Nonthermal Plasma Synthesis and Plasmonic Properties of Doped Silicon and Titanium Nitride Nanocrystal

This work examines the nonthermal plasma synthesis of phosphorus and boron doped silicon and titanium nitride nanocrystals. The localized surface plasmon resonance (LSPR) of these materials was investigated. Titanium nitride has a plasmon resonance in the visible and near infrared, like gold nanorods, making it a viable alternative to gold for biological applications like photothermal therapy treatments. Titanium nitride is less expensive and more temperature stable than gold as well as biocompatible. The nonthermal plasma synthesis route is a continuous production method that eliminates the need for long processing and morphology modification steps required for gold nanorod production. The plasmon resonance, composition, and particle uniformity of the titanium nitride was found to be very dependent on the flow rate of ammonia during synthesis. Doped silicon has a plasmon resonance further into the infrared region and a tunable absorption controlled by the substitutional doping concentration in the nanocrystals. The presence of the plasmon absorption was used as a diagnostic tool to understand dopant behavior in doped silicon. The plasmon behavior supports the hypothesis of a uniform doping profile for phosphorus dopants and surface doping profile for boron dopants in silicon nanocrystals.