The effects of solid solution and oxide dispersion alloying on the viscoelastic behavior of Au alloy thin films. (15th April 2019)

• Record Type: Journal Article
• Authors: Mongkolsuttirat, K.; Smyth, J.R.; McLean, M.; Brown, W.L.; Vinci, R.P.
• Is Part Of: Acta materialia. Volume 168(2019)
• Page Start: 275
• Page End: 286
• Publication Date: 2019-04-15
• Subjects: Microelectromechanical systems MEMS -- Stress relaxation -- Dislocations -- Gold thin films -- Bulge test; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2019.02.023
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: The effects of solid solution and oxide dispersion alloying on viscoelastic relaxation behavior of Au alloy films were investigated by using gas pressure bulge testing in the temperature range of 20–80 °C. Three sets of 500 nm thick films were fabricated for the study: nominally pure Au, Au-V solid solution alloys with V concentration ranging from 0.89 to 5.4 at% V, and a Au-V2 O5 nanoparticle dispersion alloy with a V concentration of 5.4 at%. The residual stress, unrelaxed plane strain modulus, and normalized time-dependent effective modulus were determined as a function of alloy type and temperature. Both alloying approaches resulted in a refined grain size that was thermally stable. As expected, the fractional modulus decay measured after 3 h was greater at higher temperatures for all cases. Solid solution strengthening and dispersion strengthening were both effective at reducing the 3-h modulus decay, and the Au-V2 O5 films showed the largest resistance to relaxation at all temperatures studied. Activation energy analysis reveals a value of approximately 0.11 eV, matching the Peierls barrier height, for pure Au and the two alloys. The results are consistent with a viscoelastic stress relaxation mechanism based on reversible dislocation bowing, weak solid solution hardening through elastic solute/dislocation interactions, and strong dislocation pinning associated with oxide nanoparticles. Graphical abstract: Image 1