Widely tunable optical properties via oxygen manipulation in an amorphous alloy

The ability to widely tune the optical properties of amorphous alloys is highly desirable especially for their potential applications in optoelectronic devices. In this work, we demonstrate that introducing oxygen into an amorphous alloy system of Co-Fe-Ta-B enables the formation of various amorphous derivatives ranging from metals to semiconductors, and eventually to insulators. These oxygen-containing amorphous derivatives gradually become transparent with the opened bandgaps, leading to a continuous increase in their optical transmittance. Furthermore, the reflective metal-type amorphous alloy and transparent insulator-type amorphous oxide of the system can be integrated together to realize the full-color tuning over the entire visible spectral range. This provides a new way to develop large-area color coatings with high design flexibility and full-color tun-ability. We envisage that the design concept proposed in this work is also applicable to many other amorphous alloy systems, from which all types of amorphous materials including alloys, semiconductors and insulators may be developed to show unprecedented optical functionalities.