Formation of metal nanoparticles tailored by dynamic oblique deposition for plasmonic applications

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Using a dynamic oblique angle deposition technique, we demonstrate the direct formation of Ag and Au nanorods with quasi-parallel major axes on a template layer of oxide having a strongly anisotropic surface morphology. The optical properties of the nanorods are tuned by varying the deposition conditions without any pre- or posttreatment, and the resulting nanorod arrays exhibit high surface-enhanced Raman scattering (SERS) activity. In addition to high macroscopic uniformity over a large area, our nanorod arrays contain a high density of isolated minerals. Using the optimum Ag nanorod arrays, the SERS imaging of the microdroplets of a rhodamine 6G solution is successfully demonstrated The space resolution of the imaging is of the order of at least a few μm. These features are suitable for the SERS imaging of biomaterials. In addition, we demonstrate the growth of unusual metal whiskers by glancing angle deposition on a high temperature (HT-GLAD) substrate, while the usual columnar structures completely disappear due to accelerated surface diffusion. HT-GLAD is essential fur the nucleation of the whiskers and efficient supply of metal atoms on the side surface of the vertically growing whiskers. HT-GLAD will, for the first time, reveal the mechanisms fm the vapor growth of metal whiskers.