Study on the doping effect of spin coated Al and In doped and (Al/In) co-doped ZnO thin films for near-infrared plasmonic applications

摘要

Al and In doped and (Al/In) co-doped ZnO films were fabricated by spin coating for near infrared plasmonic applications. The total dopant concentration was fixed at 3 at.%, in which In and Al were varied sequentially. The as-coated films were annealed in air at 400 degrees C followed by second annealing at 300 degrees C in reduced atmosphere. Films selected with respect to carrier concentration (n) were further investigated for plasmonic applications. Films with a particular ratio of Al and In only exhibited n similar to 10 (20)/cm(3), necessary for plasmonic behaviour in near infrared. Structural studies were carried out by X-Ray diffractometer and band gap variations by calculating Urbach energy. Plasma frequency calculated from reflectance-transmittance spectra was theoretically verified using Drude-Lorentz equation. Al and In doped films and Al:In = 3:7 film exhibited metallic behaviour near to the wavelength 2000 nm. The films possessed minimum loss compared to those prepared by vacuum techniques. The properties obtained confirmed suitability of the films for plasmonic applications in the near infrared.