Large Area Plan-View Transmission Electron Microscopy Sample Preparation for Direct-Bonded Interfaces
We established that the preferential growth of a particular grain across Au-Au bond interfaces is enabled through an epitaxial transformation. Au (111) grains on one side of the interface grew into the other side – albeit with nanovoids remaining at the original interface. The microstructure of the transformed side consisted initially of nanotwinned, columnar Au while the grains that extended across the interface were initially randomly oriented under thermocompression bonding conditions. High resolution transmission electron microscopy measurements addressed the orientation dependence of the growing grains. This indicates that microstructure control in metal-metal bond pairs can impact the resultant grain structure and hence other properties.