Optical and structural properties of quinoline metal chelate thin films deposited by glancing angle deposition

Highly porous organic nanostructured thin films of quinoline metal chelates have been fabricated using glancing angle deposition (GLAD). GLAD is a physical vapour deposition technique that enables precision nanostructured thin film features to be fabricated in a single step process. Quinoline GLAD films have demonstrated a notable absence of column broadening and a predominantly circular column cross-section, which is contrary to the secondary structural anisotropy commonly observed in inorganic GLAD films. These structural properties give rise to an optical anisotropy leading to negative values of in-plane birefringence that increases with deposition angle. The structure and optical anisotropy of the films were characterized using variable angle spectroscopic ellipsometry, Bruggeman effective medium approximations and scanning electron microscopy. Another unique feature of the organic films was the formation a solid wetting layer prior to nanostructure growth. The effects of substrate surface energy and vapor deposition rate on the initial wetting layer growth of porous columnar tris(8-hydroxyquinoline) aluminum (Alq3) nanostructures are described.