Growth and Mechanism of Network‐Like Branched Si₃N₄ Nanostructures

Abstract

The high‐yield synthesis of network‐like branched silicon nitride (Si3N4) nanostructures by a simple template catalyst‐assisted pyrolysis of a polymer precursor, perhydropolysilazane, was reported. The templates were silicon wafers deposited with Fe films of 5–20 nm in thickness. The processes simply involved thermal cross‐linking of the preceramic polymer, crushing of the solidified polymer chunks into fine powder, and thermal pyrolysis of the powder under flowing high‐purity nitrogen. The collected white network‐like branched nanostructures are α‐Si3N4 of hexagonal phase, and their microstructures, in which the diameters of each linear part of the network‐like nanostructure varied in a very wide range from tens of nanometers to hundreds of nanometers, strongly depend on the applied growth parameters, where the key factors are the heating rate and catalyst thickness for change in the diameters. It was proposed that the Si3N4 nanonetworks were formed through “metal‐absorption on the surface of nanostructures” model by vapor–liquid–solid mechanism. The reaction mechanism of Si3N4 nanonetworks was also discussed.

Growth of One‐Dimensional Nanostructures in Porous Polymer‐Derived Ceramics by Catalyst‐Assisted Pyrolysis. Part II: Cobalt Catalyst

“…It is known that the surface of these liquid droplets has a large accommodation coefficient, and therefore they are a preferred deposition site for the incoming SiO and CO gases, 24 which form during pyrolysis of the polysiloxane preceramic polymer, 35,40,55 and for nitrogen from the heating atmosphere. The incorporation of these gases may lead to a supersaturation of the liquid phase in the elements forming the crystals (SiC, Si 3 N 4 ) 56–59 . The presence of catalyst droplets at the tips of the Si 3 N 4 nanowires (Fig.…”

“…The incorporation of these gases may lead to a supersaturation of the liquid phase in the elements forming the crystals (SiC, Si 3 N 4 ). [56][57][58][59] The presence of catalyst droplets at the tips of the Si 3 N 4 nanowires ( Fig. 4(a)), together with the fact that nanowires were obtained only when Co was present, indicates that the growth proceeded through a solution precipitation (VLS) mechanism.…”

Nitrogen reaction with silicon: Investigation of Si undercooling and Si3N4 growth

“…Si 3 N 4 facetted dendrites have been described in the literature as the result of vapor phase growth [23,24]. As they appear only on the droplet surface, these facetted dendrites apparently grow after solidification, during the droplet cooling down, from gaseous N 2 and from Si vapor surrounding the droplet (the partial pressure of Si at the melting point is 10 À 6 atm).…”

“…EDS confirmed the presence of nitrogen; however Raman analysis did not permit us to define which polytype they are made from, because of high fluorescence emission. It has been reported that a-Si 3 N 4 is formed under such conditions [24]. …”

Fabrication and properties of ceramic 1D nanostructures from preceramic polymers: a review

“…76 In an another very recent study, 77 Si wafer was coated with 5-20 nm Fe film using a magnetron sputtering, the coated wafer was separated from a cured and crushed PHPSZ precursor which was put inside an alumina crucible, following by the pyrolysis at 1100-1400uC for 2 h in N 2 . After completion of the treatment, white products characterised as network-like branched Si 3 N 4 nanowires were collected on the surface of the Si wafer.…”