Nonbolometric laser-induced voltage signals in YBa sub 2 Cu sub 3 O sub 7 minus. delta. thin films at room temperature

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.2313· OSTI ID:5411397

Kleinhammes, A; Chang, C L; Moulton, W G; Testardi, L R ^[1]

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1. Department of Physics, Florida State University, Tallahassee, Florida (USA)

We report on detailed studies of laser-induced voltage signals observed in unbiased YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} thin films at room temperature. The induced signals are measured as a function of incident energy, bias current, light polarization, and wavelength. The observed signals are remarkable because of their magnitude, up to 2 V across 4 {Omega} at 30 mJ/cm{sup 2}, and because they represent potentials which are forbidden by the known crystal symmetry of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} if two obvious explanations, pyroelectricity and off-diagonal thermoelectricity, are considered. The signal proves to be independent of the polarization of light as well as its wavelength for {lambda}=1064, 532, and 355 nm. Our measurements provide strong evidence that the observed signals do not have a bolometric origin. The signal amplitude is proportional to the magnitude of the incident energy and not to its energy density. The time constant of the bolometric response, determined by applying a bias current, is different from that of the transient. The dependence of the time constant, {tau}{sub {ital s}}, of the transient on the film thickness is not unique. For films with thicknesses below 4000 A, {tau}{sub {ital s}} agrees with simulated thermal diffusion times. Thicker films appear to show time constants independent of thickness, in contrast with predictions for thermal diffusion. Although the reflectivity is a symmetric function of the angle of incidence about the normal, the voltage signals are not.

• OSTI ID: 5411397
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 44:5; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
ELECTRO-OPTICAL EFFECTS
COPPER OXIDES
HIGH-TC SUPERCONDUCTORS
LASER RADIATION
INCIDENCE ANGLE
YTTRIUM OXIDES
AMPLITUDES
BOLOMETERS
CRYSTALS
ELECTRIC POTENTIAL
ENERGY DEPENDENCE
MEDIUM TEMPERATURE
POLARIZATION
SIGNALS
SUPERCONDUCTING FILMS
SYMMETRY
THERMAL DIFFUSION
THICKNESS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
DIFFUSION
DIMENSIONS
ELECTROMAGNETIC RADIATION
FILMS
MEASURING INSTRUMENTS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties