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 ce ll (SDC). Voltamograms on single grains were obtained and show the shape wh ich is characteristic for a (111) single crystal plane. The potential depen dence of the capacity was recorded as well. The crystallographic orientatio n of each grain was determined by Laue X-ray back scattering. All grains ha ve a (111) orientation but different azimuth angles. This angle was determi ned quantitatively for different grains. SEM micrographs show that the brea dth of the grain boundaries is some 12 mu m. The terraces of the grain and the grain boundaries were investigated by scanning impedance measurements u sing the SDC. Three different droplet diameters (50, 100 and 250 mu m) were used. The grain boundary could be detected with all cells. The local capac ity within the grain boundary was determined from this experiment. It is fo und to be 60% higher than that of the grains themselves, probably due to th e enlarged area within the ditch. The structure of the specimen is discusse d and a model describing the results is presented. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.