Elastic anisotropy of polycrystalline Au films: Modeling and respective contributions of X-ray diffraction, nanoindentation and Brillouin light scattering

Abstract

Elastic properties of non-textured and {1 1 1}-fiber-textured gold thin films were investigated experimentally by several complementary techniques, namely in situ tensile testing under X-ray diffraction (XRD), nanoindentation and Brillouin light scattering (BLS). Specimens were probed along different directions to reveal the strong effects of elastic anisotropy at the (local) grain and (global) film scales. XRD allows the investigation of both local and global anisotropies, while BLS and nanoindentation are limited to global analyses. A micromechanical model, based on the self-consistent scheme, and accounting for the actual microstructure of the films, is applied to interpret experimental data. Although different types of elastic constants can be determined with the used experimental techniques (static/dynamic, local/ global), a good agreement is obtained, showing that comparison of these techniques is feasible when carried out carefully. In particular, the use of a micromechanical model to estimate the effects of the local elastic anisotropy at the film scale is unavoidable. The presented results show that XRD, BLS and nanoindentation should capture anisotropic texture effects on elastic constants measurements for materials with a Zener anisotropy index larger than 2. Conversely, the actual texture of a given specimen should be taken into account for a proper analysis of elastic constants measurements using those three experimental techniques.

Morphological Characteristics of Au Films Deposited on Ti: A Combined SEM-AFM Study

“…In this sense, for example, metal films presenting anisotropic elastic properties can be exploited for the production of innovative microelectrochemical devices [46]. In these films the elastic properties have a tensorial character resulting in direction-dependent response of the microelectrochemical devices [46]. On the other hand, for example, metal films with direction-dependent optical properties found recent interesting applications in devices exploiting the birefringence and dichroism effects on the nanoscale [47].…”

“…On the contrary, the increase of the roughness can be obtained by reducing the film thickness. In this sense, for example, metal films presenting anisotropic elastic properties can be exploited for the production of innovative microelectrochemical devices [46]. In these films the elastic properties have a tensorial character resulting in direction-dependent response of the microelectrochemical devices [46].…”

“…of the Au film with minimized surface roughness [46,47], require thick Au film deposited in oblique deposition condition. On the contrary, the increase of the roughness can be obtained by reducing the film thickness.…”

Deformation modes of nanostructured thin film under controlled biaxial deformation

“…The origin of the compressive stress in tungsten thin films is due basically to deposition processing: ion beam sputtering induces high compressive stress state by atomic peening process [45][46][47]. Noticeably, the x-ray stress analysis in W phase is much simpler than general cases because W is a perfect isotropic material from the mechanical point of view [36,48].…”

“…Different mechanical methods have been used to investigate the strength of metal thin films such as tensile testing, indentation and bending technique [31][32][33][34][35][36][37]. However, these tests still do not necessarily reflect the real conditions of systems in use.…”