Plasma Based Methods For The Synthesis And Deposition Of Nanoparticles

Nanoparticles exhibit tunable properties that offer the opportunity to improve existing technologies. Nanoparticles also possess emergent properties that are not shared by their bulk scale counterparts; this difference in properties allows for application of materials in devices and processes that were traditionally unsuitable. For semiconducting nanoparticles, the emergent and tunable properties hold promise for applications in solar cells, light emitting devices, sensors, catalysis, and a variety of other spaces. Explored first was the synthesis of InN, GaN, and InxGa1-xN at low pressure. These materials possess properties suitable for high-power and high-frequency electronics applications. The materials also possess bandgaps that span from the IR to the UV allowing for the use in a host of optoelectronic applications. A low-pressure RF plasma reactor was used to dissociate precursor gases whose subsequent reactions formed the nanoparticles. Nanoparticles were then collected and characterized with a host of techniques. Experiments were conducted that demonstrated the synthesis of crystalline nanoparticles with narrow size distributions. It was shown that particle size and crystallinity could be controlled through modulation of residence time and RF power respectively. This method demonstrated the synthesis of luminescent InGaN nanoparticles without any subsequent surface modification or post-synthesis treatment. To eliminate the time and capital costs of vacuum equipment and processes an atmospheric pressure microplasma operated with ambient surroundings was investigated. With this method crystalline silicon nanoparticles were synthesized. OES and FTIR were used in conjunction to ascertain if particles were synthesized in an oxygen contaminated environment. Results of the experiments indicate that particles were not exposed to oxygen in the reaction volume. Lastly an integrated atmospheric pressure synthesis reactor and aerosol jet printing process are described. Such a process would be useful for fabrication or prototyping of devices that require nanoaprticles. Combination of the reactor with a motorized stage and gantry allowed for deposition of nanoparticles with linewidths down to 100 microns. Methods to improve impaction efficiency were implemented and allowed for capture of sub-5 nm particles that exhibited luminescence at 680 nm. Also demonstrated was the control of synthesis parameters at the time of deposition to deposit particles with spatially varied properties.