UC Santa Barbara

The ability to synthesize a wide range of nanostructured materials, as well as integrate them into larger systems, is fundamental to the development of next-generation micro- and optoelectronic devices, sensors, and energy harvesting and storage technologies. Toward this goal, we have developed a versatile, plasma spray-like deposition technique, based on flow-through microhollow cathode discharges (MHCDs) at 10-100 Torr. These microplasma jet sources can deposit nanoparticles, dense layers, and structured thin films of crystalline materials on virtually any surface (e.g., conductors, insulators, polymers, fibers, and lithographic patterns). Supersonic microplasma jets are seeded with organometallic precursors under oxidizing conditions to create a directed flux of growth species (e.g., atoms, ions, clusters, and/or nanoparticles) that are subsequently ‘spray-deposited’ onto the surface of interest at room temperature. A diverse range of nanostructured transition metal oxide materials, e.g., CuO, MnO2, RuO2, NiO, Fe2O3, CoxOy, and spinels (NiCo2O4) can be realized with the technique. These films were then used for electrochemical energy storage applications and are discussed with emphasis on the fabrication of microscale energy storage devices. We also highlight detailed measurements of Trot, Tvib, Te, and ne on various jets made using trace gas optical emission spectroscopy (OES) and Langmuir probe studies.