Time-dependent deformation of Sn micropillars

• Creep tests were performed on Sn micropillars of different sizes that indicated size-independent creep deformation.
• Creep stress exponent was evaluated to be ~ 1 which is indicative of diffusion creep.
• In-situ SEM tests under e-beam irradiation was confirmed that lattice diffusion governs creep of Sn pillars, differed from dislocation climb-based creep in bulk Sn.

In this study, time-dependent plastic deformation of micropillars fabricated from low melting point metal Sn (~ 505 K) was investigated at room temperature. Size-dependent strength was first evaluated and creep tests were then performed on the micropillars having diameters of 1 and 5 μm. Sn pillars showed significant creep deformation, and creep rate was independent of pillar size. Creep stress exponent was determined to be ~ 1, and negligible effect of e-beam irradiation on creep rate confirmed that the lattice diffusion must be the predominant creep mechanism. Creep deformation of Sn micropillars, therefore, differs from the dislocation-climb based creep in bulk Sn.

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