Grain boundary contributions to transport

Several important features of grain boundaries, as related to thin metallic film properties, will be discussed. Boundaries are particularly important in films where diffusional processes occur mainly at low temperatures and grain sizes are of the order of 1μm or less. One phenomenon of interest is electromigration where a high dc current density causes a net atom drift in the direction of electron flow, mainly along boundaries. Non-uniformities in the boundary network lead to a divergence in the diffusion flux, with resultant mass depletion and void formation. A related discussion will be presented on radioactive tracer self-diffusion in gold films at temperatures below 200°C where dislocations and grain boundaries are controlling. Relationships to electromigration will be illustrated. Also to be discussed will be measurements of grain boundary contributions to electrical resistivity in terms of specific grain boundary models. Analytical expressions will be presented to allow extraction of the boundary contributions. © 1972.