Plasma Physics and Chemistry for Nanomaterial and Device Fabrication

Abstract

This dissertation thesis revolves around one specific type of plasma: low pressure glow discharges. In the first half we will focus on particle dynamics visualized by laser light scattering in a silane-containing dusty plasma. A better understanding of par- ticle dynamics in dusty plasmas can be beneficial to both the intended synthesis of nanoparticles and the mitigation of nanoparticle contamination issues. Three distinct types of spatiotemporal behavior are observed for the dust particles, depending on the specific plasma power and pressure. The changing balance between the ion drag force and the electrostatic forces is hypothesized to be the dominant mechanism that determines particle dynamics in our case. It is also hypothesized that the dependence of particle dynamics on plasma power and pressure might be attributed to the generation and growth rate of dust particles. Based on our experimental results, the combination of laser light scattering and plasma emission proves to be an effective method for observing dust particles between tens of nanometers to a few hundreds of nanometers. In the second half we will instead focus on the application of a magneti- cally enhanced glow discharge, namely magnetron sputtering, as a critical de- position technique for the fabrication of anisotropic plasmonic nanostructures. Upon light irradiation at the resonance frequency, plasmonic nanostructures can exhibit interesting near-field enhancement and far-field extinction, arising from the resonant oscillation of conduction electrons in the nanostructures. Specifically, we fabricated plasmonic nanocups and nanorods from alternative low-cost materials such as copper, aluminum and titanium nitride, rather than from expensive noble metals such as gold and silver. The copper and alu- minum nanocups exhibit main plasmon resonances in the near-infrared region, potentially suitable for biological and window coating applications. The copper nanorods exhibit two plasmon resonance peaks as expected, corresponding to electron oscillations in the transverse and longitudinal directions, respectively. Two sputtering systems at the University of Minnesota Nano Fabrication Cen- ter (NFC) are used in this study. Due to certain limitations of the NFC systems we encountered during preliminary attempts at titanium nitride fabrication, we also constructed a custom-built angle sputtering system with a tiltable heated stage, introduced in detail in the appendix.