Philip S. Brody

Mechanism for the high voltage photovoltaic effect in ceramic ferroelectrics

The high-voltage photo-emf seen in poled ferroelectric ceramics is explained as the result of light-induced carriers screening an internal field within the bulk of individual grains. The internal field itself is explained as the result of the shielding by equilibrium carriers of the potential produced by the spontaneous polarization. Less-than-band-gap emf’s are produced across individual grains; these emf’s add in ceramics to produce the high-voltage photo-emf. A model yields the polarity and magnitude of the photo-emf, the dependence on temperature, remanent and spontaneous polarization, dielectric constant and grain size. The calculated and experimental results are in general agreement.

Optomechanical bimorph actuator

Abstract An optomechanical bender bimorph–a device which responds to incident illumination by bending–is described. Expressions for the bimorph action are derived and the results of tests are reported.

Lead Zirconate-Titanate Thin Films Prepared by the Laser Ablation Technique

Lead zirconate-titanate (PZT) thin films were prepared by the laser ablation technique. The PZT (Zr/Ti=53/47) target was irradiated using a focused q-switched Nd:YAG laser (15 ns, 100 mJ at 1.064 μ;m). The as-deposited films were amorphous as indicated by X-ray powder patterns, but crystallized readily with brief annealing above 650°C. The dielectric constant and the resistivity of the crystallized films were studied using a parallel-plate type capacitor structure.

Processing microscope using phase-conjugate illumination generated by self-pumping in barium titanate

Abstract A processing microscope which uses a reconstructed phase-conjugate optical field has been developed. The microscope produces phase-contrast images which show gradients in phase with respect to a direction in the plane of the microscope slide. The phase conjugate of the optical field produced by passing a coherent beam through the slide passes back through the shifted slide to produce phase-contrast patterns which are viewed with a microscope. The phase conjugate is excited from a photorefractive volume phase hologram in a barium titanate crystal where it has formed by self-pumping. The microscope images are digitally processed to remove coherent artifacts.

Dynamic holographic method of imaging phase objects

We describe a new method of imaging phase objects which uses the self-phase-conjugating phenomenon in barium titanate and a technique of incomplete aberration removal.

Temperature dependence of the short circuit photocurrent in ferroelectric ceramics

Abstract Recent experimental results for the temperature dependence of the short circuit photocurrent in barium titanate, and PZT ceramic are interpreted as indicating that the photocurrent is essentially a drift current proportional to the product of the temperature dependent high voltage photo-emf and the temperature dependent electron mobility along the c axis as measured in a reduced single crystal.

Photovoltaic and other outputs from pulsed laser illuminated ferroelectrics

Abstract Polarized lithium niobate single crystals and barium titanate ceramic samples are investigated under 15 ns pulsed laser illumination. Pyroelectric, piezoelectric and anomalous photovoltaic outputs are distinguished. Both prompt and long-lived photovoltaic currents are observed.

Preparation, microstructure, and ferroelectric properties of laser-deposited thin BaTiO3 and lead zirconate-titanate films

Abstract Ferroelectric thin films of BaTiO3 and lead zirconate titanate, PbZr0.53Ti0.47O3 (PZT), have been prepared by pulsed excimer laser deposition. The microstructure and crystallography of these films have been studied by scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDX), transmission electron microscopy (TEM), x-ray diffraction (XRD), and differential scanning calorimetry (DSC). Electrical properties, including remanent polarization, dielectric loss, and dielectric constant, have been measured. Also, switched remanent polarization has been measured under conditions of continuous cycling.

Microscopy Using Optical Phase Conjugation In A Hybrid Analog/Digital System

We describe and illustrate a useful optical/electronic imaging technique that employs real-time holography and the phenomenon of optical phase conjugation. The technique is developed as method for coherent light microscopy in which images are produced which show gradients in optical phase retardation. The technique can also be used to produce images which contain only the moving elements of a phase object. We illustrate both applications of the techniques, the first with phase-gradient micrographs of common biological objects, and the second with images of a microscopic subject in which only elements characterized by intrinsic motions appear.

Ferroelectric and dielectric properties of sol-gel and excimer-laser-deposited lead zirconate titanate and barium titanate films

Abstract Switched remanent polarization was measured as a function of accumulated switching cycles for a variety of ferroelectric films using sinusoidally driven hysteresis loops. Switched remanent polarization and dielectric constant and loss were also obtained as a function of the cycling frequency. PZT films with niobium additives appeared to lose switched remanent polarization with accumulated cycles at a lesser rate than films without niobium. The switched remanent polarization was found to decrease with increasing frequency, which we attribute to the effect of grain size. Also, a decrease of dielectric constant with increasing frequency and an increase of dielectric constant with increased applied voltage are attributed to the effects of domain wall motion contributions to dielectric constant.