Plasma annealing: A route to precise controlled growth of MoO3 nanostructures

This paper discusses a novel technique for growth of molybdenum oxide nanostructures on common glass substrates with precise control over their number density, shape and dimension. The method involves thermal evaporation of MoO3 powder on two types of substrates; glass and nickel (Ni)-coated glass substrates, at room temperature. MoO3 deposited on each type of substrate was annealed in two different ambients; in air and oxygen plasma. Our experimental results revealed that by changing annealing duration only and keeping all other experimental conditions constant, nanostructures with well-defined size and shape were obtained only on Ni-coated glass substrates by annealing in air or oxygen. These experiments divulged that Ni-provided heterogeneous nucleation sites for formation of nuclei that further grew into nanostructures. The shape of nucleus during growth was determined by a combination of three factors; interfacial energies, elastic strain energies and minimization of surface energies, each active at different stages of growth.