Nonsinusoidal buckling of thin gold films on elastomeric substrates

Buckling of stiff thin films on compliant substrates represents a variety of applications, ranging from stretchable electronics to micro-nanometrology. Different but complementary to previously reported sinusoidal buckling waves, this letter presents a nonsinusoidal surface profile of buckled thin Au films on compliant substrates, specifically, a secondary dip on top of buckling wave or rather broadened wave top with very sharp trough. This nonsinusoidal profile is likely due to tension/compression asymmetry, i.e., different strengths in tension and compression resulted from the polycrystalline, grained microstructure of metal film. Finite element analysis with asymmetric tension/compression material model has reproduced the experiments well qualitatively.