High-resolution imaging of Σ=5 tilt boundaries in gold

Abstract

Until recently most of the information concerning the atomic structure of grain boundaries in metals has been obtained using molecular static and molecular dynamic computational techniques. With the recent developments of intermediate voltage microscope (300-400KV) this situation has changed and grain boundary atomic resolution is now possible for most metals. The purpose of this research is to examine the atomic structure of Σ=5 tilt boundaries in Au by high resolution microscopy and to compare the results to computational models.Thin film Au bicrystals containing Σ=5 (θ=36.5°±0.5) tilt grain boundaries were produced by epitaxial growth on NaCl bicrystalline substrates using a technique described in detail elsewhere. All high resolution images were obtained with a Philips 430 ST microscope using axial illumination and without objective aperture. All image simulations were obtained using the multislice formalism with EMS programs. All four {200} reflections from each crystal were used for the simulations with the following instrumental parameters; accelerating voltage V=300KV, spherical aberration constant Cs=1.1mm, defocus spread Δ=8nm and semi-angle beam divergence α=8mrad.