Synthesis and oxidation of luminescent silicon nanocrystals from silicon tetrachloride by very high frequency nonthermal plasma

Abstract

Silicon nanocrystals have recently attracted significant attention for applications in electronics, optoelectronics, and biological imaging due to their size-dependent optical and electronic properties. Here a method for synthesizing luminescent silicon nanocrystals from silicon tetrachloride with a nonthermal plasma is described. Silicon nanocrystals with mean diameters of 3-15 nm are synthesized and have a narrow size distribution with the standard deviation being less than 20% of the mean size. Control over crystallinity is achieved for plasma pressures of 1-12 Torr and hydrogen gas concentrations of 5-70% through adjustment of the plasma power. The size of nanocrystals, and resulting optical properties, is mainly dependent on the gas residence time in the plasma region. Additionally the surface of the nanocrystals is covered by both hydrogen and chlorine. Oxidation of the nanocrystals, which is found to follow the Cabrera-Mott mechanism under ambient conditions, is significantly faster than hydrogen terminated silicon due to partial termination of the nanocrystal surface by chlorine.

A review of plasma–liquid interactions for nanomaterial synthesis

“…In addition, the IL is possible to be used as a flexible substrate for synthesizing SiQDs in low-pressure plasma, since the Si sputtering [269,270], and the decomposition of Si-containing gas or liquid precursors [271][272][273][274][275][276] are feasible.…”

Direct characterization of nanocrystal size distribution using Raman spectroscopy

“…(8) for size determination. In most cases, 2.0 nm is the critical limit for a silicon cluster to be considered as a stable nanocrystal-especially for the gas phase synthesis methods 11,[44][45][46][47] -and synthesis of silicon nanocrystals (either monodisperse or dispersed) smaller than 2.0 nm is unlikely. For this reason, exploiting Eq.…”

Research Update: Phonon engineering of nanocrystalline silicon thermoelectrics

“…To limit the average grain size to a few tens of nanometers after grain growth, we have chosen Si nanoparticles with diameter of about 6 nm produced by plasma CVD (PECVD) method. 74,75 Use of PECVD nanoparticles has a merit in obtaining a narrow size distribution. In addition, by terminating the Si nanoparticle surface with chlorine atoms and gradually oxidizing the surface (substituting the chlorine atoms with oxygen atoms) by exposing them in air, the oxide-shell thickness can be controlled through the exposure time.…”