Hot Wire and Spark Pyrolysis as Simple New Routes to Silicon Nanoparticle Synthesis

Abstract

Monocrystalline silicon nanoparticles with a mean diameter of between 30 and 40 nm have been synthesised by hot wire thermal catalytic and spark pyrolysis at a pressure of 40 and 80 mbar respectively. For the production a mixture of the precursor gases, silane and diborane or silane and phosphine were used. While hot wire pyrolysis always results in multifaceted particles, those produced by spark pyrolysis are spherical. Electrical resistance measurements of compressed powders showed that boron doped silicon powders have a much higher conductivity than those doped with phosphorus. TEM and XPS analysis reveals that the difference in electrical resistivity between boron an phosphorus doped particles can be attributed to phosphorus dopants being located at the surface of the particles where an oxide layer is also observed. In contrast, boron doped particles are far less oxidised and the dopant atoms can be found in the core of the particle. The results demonstrate that hot wire and spark pyrolysis offer a new simple route to the production of monocrystalline doped silicon nanoparticles suitable for printed electrical devices.

Synthesis and Properties of Plasmonic Boron‐Hyperdoped Silicon Nanoparticles

“…Boron doping modulates electronic, optical, and structural properties of silicon by modifying its charge carrier concentration. Boron‐doped silicon has been synthesized by solid, liquid, and gas phase methods in the form of bulk material, thin films, nanowires, and freestanding nanoparticles . Mechanisms of boron doping change with temperature.…”

“…Another interesting observation in the literature is that the boron doping is substitutional and does not change the diamond cubic crystal structure of silicon . This conclusion was mainly based on qualitative analyses of laboratory based powder X‐ray diffraction (XRD) and selected area electron diffraction (SAED) patterns.…”

“…Another interesting observation in the literature is that the boron doping is substitutional and does not change the diamond cubic crystal structure of silicon. [15,17,18] This conclusion was mainly based on qualitative analyses of laboratory based powder X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns. Structural analysis of nanomaterials with broad diffuse diffraction profiles using traditional crystallographic methods (i.e., Rietveld refinement) is compromised by issues such as signal-to-noise and degeneracy of structural models.…”

“…gas phase methods in the form of bulk material, [5] thin films, [6][7][8][9] nanowires, [10][11][12][13] and freestanding nanoparticles. [14][15][16][17][18] Mechanisms of boron doping change with temperature. At relatively low temperatures or short reaction times, doping is governed by kinetics, and at higher temperatures and sufficiently long reaction times, it is governed by the thermodynamic equilibrium solubility limit.…”