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Science 13 August 1993:
Vol. 261. no. 5123, pp. 897 - 899
DOI: 10.1126/science.261.5123.897
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Articles

High-Density Nanosecond Charge Trapping in Thin Films of the Photoconductor ZnODEP

Chong-yang Liu 1, Horng-long Pan 1, Marye Anne Fox 1, and Allen J. Bard 1

1 Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712

An electrooptical memory effect is observed with solid thin films of the photoconductor zinc-octakis(beta-decoxyethyl) porphyrin (ZnODEP) sandwiched between two optically transparent electrodes. Upon irradiation with the simultaneous application of an electric field, electron-hole pairs are generated and separated within the photoconductive layer. These electron-hole pairs become "frozen" within the films when the irradiation is interrupted. These trapped charges can be released by irradiation of the cell, resulting in a transient short-circuit photocurrent. No cross talk between adjacent memory elements separated by sim0.2 micrometer (a density of 3 gigabits per square centimeter) was detected. The charge storage system is robust and nonvolatile. The response time for the write-read beam is in the subnanosecond range, and no refreshing is required for long-term retention of trapped charges.

Submitted on April 12, 1993
Accepted on July 1, 1993

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Science. ISSN 0036-8075 (print), 1095-9203 (online)