Measuring thin film and multilayer elastic constants by coupling in situ tensile testing with x-ray diffraction

Abstract

A direct determination of the Young's modulus and the Poisson's ratio in a 140 nm polycrystalline tungsten thin film deposited by ion-beam sputtering on a polyimide substrate has been performed by coupling x-ray diffraction measurements with in situ tensile testing. The method described in this letter to extract the Young's modulus of thin films from the evolution of the sin 2 ψ curves as a function of applied load only requires to know the substrate Young's modulus. The determination of the thin film Poisson's ratio can be realized without knowing any of the substrate elastic constants. In the case of the tungsten thin film, the obtained Young's modulus was close to the bulk material one whereas the Poisson's ratio was significantly larger than the bulk one.

Elastic Properties of Supported Polycrystalline Thin Films and Multilayers: an X-Ray Diffraction Study

“…Numerous experimental studies have evidenced a very probable softening of elastic constants in n anostructured materials, in particular the C 44 stiffness coefficient in multilayers with very low (Λ ≤ 3 nm) modulation wavelength [5][6][7]. In previous papers, we described an experimental technique combining in situ tensile testing and x-ray diffraction to extract the Poisson's ratio [8] and the Young's modulus of supported thin metallic films [9] and multilayers [10]. This diffractometric method differs from all the other mechanical, vibration, and acoustic techniques since it allows to measure average in-grain strains, and thus intragranular elastic constants.…”

Size effects on the Mechanical Behavior of Nanometric W/Cu Multilayers

“…A 200 N Deben™ mini-tensile testing device allows performing in situ tensile tests and can be equipped with several load cells (capacity from 5 N to 200 N) according to the chosen force range investigated [7].…”

“…Despite the number of studies devoted to length scale dependence of strength and deformation mechanisms in nanoscale multilayers [1][2][3][4][5][6], few of these focus on the mechanical response in the elastic domain. Elastic constants analysis in nano-crystalline metallic thin films and multilayers by means of a method combining X-ray diffraction and tensile testing has been a constant challenge in our laboratory for several years [7][8][9][10]. The present paper focuses on experiments involving stratified W/Cu samples with tungsten layer thicknesses ranging from 10.8 nm down to 1.5 nm and presenting constant average copper layer thickness of 0.2 nm.…”

An open-source platform to study uniaxial stress effects on nanoscale devices

“…[30][31][32] Electrical properties are easily accessed, and the applied stress can be determined using strain gauges or continuum-mechanics considerations on the bending geometry of the substrate. Silicon and III-V alloys, however, cannot accommodate large stress upon bending: cracks are created on the substrate surface and propagate, causing brittle failure of the substrate.…”