Nonthermal Plasma Synthesis of Silicon-Based Materials

Abstract

Nonthermal plasmas are finding increasing attention for the bottom-up synthesis of thin films, nanostructures, and nanoparticles that are difficult or impossible to produce with other fabrication techniques. The unique nonequilibrium environment provided in plasmas bypasses the thermodynamic constraints seen in other bottom-up approaches. Using a plasma-enhanced chemical vapor deposition (PECVD) process we synthesize thin films of hydrogenated amorphous silicon and silicon-germanium. The amorphous films then undergo a solid phase crystallization process to transform into a polycrystalline phase. The structural and transport properties of the films in both the amorphous and polycrystalline forms are studied and optimized for thermoelectric applications. We also utilize a nonthermal flowing plasma to produce highly monodisperse crystalline silicon particles. We present experimental evidence that during their growth in the plasma, particles become temporarily confined in an electrostatic trap until they grow to a critical size. Using this trapping mechanism, particles with controlled mean diameters between 60 to 214 nm are obtained. The results of this study contribute to our understanding of the mechanisms involved in the synthesis of silicon-based materials using nonthermal plasmas and provide a framework for designing more complex material systems.