Aluminum and Hydroxide Defect Centers in Vacuum Swept Quartz

Abstract

Abstract : Vacuum swept quartz is characterized by infrared spectroscopic measurements both along the sweeping axis and by scanning small regions of the sample perpendicular to the sweeping axis. We observe large variations in the strengths of the as-grown OH- and A1-OH- defect related bands between the anode and cathode. In a vacuum swept sample, initially containing aluminum-sodium centers, a region depleted of as-grown OH- extends a short distance into the sample, with a corresponding sharp gradient in the A1-OH- related band. Electron spin resonance delta indicates that in this region of the sample 35 percent of the defects are in the form of aluminum-hole centers. A sample, initially containing aluminum-lithium centers, was air swept and then vacuum swept. Successive periods of vacuum sweeping deplete hydroxide defects near the anode and substantially decrease them near the cathode. Vacuum sweeping effects are accelerated by removing the surface layers and repolishing the crystal after successive short sweeping periods.