Nanoindentation experiments were conducted for 30 nm-thick Au films on two types of substrates, polyimide (compliant) and glass (stiff), to clarify the dominant mechanics of incipient plasticity from the interface. A high resolved shear stress T(r) could be effectively applied to the Au/polyimide interface due to the compliant substrate, and plastic deformation was initiated at the interface. The critical resolved shear stress T(crss) at the interface was determined to have a value of 0.4 similar to 0.5 GPa. On the other hand, in Au/glass, T(r) peaked within the Au film, and the maximum values were 1.1 similar to 2.2 GPa depending on the tip radius, whereas the values of T(r) at the Au/glass interface were almost identical at 0.5 similar to 0.7 GPa. Therefore, plastic deformation might be initiated from the Au/glass interface. The values of T(crss), for heterogeneous nucleation at the interfaces were smaller than that for homogeneous nucleation in the Au films. (C) 2010 Elsevier B.V. All rights reserved.