Volume 89, Issue 4, 15 February 2001
Index of content:
- DIELECTRICS AND FERROELECTRICITY (PACS 77)
89(2001); http://dx.doi.org/10.1063/1.1325378View Description Hide Description
Dielectric relaxation and steady-state leakage currents were studied over a range of bias voltages for Pt-electroded capacitors in which the 50-nm-thick dielectric layer was sputter deposited at 480 °C. A pronounced polarity dependence in the current–voltage characteristic of the capacitors was observed. Dielectric relaxation in the films showed a Curie–von Schweidler time dependence for intervals of 3–200 s duration after application of a voltage step. The relaxationcurrent density was found to depend linearly on electric field for fields up to 700 kV/cm and nonlinearly at higher fields. In addition to the Curie–von Schweidler relaxationcurrents, a time-dependent leakage current was detected under high voltage bias conditions. An empirical model developed to describe leakage currents in these films is presented.
89(2001); http://dx.doi.org/10.1063/1.1337600View Description Hide Description
We have used a near-field scanning microwavemicroscope to image domain structure and quantitatively measuredielectricpermittivity and nonlinearity in ferroelectric crystals at 8.1 GHz with a spatial resolution of 1 μm. We imaged ferroelectric domains in periodically poled and deuterated triglycine sulfate (DTGS) with a signal-to-noise ratio of 7. Measurement of the permittivity and nonlinearity of DTGS in the temperature range 300–400 K shows a peak at the Curie temperature, K, as well as reasonable agreement with thermodynamic theory. In addition, the domain growth relaxation time shows a minimum near We observe coarsening of ferroelectric domains in DTGS after a temperature quench from 360 to 330 K and evaluate the structure factor.
89(2001); http://dx.doi.org/10.1063/1.1339853View Description Hide Description
The effect of aging on some piezoelectric properties, including and in 1–3 compositetransducers has been evaluated in this article. The spontaneous changes of properties of piezocomposites (lead zirconate titanate/epoxy) and piezoceramic under zero external stress was measured at 5 days and 500 days after poling. The results show that the aging behavior in piezoelectriccomposites is very much dependent on the ceramic content. The composite material behaves similar to a piezoceramic at high volume fraction of ceramic, i.e., greater than 25 vol. %. At low volume fraction of ceramic, however, the rate of aging is much higher in piezoelectriccomposite compared to that of the piezoceramic. At lower than 25 vol. % of ceramic, it was seen that the aging rate increases with decreasing the ceramic content.
89(2001); http://dx.doi.org/10.1063/1.1326463View Description Hide Description
Silicon dioxide was deposited on a capacitor by the plasma-enhanced chemical-vapor deposition(PECVD) method. We have been investigated the mechanism of blister formation on the PECVDcapacitor. The blisters were observed at the temperature of in atmosphere, while in and Ar atmosphere blisters were not formed even at Hydrogen evolution analysis from the PECVD layer showed a sharp peak near The results indicated that the accumulation of water-vapor pressure developed by chemical reaction between oxygen and hydrogen could be the dominant mechanism of blister formation in PECVDcapacitors.
89(2001); http://dx.doi.org/10.1063/1.1331341View Description Hide Description
The polarization reversal process of tetragonal thin films has been intensively studied using conventional hysteresis and rectangle pulse measurements. Decreasing the voltage level of the pulses significantly slows down the polarization switching to the range of milliseconds. The switching current response shows a Curie–von Schweidler behavior over a broad time range. The transient current and the frequency dependence of the loops of these films compared to the properties of ferroelectricsingle crystals show some similarities but also significant differences. The theoretical models of the classical ferroelectric phase transition and especially the conditions of the pulse measurements in single crystals and thin films are discussed. It leads to the conclusion that it is not the domain wall structure and domain wall motion that determine the polarization reversal but dissipative polarization processes which can take place in both ferroelectric and nonferroelectric high-k dielectric thin films.