Localised investigation of coarse grain gold with the scanning droplet cell and by the Laue method

A coarse grain gold specimen was investigated using the scanning droplet cell (SDC). Voltamograms on single grains were obtained and show the shape which is characteristic for a (111) single crystal plane. The potential dependence of the capacity was recorded as well. The crystallographic orientation of each grain was determined by Laue X-ray back scattering. All grains have a (111) orientation but different azimuth angles. This angle was determined quantitatively for different grains. SEM micrographs show that the breadth of the grain boundaries is some 12 µm. The terraces of the grain and the grain boundaries were investigated by scanning impedance measurements using the SDC. Three different droplet diameters (50, 100 and 250 µm) were used. The grain boundary could be detected with all cells. The local capacity within the grain boundary was determined from this experiment. It is found to be 60% higher than that of the grains themselves, probably due to the enlarged area within the ditch. The structure of the specimen is discussed and a model describing the results is presented.