High-densely packed and uniformly distributed molybdenum oxide nanorods have been grown onto glass substrates by RF magnetron sputtering and subsequent annealing in an oxygen atmosphere. A two-step growth mechanism (sputtering redeposition and enhanced rearrangement during annealing) for the formation of MoO3 nanorods has been proposed. The morphological, structural, optical and electrical properties of the nanorods have been investigated systematically using atomic force microscopy, scanning electron microscopy, x-ray diffraction, micro-Raman, UV–visible, photoluminescence (PL) spectroscopy and dc resistivity studies. The nanorods in the as-sputtered film and the film annealed at 473 K are amorphous in nature. However, the nanorods in the films annealed at 573 and 673 K exhibit the presence of monoclinic Mo8O23 and orthorhombic MoO3, respectively. Vibrational analysis of the molybdenum and oxygen atoms in the nanorods is carried out by micro-Raman spectra. The nanorods show room temperature PL in the UV–visible region. The PL emission is found to be strongly enhanced by post-deposition annealing. The low temperature resistivity measurement is done on the as-deposited film; the activation energy and polaron hopping energy for electrical conduction are calculated. The MoO3 nanorods are expected to exhibit enhanced functionality, particularly in nanoscale, photochromic and gas sensing applications.

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We studied localized surface plasmon resonances (LSPR) at different compositions, substrate temperatures, and mass thicknesses of Ag-Au alloy nanoparticle films grown by sequential pulsed laser deposition. The LSPRs were pronounced at all compositions of the films grown at high substrate temperature of about 300 °C as compared to those grown at room temperature. The alloy formation and composition of the films were determined using X-ray photoelectron and energy dispersive spectroscopy. Films' mass thickness and compositional uniformity along the thickness were determined using X-ray reflectometry and secondary ion mass spectroscopy. Atomic force microscopic analysis revealed the formation of densely packed nanoparticles of increasing size with the number of laser ablation pulses. The LSPR wavelength red shifted with increasing either Au percentage or film mass thickness and corresponding LSPR tuning was obtained in the range of 450 to 690 nm. The alloy dielectric functions obtained from three different models were compared and the optical responses of the nanoparticle films were calculated from modified Yamaguchi effective medium theory. The tuning of LSPR was found to be due to combined effect of change in intrinsic and extrinsic parameters mainly the composition, morphology, particle-particle, and particle-substrate interactions.

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