It was observed that Ag ions moved from the anode to cathode with higher mobility than those of Au and that the residual Ag was closely corresponded to the substitutional alminum impurity. The entire Ag is used up on alminum for charge compensation to form the association A1-Ag'. The diffusion of Ag in an air atomosphere has the same etch channel reducing effect as the diffusion of Au.The line defects observed by X-ray topography before and after sweeping were not changed by sweeping under any conditions. It was confirmed the total number of etch pits and channels roughly the same as a number of line defects detected by X-ray topography and that electrodiffusion. though it reduced the etch channel density. did not change the total number of line defects.In comparing the results of impurity analysis of the samples before and after electrodiffusion. it was seen that Na+ and Li' were easily diffused to the outer surface of the crystal. while the concentrations of A13', K'. Ca'+. and M g + + were not changed. The impurity analysis of the unswept samples showed that Ca" and Mg" significantly decreased with the formation of etch channels without any change in the concentrations of Na'. Li+. K', and A13+. Therefore. it appears Cat+ and Mg++ are localised to the highly distorted lattice surrounding a line defect and are preferrentially removed during etch channel formation.
Kouia-gun, Kanagawa Pref.,
IhTRODUCTIONIt is well known that electrodiffusion (sweeping) reduce the formation of etch channels. This effect. is influenced by the electrodiffusion conditions. including the electric field strength. electrode type and atmosphere. The etch channel formation conditions differs according to whether electrodiffusion takes place in a vacuum o r air atmosphere. Vacuum electrodiffusion produces etch channel free elements. [ l ] If done in air. however. the impurities originally present in the crystal. diffuse to the cathode and the airbone impurities are taken up by the crystal from the anode. [2]Electrodiffusion performed in a nitrogen atmospere leads to the same result as vacuum electrodiffusion. in that the synthetic crystal with a high etch channel density is converted to an etch channel-free crystal. [31 If electrodes of Cr and Au evaporated metallization are applied. etch channels are not form even when electrodiffusion is carried out in an air atmosphere.Extensive research was carried out on etch channels in quartz crystal.[5]-[12] Etch channels are formed as a result of the presence of line defects in the quartz crystal and of impurities segregating out along such line defects. These impurities have a highly selective solubility vis a vis the etchant. The mechanism by which etch channels are reduced through electrodiffusion. however. has not been fully expained . The present study was undertaken with a view to making this mechanism clear. To establish the relationship between the reduction in etch channel density and the electrodiffusion conditions. the latter were systematically altered in this investigation. 9 CH2965-...
