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The electrical responses, either structurally or chemically, at the interface between a SiO2 thin film and a single crystalline Si substrate are an important research subject in Si-based devices. Dielectric breakdown-induced epitaxial migration of Si into SiO2 has been reported as a degradation mechanism in field effect transistors. Here, we show a direct observation of electric field induced conversion of single crystalline Si to nonstoichiometric amorphous oxide starting from the Si/native oxide interface using in situ transmission electron microscopy. We further show that nanocrystalline Si can form in the amorphous oxide under a voltage bias of reversed polarity. Electron energy loss spectroscopy and energy dispersive X-ray spectroscopy analyses indicate that the observed amorphization process was caused by the oxidation of Si and the recrystallization process was caused by the reduction of nonstoichiometric amorphous silicon oxide. Both transitions are a result of field-driven directional migration of oxygen which originally comes from its native oxide layer. [ABSTRACT FROM AUTHOR]

The solid solution between the normal ferroelectric Pb(Zr(sub 1/2)Ti(sub 1/2))O(sub 3) (PZT) and relaxor ferroelectric Pb(Ni (sub 1/3)Nb(sub 2/3))O(sub 3) (PNN) was synthesized by the columbite method. The transistor between relaxor to normal ferroelectricity was typified by a quasilinear relationship between the diffuseness parameter Delta (sub gamma) and PZT mole fraction x.

Chemically modified (K0.5Na0.5)NbO3 compositions with finely tuned polymorphic phase boundaries (PPBs) have shown excellent piezoelectric properties. The evolution of the domain morphology and crystal structure under applied electric fields of a model material, 0.948(K0.5Na0.5)NbO3-0.052LiSbO3, was directly visualized using in situ transmission electron microscopy. The in situ observations correlate extremely well with measurements of the electromechanical response on bulk samples. It is found that the origin of the excellent piezoelectric performance in this lead-free composition is due to a tilted monoclinic phase that emerges from the PPB when poling fields greater than 14 kV/cm are applied. [ABSTRACT FROM AUTHOR]

The correlation between structure and electrical properties of lead-free (1-x)(Bi1/2Na1/2)TiO3-xBaTiO3 (BNT-100xBT) polycrystalline piezoceramics was investigated systematically by in situ synchrotron diffraction technique, combined with electrical property characterization. It was found that the morphotropic phase boundary (MPB) between a rhombohedral and a tetragonal phase evolved into a morphotropic phase region with electric field. In the unpoled material, the MPB was positioned at the transition from space group R3m to P4mm (BNT-11BT) with optimized permittivity throughout a broad single-phase R3m composition regime. Upon poling, a range of compositions from BNT-6BT to BNT-11BT became two-phase mixture, and maximum piezoelectric coefficient was observed in BNT-7BT. It was shown that optimized electrical properties are related primarily to the capacity for domain texturing and not to phase coexistence. [ABSTRACT FROM AUTHOR]

The temperature dependence of both polarization and electric-field induced strain was investigated for (1-x)Bi(Mg1/2Ti1/2)O3–xPbTiO3 (x=0.36, 0.37, and 0.38), with the morphotropic phase boundary located at x=0.37. Remanent polarization (Pr) and maximum polarization (Pmax) of all compositions are enhanced with increasing temperature up to 175 °C, which is rationalized as improved domain switching due to reduced tetragonality (c/a). The hysteresis during unipolar electric cycling tends to decrease with increase in the fraction of tetragonal phase. Temperature dependent x-ray diffraction demonstrates that switched non-180° domains are stable against thermal depoling above 200 °C, which indicates that the currently investigated materials are suitable for high temperature applications. This promising high-TC piezoelectric is further discussed with reference to oxygen octahedron of the tilted R3c and untilted R3m space groups and the tolerance factor (t). [ABSTRACT FROM AUTHOR]

The temperature dependence of both polarization and electric-field induced strain was investigated for (1-x)Bi(Mg1/2Ti1/2)O3–xPbTiO3 (x=0.36, 0.37, and 0.38), with the morphotropic phase boundary located at x=0.37. Remanent polarization (Pr) and maximum polarization (Pmax) of all compositions are enhanced with increasing temperature up to 175 °C, which is rationalized as improved domain switching due to reduced tetragonality (c/a). The hysteresis during unipolar electric cycling tends to decrease with increase in the fraction of tetragonal phase. Temperature dependent x-ray diffraction demonstrates that switched non-180° domains are stable against thermal depoling above 200 °C, which indicates that the currently investigated materials are suitable for high temperature applications. This promising high-TC piezoelectric is further discussed with reference to oxygen octahedron of the tilted R3c and untilted R3m space groups and the tolerance factor (t). [ABSTRACT FROM AUTHOR]

Ceramics solid solutions within the ternary perovskite system Bi(Zn1/2Ti1/2)O3-BiScO3-BaTiO3 were synthesized via solid-state processing techniques. The crystal structure of sintered ceramics was analyzed by x-ray diffraction. A stable perovskite phase was obtained for all compositions with a BaTiO3 content greater than 50 mol %. Furthermore, a change in symmetry from pseudocubic to tetragonal was observed as the mole fraction of BaTiO3 increased. Dielectric measurements show a dielectric anomaly associated with a phase transformation over the temperature range of 30 °C–210 °C for all compositions. Examination of the polarization hysteresis behavior revealed weakly nonlinear hysteresis loops. With these data, ferroelectric phase diagrams were derived showing the transition between the pseudocubic relaxor behavior to the tetragonal normal ferroelectric behavior. This transition was also correlated with changes in the diffuseness parameter. [ABSTRACT FROM AUTHOR]