Composition-driven transition from amorphous to crystalline films enables bottom-up design of functional surfaces

• Published in: Applied surface science 2021-02, Vol.538, p.148133, Article 148133
• Main Authors: Borroto, A., García-Wong, A.C., Bruyère, S., Migot, S., Pilloud, D., Pierson, J.F., Mücklich, F., Horwat, D.
• Format: Article
• Language: English
• Subjects: Amorphous metal alloys; Chemical Sciences; Growth kinetics; Material chemistry; Nanocrystalline alloys; Phase separation; Surface functionalization; Thin films
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.148133

[Display omitted] •A new growth mode in thin films is reported that enables manipulating functional properties.•Competitive growth between amorphous and crystalline phases is observed.•A kinetic model of the process is developed.•Optical reflectance components can be controlled to a large extent via manipulation of the surface morphology. Composition-driven transition to the crystalline state is characteristic of amorphous metal alloys and is widely observed in thin film. However, the transition zone (compositional range between single-phase amorphous and crystalline films) remains unexplored. Here, we demonstrate that this transition offers an excellent scenario for the fabrication of hybrid crystalline-amorphous architectures. The peculiar morphology of these nano(micro)-structured films provides a simple bottom-up route, applicable to a broad range of alloys, for obtaining adjustable multifunctional surfaces. In particular, we prove the feasibility of this approach as a one-step process for a precise control of specular and diffuse reflectance over the visible spectrum. Further, the growth kinetics of the formed two-phase nanostructures is demonstrated equivalent to a 2-dimensional amorphous-to-crystalline phase transformation. Using Zr-W alloys as a model system, fundamental parameters of the growth process and the corresponding metastable thickness-composition phase diagram are extracted. It evidences that the two-phase nanostructures, despite occurring in a wide range of compositions, can be easily hidden experimentally by growth kinetics and nucleation delay. These results open a new avenue on the surface morphology and related functional properties control in thin films.