Volume 86, Issue 5, 01 September 1999
Index of content:
- DIELECTRICS AND FERROELECTRICITY (PACS 77)
86(1999); http://dx.doi.org/10.1063/1.371119View Description Hide Description
Fluorinated amorphous carbonthin films (a-C:F) for use as low-dielectric-constant interlayer dielectrics are deposited by helicon-wave plasma enhanced chemical vapor deposition. To improve their thermal stability, the feasibility of adjusting the fluorine-to-carbon (F/C) ratio by changing the deposition pressure was investigated. Decreasing the pressure increased the dissociation of a source fluorocarbon material in the plasma and decreased the F/C ratio of the depositedfilm. Both the thermal stability and the dielectric constant of the a-C:F films were increased as the F/C ratio was decreased. Thus, there is a tradeoff relationship between a low dielectric constant and high thermal stability and the tradeoff could be optimized by the pressure during deposition. The mechanism of the pressure dependency of the dielectric constant of a-C:F films was investigated by quantifying the contribution of each polarization and found that a decrease in the dielectric constant of a-C:F films can be attributed to decreases in the orientational and electronic polarizations.
86(1999); http://dx.doi.org/10.1063/1.371120View Description Hide Description
Dielectric and piezoelectric properties of single crystals polarized along the 〈001〉 crystallographic axes were investigated as a function of temperature and dc bias. Electromechanical coupling and piezoelectric coefficients better or comparable to those of lead-based (PZT), were found from 〈001〉-oriented orthorhombic crystals at 0 °C, as a result of crystallographic engineering. A rhombohedral crystal polarized along 〈001〉 also exhibited enhanced piezoelectric performance, i.e., and at −90 °C, superior to PZTs at the same temperature. It was found that the crystal structure determined the (in)stability of the engineered domain state in single crystals. Rhombohedral (3m) crystals at −100 °C exhibited a stable domain configuration, whereas depoling occurred in crystals in the adjacent orthorhombic phase upon removal of the E field.
86(1999); http://dx.doi.org/10.1063/1.371121View Description Hide Description
In this work, chargetransport through interpoly thin nitride/oxide stacked films, including nitride/oxide dual- and oxide/nitride/oxide tri-layer films, was studied. Extensive experimental results, concerning current conduction in single oxide layer, single nitride layer, nitride/oxide dual-layer, and oxide/nitride/oxide tri-layer films are presented. An effective investigation of the various mechanisms that can explain current conduction and charge trapping in these dielectrics was performed. To this aim, different approaches to transport modeling, namely, a classical current continuity model, a transmission model, and a two-step trap assisted model are proposed. The gains and trade offs offered by each model are pointed out. A comprehensive model for the conduction mechanisms in thin nitride/oxide stacked films is proposed.
86(1999); http://dx.doi.org/10.1063/1.371122View Description Hide Description
In situ observation of the -to-Pbnmstructuralphase transition in has been made mainly by transmission electron microscopy to understand features of the transition in samples with relatively large nonstoichiometry of more than Instead of the appearance of the superlattice reflection spot exhibiting the phase transition, only the diffuse maximum appears at and in the simple cubic reciprocal lattice below a transition temperature of about 190 K. The subsequent aging below also results in the local lattice destruction. These features found in the samples with large nonstoichiometry should be caused by both the nonstoichiometry and the strain field induced by the change in the crystal system in the transition.