very first stage, the vigorous emission of CO occurs because SiO 2 of the melt reacts directly with carbon on the still-fresh surfaces of graphite particles or crucible according to reactions (1) and (2). This results in converting the carbon surfaces to SiC.…”

Characterization of Deposited Nanocrystalline Silicon by Spectroscopic Ellipsometry

“…Many techniques including Chemical Vapor Deposition are used for nanostructure manufacturing, see e.g. [3]. The effect of the deposition parameters on nanostructure size and density are investigated [4,5] using highly reliable techniques for the sample observation such as Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) [6].…”