High-Yield Core Luminescent Silicon-Carbide Nanocrystals from Mixed Liquid Precursors

North Dakota State University Fargo, Fargo ND

Investigators

Abstract

This project focuses on research investigates manufacturing challenges associated with the synthesis and processing of state-of-the-art fluorescent silicon carbide (SiC) quantum dots, from precursor to final product. Quantum dots are of commercial interest because of their ability to emit bright light of tunable color under steady excitation, a trait that recently won these materials a Nobel Prize in chemistry. However, bright fluorescence at the blue-to-green end of the visible spectrum is particularly challenging, especially without the use of toxic materials, such as lead. Proposed research will intend to enable the ‘bottom-up’ production of nontoxic nanocrystalline silicon carbide quantum dots of varied shape and size, with bright blue/green fluorescence for applications in displays, labels and sensors. In contrast to silicon, bandgap photoluminescence (PL) from SiC quantum dots has never been observed, with the reported PL reflecting impurities. The proposed research will attempt to resolve this issue to usher in a new era of quantum-confined nanocrystalline SiC materials, with broad relevance to defect tolerance and control in wide-bandgap semiconductors in general. The research resides on three successive tiers: precursor, processing, and surface treatment. Green purification schemes targeting the liquid precursor cyclohexasilane (CHS) will exploit its phase behavior to empower production at scale, where such precursors are safer than current standards like silane gas. At the processing level, intrinsic particle charge will be exploited for in situ field-flow fractionation, providing universal insight into the broad impact of surface charge on quantum yield. Finally, CHS/cyclohexane mixtures are ideal for SiC because of their matched stoichiometry, and plasma processing will enable the precise surface chemistry required for correct passivation. The insight gained from this research could lead to controlled size-tunable PL across the entire visible spectrum from nontoxic silicon-based materials, with bright blue/green emission from 2D and 3D nanoscale SiC. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.