Apparatus for producing silicon nanocrystals based on inductively coupled plasma.
Researchers at the Korea Institute of Energy Research have developed a new apparatus for producing silicon nanocrystals based on inductively coupled plasma. Silicon nanocrystals have been widely investigated for several years because of their many interesting properties and potential use in several applications. Recently, silicon nanocrystals have been used in solar cells and light emitting device (LEDs). Silicon is an environmentally friendly material and is utilised for various applications in the field of electronic materials. The field of silicon nanocrystal production has grown enormously of late, in response to the observation of quantum confinement in porous silicon. Silicon is already widely used in the semiconductor industry, in large part because of its nontoxic properties and abundance, being the second most abundant element in the earth’s crust. Due to the high capacity of silicon paired with its relatively environmentally friendly properties it is an ideal material for use as a replacement to more commonly used environmentally costly materials. The common process of producing silicon nanocrystals can be classified into three distinct areas: solid-state reaction, liquid state reaction, and vapour state reaction. The solid-state reaction is the process whereby a thin film of SiO2, Si3N4 or the like containing excess Silicon (Si) is formed and subjected to heat treatment to enable the condensation of silicon and subsequent formation of silicon nanocrystals in a SiO2, Si3N4 or SiC matrix. In the liquid state reaction, silicon nanocrystals are prepared via a chemical reaction of silicon compounds, this is done through the application of variant methods, for example the high-temperature supercritical method. In the vapour state reaction, silicon nanocrystals are prepared by passing a silane compound gas through a high energy region such as laser or plasma. In the case of all three traditional silicon nanocrystals reaction methods (solid, liquid and gas) the process incurs significant cost due to the substantial need for heat energy and expensive deposition equipment. What’s more, in the liquid State reaction issues arise due to the severe difficulty in controlling particle size, which in turn leads to poor crystallinity quality. The vapour state reaction incurs further issues due to the extreme use of energy resulting in aggregated nanocrystals and the formation of secondary particles. To overcome the inherent issues of solid, liquid and vapour silicon nanocrystal reactions non-thermal plasma, such as inductively coupled plasma (IPC) has begun to be used. However, the conventional ICP-based apparatus has limitations and can result in issues pertaining to the management of the particle size of silicon nanocrystals, as well as extending reaction time and deteriorating silicon nanocrystal quality. To combat the aforementioned limitations in silicon nanocrystal production a new apparatus method has been designed, which can minimise plasma diffusion inside the reactor during production using ICP to improve the particle size characteristics and quality of the silicon nanocrystals.