Optimization of Ge/Si Core/Shell Nanoparticles Properties Through Nonthermal Plasma Synthesis

Core/Shell nanoparticles (CSNPs) are a type of nanomaterial that consists of two components: a core and outer shell composed of distinct materials. CSNPs are of interest due to their tunable optical properties and wide applicability in the biomedicine, semiconductor and catalyst fields. Nonthermal plasma approaches for synthesis of CSNPs have limited agglomeration while enabling crystalline growth at low reactor temperatures. Prior works have shown the capability to synthesize germanium-silicon CSNPs using nonthermal plasmas [1]. To optimize CSNPs production better control is needed over size uniformity, core and shell purity and dimension variation that may occur under diverse operating conditions. In this paper, we discuss results from computational investigations of the consequences of plasma operating parameters on the core/shell purity and thickness ratio of Si/Ge CSNPs. The test system is an inductively coupled plasma (ICP) having two plasma sources intended to separate core and shell synthesis zones for better core/shell purity and dimensional control. The computational platform is the Hybrid Plasma Equipment Model (HPEM) coupled with Dust Transport Simulation Module (DTS). CSNPs are produced under operating conditions of a few Torr, 10 W of ICP power, with Ar/GeH₄ and Ar/SiH­₄ gas mixtures flowing from top and middle inlets. The consequences of gas flow rate, inlet growth species fraction, and coil power on CSNP properties will be discussed.

[1] K. I. Hunter, et al. ACS Applied Materials & Interfaces, 9, 8263 (2017).