Accession Number : ADP006659

Title :   Photoresponse from Thin Ferroelectric Films of Lead Zirconate Titanate,

Corporate Author : CALIFORNIA INST OF TECH PASADENA

Personal Author(s) : Thakoor, Sarita ; Thakoor, Anil P. ; Bernacki, Stephen E.

Report Date : 05 APR 1991

Pagination or Media Count : 16

Abstract : Bulk (ceramic as well as single crystal) ferroelectric materials are known for their remanent-polarization-dependent photoresponse: a photocurrent (and a photo-emf), when illuminated by light with a wavelength close to the bandgap of the material. This paper reports on observation of a similar photoresponse from sol-gel derived polycrystalline thin films of lead zirconate titanate (PZT) . The internal field due to the remanent polarization modulates this net photoresponse from the ferroelectric material. Thin film ferroelectric capacitors were fabricated in a sandwich geometry with a transparent tol electrode. on illumination with approximately 365nm wavelength (PZT bandgap 3.5 eV) light pulse, photocurrent profiles from such capacitors correspond to their distinct remanent polarization memory states. Further, such a read-out has negligible effect on the magnitude of the remanent polarization and therefore it is a potential candidate as a non-destructive readout of the nonvolatile memory states. The observed photocurrent has two components: first, a transient spike coincident with the onset of the illumination pulse, and second, a steady dc photocurrent which prevails as long as the light is 'ON' . The steady current response exhibits a weak dependence on the polarization whereas the transient response exhibits a distinct polarization dependence. Our study suggests that the predominant contribution to the steady photovoltaic current is due to the asymmetric pair of Schottky junctions at the two interfaces of the ferroelectric film with the top and bottom electrodes respectively.

Descriptors :   *ELECTRODES, *FERROELECTRIC MATERIALS, *LEAD TITANATES, *POLARIZATION, CAPACITORS, FILMS, GELS, GEOMETRY, ILLUMINATION, INTERFACES, INTERNAL, JUNCTIONS, LIGHT, LIGHT PULSES, MATERIALS, NETS, NONVOLATILE MEMORIES, OBSERVATION, POLYCRYSTALLINE, PROFILES, PULSES, RESPONSE, THIN FILMS, TRANSIENTS, ZIRCONATES.

Subject Categories : Ceramics, Refractories and Glass
      Electricity and Magnetism

Distribution Statement : APPROVED FOR PUBLIC RELEASE