Abstract

In this chapter, we will explore the bottom-up growth of freestanding (unembedded) Si nanocrystals in the gas phase using plasmas. Si nanocrystals can be unique nanostructures due to the effect of quantum confinement operating in all three spatial dimensions (Efros and Rosen 2000). This three dimensional (3D) quantum confinement affords the ability to modify the accessible energy levels within the material, leading to size-dependent optical and electronic properties (Brus 1986). Additionally, as the surface area to volume ratio increases with reduced nanocrystal size, the surface plays an increasingly important role for small, freestanding crystallites. This allows for the use of surface and strain engineering as additional parameters to tune material properties to a greater extent than is accessible in bulk materials or even in 1- or 2-D nanostructures. Freestanding Si nanocrystals are forward compatible with bottom-up manufacturing, such as self-assembly and 3-D printing, which adds new degrees of freedom in materials and device design compared to traditional top-down processing. As we discuss in this chapter, plasmas provide a growth environment that is well-tailored to the processing of high-quality Si nanocrystals for optoelectronic applications.