Unravelling the development of preferred crystallographic orientation in dual-phase amorphous/nanocrystalline Zr-V thin films

Abstract

Dual-phase amorphous/nanocrystalline alloys have been proven to present enhanced properties compared to their amorphous or nanocrystalline single-phase counterparts. These dual-phase materials are typically composed of nanocrystalline cores embedded in an amorphous matrix. In contrast, a new kind of dual-phase metallic films has recently been reported in which cone-shaped crystalline regions evolve as a result of competitive growth between the amorphous and crystalline phases with increasing film thickness. Here, we demonstrate that, unlike typical dual-phase alloys, Zr-V thin films exhibiting crystalline/amorphous competitive growth develop a preferred crystallographic orientation upon growth. Relying on pole figure observations, we uncover the development of a preferred orientation of the (110) crystallographic planes in the growth direction of the film with increasing film thickness. High-resolution transmission electron microscopy analysis reveals that the crystalline regions are formed by nano-branches which grow (110)-oriented. Based on this result, together with scanning and transmission electron microscopy observations, we associate the development of the thickness-dependent preferred orientation to the impingement between cone-shaped crystalline regions. This process triggers a selective growth mechanism that favors the selection of nano-branches growing near the direction of film growth. Our results and analyses provide a step forward in understanding the growth kinetics of dual-phase alloys presenting complex microstructures.