High Performance Quartz.

Recent experiments in the laboratory and under factory conditions and a re-assessment of the literature aimed at developing techniques for preparing high performance quartz especially r-bar quartz for SAWS, radiation hard quartz and low channel and dislocation density material are reported. We find r-bar material to be preferrable for SAW wafers because the wafer is cut parallel to the growing face resulting in greater homogeneity and increased yield. For the wafer sizes required 5degree X growth (growth on a face rotated 5degree from (0001)) requires 6 months while wafers large enough for devices can be grown in 6 weeks on r-bar seeds (growth on (10 1 bar 1) face). Possible procedures for Al impurity reduction so as to improve radiation resistance are described. Recrystallization of natural quartz nutrient and crushing the grown crystals for nutrient does not result in significant purification unless several recrystallizations are employed. A single recrystallization is shown to be equivalent to single pass zone refining and would not be expected to result in significant purification. Procedures for using a very low Al content SiO sub 2 -glass as nutrient are described. Etch Channels are shown to be decorated dislocations and measures which reduce dislocations: using dislocation free (DLF) seeds, reducing particulate inclusions and minimizing seed-grown material lattice mismatch are effective. Additional means of channel reduction may depend upon avoiding decoration of dislocations by Na.