Nuclear Magnetic Resonance Spectroscopy of Silicon Nanoparticles

Abstract

Despite the widespread use of hydrofluoric acid (HF) in the preparation of silicon surfaces, the true nature of fluorinated surface species remains unclear. Here, an array of characterization techniques led by solid-state nuclear magnetic resonance spectroscopy is employed to uncover the nature of fluorinated moieties on the surface of hydride-terminated silicon nanoparticles. A structural model that explains the observed trends in 19F and 29Si magnetic shielding is proposed and further supported by quantum chemical computations. Fluorine is incorporated into local oxidation domains on the surface and clustered at the interface of the oxide and surrounding hydride-terminated surface. Silicon sites capped by a single fluorine are also identified by their distinct 19F and 29Si chemical shifts, providing insight into how fluorine termination influences the electronic structure. Finally, challenges associated with Teflon® contamination are highlighted that future explorations of nanomaterials may have to contend with.