The effect of orientation and pore size on nano mechanical behaviour of Ag thin films: a comparison between experiment and atomistic simulation

ABSTRACT

This paper describes the thickness-dependent texture evolution during annealing in Ag thin films, commonly used in micro and nano-devices. The effect of porosity and crystal orientation on mechanical properties for the films deposited by the magnetron sputtering method is particularly addressed using nano-indentation experiment and atomistic simulation. X-ray pole figure analysis revealed that the films exhibited sharp fibre texture with a major <1 1 1> component accompanied by minor twin components of <5 1 1> and <5 7 13> and a weak component of <1 0 0>. The mechanical behaviour of the films was investigated experimentally using a Berkovich tip to measure the hardness (H) and modulus of elasticity (E) at each individual grain and porous region. The average Young’s modulus of strongly oriented [1 1 1] grain at porous and non-porous regions is estimated to be 44 ± 7 and 67 ± 5 GPa. Molecular Dynamics simulations have been performed on (1 1 1), (1 1 0), (0 0 1), (5 1 1), and (5 7 13) surfaces of Ag single crystal using a spherical indenter to investigate the anisotropic nature of hardness and elastic modulus from the Load∼Indentation depth curves. The mechanical properties of [1 1 1] oriented single crystal in the presence of a sub-surface void have been studied. Our results have demonstrated that the void acts as an efficient absorber of dislocation limiting the extension of the plastic zone. The simulated modulus of elasticity (E: 54.2 GPa) results obtained at a temperature of 300 K in the presence of a void are compared with experimentally measured values with a variation of around 6%.

KEYWORDS:

• Nano-indentation
• molecular dynamics
• void
• yield load
• pop-in event
• fibre texture

Acknowledgements

The authors gratefully acknowledge Dr. Arup Dasgupta, Head PMD, Dr. S. Raju, Director, Metallurgy and Materials Group, and Dr. B Venkatraman, Director, IGCAR for their support and encouragement.

Disclosure statement

No potential conflict of interest was reported by the author(s).