Super structures of columnar thin films: Photonic properties and their applications

 Deposition of sculptured thin films by columnar growth during physical vapor deposition with an obliquely incident vapor flux on the substrate is well known. We have been investigating building superstructures at the micron and sub-micron lengthscales of these sculptured thin films. This results in a two scale problem: with porosity and columnar structure at the nanoscale and a carefully engineered morphology at the wavelength scale.  This can result in photonic structures with anisotropic or chiral building blocks. Periodically patterned columnar thin films can behave as a blazed diffraction grating with high transmission diffraction efficiencies even at UV wavelengths. Such structured films of silver show interesting uni-directional coupling to surface plasmons and also represent a unique system of anisotropic metal gratings. Another application is fingerprint visualization enhancement by deposition of columnar thin films and fluorescent dye treatment