Properties of stacked SrTiO3/Al2O3 metal-insulator-metal capacitorsThe x-ray induced visible luminescence of SrTi0 3 has been studied in the range 15-300 oK. An apparently single-emission band at 500 nm has been observed whose efficiency abruptly decreases at -30 oK. This luminescence band is proposed to be intrinsic and associated with the decay of a relaxed Ti + 30 3 -5 exciton. After 15 oK irradiation, a visible absorption spectrum which increases towards the infrared is produced and anneals out at -30 oK. It is suggested that the absorption is due to electron transition from a Ti+ 3 center to the conduction band, in accordance with recent ultraviolet photoemission spectroscopy data. The thermoluminescence spectrum after 15 oK irradiation has also been determined. The first glow peak at 30 oK appears to correlate well with the thermal decay of the irradiation-induced absorption. PACS numbers: 78.55.Hx, 61.80.Cb 9009J.

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Output diffraction efficiencies approaching 40% and input diffraction efficiencies approaching 3% have been achieved in photorefractive p-i-n quantum well diodes operating in the longitudinal Stark geometry. The device structure consists of a low-temperature-grown multiple quantum well isolated from the doped contacts by an intrinsic standoff layer of Al0.5Ga0.5As. All charge trapping and screening occurs within the quantum wells without the need for trapping in specialized buffer layers used in previous designs. This new design operates at lower voltages (18 V) and lower fields (6 V/μm) than previously demonstrated.