Invited: Microplasma Spray Deposition of Nanostructured Films for Catalytic, Magnetic, and Photonic Applications

We present a hybrid plasma spray deposition technique, based on geometrically-confined, supersonic microplasma jets, which can realize a wide range of metal oxide/sulfide nanoparticles and nanostructured thin film materials (e.g., CuO/CuS, ZnO, SnO₂, NiO/NiFe₂O₄) on virtually any surface. Organometallic precursors are dissociated in a hollow cathode microplasma jet under different reducing/oxidizing atmospheres at high pressure (10-100 torr), creating a directed flux of active metal and oxide species for the subsequent growth of nanostructured films. Interaction of the jet afterglow with the background gas can create additional species (e.g., excited neutrals, radicals, etc.) which participate in film growth. By varying supersonic jet flow characteristics, plasma current, precursor flux, source distance, and deposition time, deposits ranging from isolated nanoparticles to films of fibers, aggregates, nanowires, and dense columns can be realized. The talk will highlight our recent efforts [1-5] in oxide/sulfide nanomaterial synthesis via microplasmas with emphasis on the physics of the jet source, dynamics of the growth process, and applications such as solar cell electrodes, photo(electro)catalysis, and nanogranular films for magnetic exchange bias applications.

[1] T. Koh and M.J Gordon, J. Phys. D: App. Phys. 46, 495204 (2013).

[2] T. Koh, I. Chiles, and M.J Gordon, Appl. Phys. Lett. 103, 163115 (2013).

[3] T. Koh and M.J Gordon, JVST A 31, 061312 (2013).

[4] T. Koh and M.J. Gordon, J. Crystal Growth 363, 69 (2012).

[5] T. Koh, E. O'Hara, and M.J. Gordon, Nanotechnology 23, 425603 (2012).