Enhanced light trapping and plasmonic properties of aluminum nanorods fabricated by glancing angle deposition

Vertically aligned arrays of aluminum (Al) nanorods were fabricated by glancing angle deposition (GLAD) method. Nanorods with maximum lengths of 200 and 350 nm were grown on 100 nm flat Al thin film. Total and diffuse reflectance profiles were measured using an ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer utilizing an integrating sphere to study detailed optical properties of Al nanorods in comparison to conventional planar Al thin film samples. Finite-difference-time-domain (FDTD) optical modeling method was utilized to simulate the optical response of Al nanorod array and thin film structures. FDTD simulations were carried out for periodic and random arrays of Al nanorods as well as for an isolated single nanorod in order to investigate effects of geometrical structure on plasmonic and light trapping effects. UV-Vis-NIR spectrum results reveal that total reflectance is inversely proportional with nanorod length, and decreases down to as low as similar to 25%-30% in the visible spectrum at wavelengths smaller than similar to 750 nm, while it stays at similar to 85%-90% for flat Al thin films at those wavelengths. FDTD simulation results indicate significant light absorption by GLAD Al nanorods mainly originating from enhanced light trapping and surface plasmon resonance among the nanorods. (C) 2015 American Vacuum Society.