Ternary SiGeSn Alloy Nanocrystals via Nonthermal Plasma Synthesis

We report on the synthesis of ternary SiGeSn nanocrystals (NCs) produced via nonthermal plasma synthesis from silane (SiH4), germane (GeH4), and tetramethylstannane (Sn(CH3)4) precursor sources. Detailed structural, chemical, and vibrational analyses show that all three elements are incorporated both on the NC surface and within the NC core. Incorporation of Sn into the NC core is realized using a secondary injection of SiH4 and GeH4 precursor gases in the after-glow region of the plasma, which kinetically traps Sn in the core. We demonstrate compositional tunability of the SiGeSn NCs in which the Si and Ge ratios can be varied broadly at low Sn concentrations. We also show tunability of the Sn content up to ~2 atomic percent as revealed by ICP-MS analysis. More generally, this report demonstrates how nonthermal plasma synthesis can be used to produce metastable ternary nanostructured alloys involving thermodynamically insoluble constituents.