2, University of Cunneticut, Stores, Connecticut, United States
Zinc Oxide (ZnO) nanocolumns (NCs) are promising building blocks for many existing and emerging applications owing to their unique optical, electrical, and piezoelectric properties. Specifically, the ZnO NCs could be used as seed layer for the growth of other oxide materials. Nanocolumnar ZnO is generally grown in randomly distributed arrays, in which the entire substrate is covered and only through lithographic methods is selectivity of growth location achieved. We propose a method to be able to grow ZnO NCs in hexagonally closed packed structure for spatially ordered seeding applications. Langmuir-Blodgett was used to construct a self-assembled monolayer of Silica Nanospheres (SNSs), 3.5 μm, 1.18 μm, 850nm, 500nm and 250nm in diameter, on silicon substrates. Z-axis oriented ZnO NCs were grown on top of the spheres using the glancing angle pulsed laser deposition (GAPLD) technique. ZnO columnar arrays grown in smaller SNSs diameter were observed to be vertical and at smaller sphere sizes, the colmuns were observed to form a hcp structure on top of each sphere grew in an hcp structure on top of each sphere. Columnar aspect ratios were found to be dependent on underlying sphere size as was c-axis crystallinity, with columns grown on 250nm SNSs showing considerable preffered orientation towards the (002). Columnar density per unit of coverage area was found to also be depend on underlying sphere size.