Onset of Silicon Nanoparticle Crystallinity in Nonthermal Plasmas

Group IV nanoparticles (NPs) have a wide range of applications in the semiconductor, catalyst and biomedicine fields due to their favorable electrical and optical properties. Nonthermal plasma synthesis is an attractive method to control NP size uniformity and produce crystalline NPs that contain minimal charge carrier traps and defects. Prior experimental and computational works [1] propose that the crystallinity of NPs synthesized in plasmas is likely the result of stochastic particle heating by surface reactions.

This paper discusses results from computational investigations of heating and crystallization of NPs in inductively coupled plasmas (ICPs), capacitively coupled plasmas (CCPs) and pulsed plasmas. The Hybrid Plasma Equipment Model (HPEM) coupled with Dust Transport Simulator (DTS) allows for the temporal and spatial tracking of NP properties in nonthermal plasmas. The DTS has been improved to track the temperature of individual nanoparticles through ion and neutral particle interactions. The test system is a cylindrical CCP with a single plasma source that operates at a pressure of a few Torr, 10 W of CCP power and with Ar/SiH­₄ as the feed gas. The impact on the temperature-dependent crystallization of Si NPs of an expanded operational space (plasma type, power, pressure, mixture) and mechanisms of crystallization will be discussed.

[1] Kramer et al, J. Phys. D: Appl. Phys. 47, 075202 (2014).