An analytical study of electrodiffusion (sweeping) of synthetic quartz crystals

The mechanism by which etch channels are reduced through electrodiffusion is discussed. To establish the relationship between the reduction in etch channel density and the electrodiffusion conditions, the latter were systematically altered. The diffusion of silver (Ag) into quartz crystals in an air atmosphere has the same etch channel-reducing effect as the diffusion of gold (Au). The total number of etch pits and etch channels was roughly identical with the number of line defects detectable by X-ray topography. There were no observable changes in the number of dislocations before and after electrodiffusion. The formation of etch channels is due to the occurrence of line defects with such a large strain energy that Ca⁺⁺ and Mg⁺⁺ impurity ions can be present. Electrodiffusion is effective in relieving this strain energy. When electrodiffusion takes place in an air atmosphere, the strain energy of the line defects is adequately relieved. The electrodiffusion experiments in air and in a vacuum using Au and Ag electrodes demonstrated that electrodiffusion prevents the diffusion of airborne impurities into the quartz crystal