Nanostructured metal oxide films formed using microplasma-assisted, reactive chemical vapor deposition

Michael J. Gordon, PhD, University of California (Santa Barbara) is investigating plasma-based routes for direct synthesis of nanoparticles and hierarchically-ordered/structured thin films and nanostructures which have useful optical, electronic, and catalytic properties. In particular, we have developed a hydrodynamically-stabilized, microplasma jet-based growth technique to realize a variety of metal oxide nanowires (e.g., CuO, PdO, NiO, Fe₂O₃, SnO₂) on different substrates (e.g., Si and ITO) at high pressures (10-100 torr). See Fig. 3. Although many examples of nanowire growth using the vapor-liquid-solid (VLS) method with a catalyst particle exist, our work demonstrates that anisotropic growth can be realized without a catalyst, mask, or surfactant using microplasmas to create a directed, tunable flux of atoms, metastables, and clusters (i.e., by controlling ballistic vs. diffusional aggregation phenomena) for anisotropic growth. Variants of the microplasma technique are currently being used to synthesize porous and textured metal and alloy films as well as nano- and microstructured oxides for electrocatalysis, gas sensing, and solar cells.

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