Nucleation of silicon nanocrystals in a remote plasma without subsequent coagulation

Abstract

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Gas‐Phase Plasma Synthesis of Free‐Standing Silicon Nanoparticles for Future Energy Applications

“…Especially on size distribution analysis, we have shown that, Raman spectroscopy is non‐destructive and time‐efficient, and gives reliable results as the analyses agree well with other size analysis techniques like TEM and PL. We indeed have shown that Raman spectroscopy helps us understand the growth mechanism and the formation region of Si‐NPs in plasmas by analyzing the size distribution of synthesized Si‐NPs with varying the plasma parameters …”

“…In both of the pathways, further growth occurs via addition of the reactive species in the plasma leading to the formation of stable and fully crystalline Si‐NPs. During the nucleation, the growth reactions and atomic hydrogen association reactions occurring on the surface of the nanoparticle sustain crystallinity of Si‐NPs as a result of the energy released from these chemical reactions . In a controlled study of time modulated SiH 4 injection in the millisecond range, we have observed that the increase in the local density of SiH 4 does not increase the size of Si‐NPs produced, but it rather increases the number density of Si‐NPs and reduces the average size of these crystalline nanoparticles.…”

“…In addition, the rapidly cooling gas temperature prevents nanoparticle growth via sintering/coalescence and forms soft agglomerates. These observations revealed that the growth mechanism of Si‐NPs in the ETP is dominated by nucleation and CVD growth on the nanoparticle surface, and coagulation is highly unlikely …”

“…Therefore, in the ETP, the mechanisms that lead to the growth of Si‐NPs are different. Si‐NP growth starts via dissociation of SiH 4 molecules with Ar + ions in a dissociative charge‐exchange reaction that results in the formation of SiH m + ions . The formed molecular ions can subsequently be involved in two different polymerization pathways, i.e., radical polymerization and ion polymerization.…”

Characterization of Nanocrystal Size Distribution using Raman Spectroscopy with a Multi-particle Phonon Confinement Model

“…18 If no stress is observed from XRD, direct analysis of size distribution can be performed from the asmeasured Raman spectrum. Since all the nanoparticles have stable structures, as observed previously, 14 the crystallinity is well established, and concerns related with poor crystalline structures are ruled out for the Raman analysis.…”