Mechanical properties and stresses in thin gold films on a silicon substrate

摘要

Thin gold films with a thickness of 2μm were deposited on a silicon substrate by electron-beam evaporation. The material micro structure and internal stresses of the as-deposited gold films were characterized by scanning ion microscopy, orientation imaging microscopy, and X-ray diffraction. Microtensile tests of free-standing gold film samples were carried out to establish their intrinsic mechanical properties (in connection with a finite element analysis using crystal plasticity). Nanoindentation tests of the thin gold films attached to the silicon substrate were also carried out. Finite element analyses incorporating the crystal plasticity model were used to evaluate the effects of thin film textures, constraints due to the elastic substrate, and internal stresses on the plastic deformation behavior of the thin gold films under indentation at a direction normal to the film surfaces. Results of the combined experimental and numerical investigation indicate that the internal stresses have a strong effect on the uniaxial compression stress-strain behavior of the gold films and it may contribute to the relatively large hardness numbers obtained from the nanoindentation tests.