Color tuning by local sputtering metal nanolayer on microstructured porous alumina

This article reports a novel color tuning method by local sputtering nanolayers on microstructured porous alumina (PA) templates with different pore depths. With the aid of scanning electron microscopy observation, physical models of the original and sputtered PA templates are set up, and the details of the color tuning method are further proposed. Two series of colors covering the whole visible range are first obtained by respectively sputtering Cr and Ag nanolayers on two groups of PA templates with pore-depths ranging from 230 to 490 nm. A vivid colorful pattern of "Butterfly wings" is then prepared by local sputtering such Cr and Ag nanolayers on the surface of a PA with 310 nm pore-depth. The scanning electron microscopy images of Cr and Ag sputtered PA surfaces show different microstructures, which is in agreement with different color exhibiting. This method is expected to have a potential of being widely applied in the fields of micro-optics, microstructures, advanced materials, and micro/nanotechnology.