Optical properties and oxidation of -phase Ag-Al thin films

• Published in: Nanotechnology Vol. 28; no. 9
• Main Authors: De Silva, Kaludewa S B, Keast, Vicki J, Gentle, Angus, Cortie, Michael B
• Format: Journal Article
• Language: English
• Published: IOP Publishing 26.01.2017
• Subjects: intergranular oxidation; optical properties; plasmonics; silver alloys; thin films
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/1361-6528/aa5782

We investigate a series of Ag-Al thin films containing up to 12 at% Al with the purpose of discovering whether these alloys would be a better choice for nanophotonic applications than pure Ag. Variable angle spectroscopic ellipsometry, AFM, x-ray diffraction and density functional theory are applied to explore and characterize the materials. Electromagnetic simulations of optical properties are used to place the results into a theoretical framework. We find that the increase in electron-to-atom ratio associated with the Al additions changes the optical properties: additions of the order of 1-2 at% Al are beneficial as they are associated with favorable changes in the dielectric function, but for greater additions of Al there is a flattening of the absorption edge and an increase in optical loss. In addition, contents of more than about 2 at% Al are associated with the onset of time-dependent intergranular oxidation, which causes a pronounced dip in the reflectance spectrum at about 2.3-2.4 eV (∼500-540 nm).