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.

Elaboration of VO2 films with good thermochromic properties remains a challenge because it is mandatory to avoid other intermediate phases belonging to the vanadium-oxygen system. In this work, we propose vanadium nitride (VN) as a new precursor to obtain thermochromic VO2. VN films were reactively sputter-deposited on Si substrates by using an in-line semi-industrial machine. The films of 175 nm thickness were submitted to an annealing process implemented at different durations at 450°C. X-ray diffraction and Raman spectrometry were performed for structural characterizations of the oxidized films showing the presence of monoclinic VO2 in a wide range of oxidation time. As the annealing time increased, V2O5 appeared to affect the performance of the oxidized films. The TEM analysis carried out on the oxidized sample for 25 minutes showed that there is an abrupt interface between VN and VO2. The thermal-induced properties of the studied films were analyzed in terms of their electrical resistance employing a-2-four-point probe method and their emissivity modulation properties by infrared camera. The results showed a thermochromic behavior for the samples oxidized in the range of 15-35 min. On the contrary, the presence of residual VN layers in samples oxidized for less than 15 min and V2O5 in the ones annealed for more than 35 min hindered the thermochromic behavior of these films. Bringing together all the characterization techniques used a phase diagram of VN oxidation was plotted. The results of this work suggest that VN is an interesting new precursor to synthesize thermochromic VO2 films.

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