Effect of annealing on the size dependent deformation behavior of thin cobalt films on flexible substrates

THIN SOLID FILMS

卷:624

Article

Marx, V. M.¹  Cordill, M. J.²  Toebbens, D. M.³  Kirchlechner, C.^1,4  Dehm, G.¹ 

[1] Max Planck Inst Eisenforsch GmbH, Max Planck Str 1, D-40237 Dusseldorf, Germany

[2] Austrian Acad Sci, Erich Schmid Inst Mat Sci, Jahnstr 12, A-8700 Leoben, Austria

[3] Helmholtz Zentrum Berlin Mat & Energie, Albert Einstein Str 15, D-12489 Berlin, Germany

[4] Univ Leoben, Dept Mat Phys, Jahnstr 12, A-8700 Leoben, Austria

关键词: Thin films;    Synchrotron diffraction;    Tensile testing;   

DOI  :  10.1016/j.tsf.2017.01.011

来源: Elsevier

【 摘 要 】

The effect of film thickness as well as the influence of heat treatment on the deformation behavior of thin cobalt films (50-2000 nm) on polyimide substrates was investigated using various tensile tests. Straining under an optical light microscope provides information about the fracture strain and cracking behavior. The annealed films exhibit enhanced crack onset strains between 4 and 7% compared to the as-deposited films with fracture strains of 1-2%. This is partly achieved by a mechanically induced martensitic phase transformation of cobalt from the face-centered cubic (FCC) to the hexagonal-closed packed (HCP) phase. Thereby, it was shown that the heat treatment can be used to increase the amount of metastable FCC phase. Complementary synchrotron diffraction experiments were used to determine the lattice strains which initially increase during straining. After reaching a maximum, the lattice strains decrease in the case of the as-deposited films due to crack formation and in the case of the annealed films due the strain-induced phase transformation and localized plastic deformation in the form of necks. At higher engineering strains, the formation of cracks is also observed in the heat treated samples. Additionally, a decrease of the maximum lattice strain could be found for the HCP phase below a film thickness of 200 nm and grain size of 50 nm in the as-deposited films which is caused by cracking. (C) 2017 Elsevier B.V. All rights reserved.

【 授权许可】

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