R. K. Pandey

Improved ferroelectric property of LaNiO3/Pb(Zr0.2Ti0.8)O3/LaNiO3 capacitors prepared by chemical solution deposition on platinized silicon

We report a technique to prepare top and bottom oxide electrodes of LaNiO3 (LNO) for lead zirconate titanate (PZT) films using a chemical solution deposition. LNO/PZT/LNO sandwich structures were prepared on platinized silicon by spin coating combined with rapid thermal annealing. Pt dots were sputtered on top of LaNiO3 film to serve as protective masks during etching of the uncovered LaNiO3 layer using dilute hydrochloric acid. For comparison, Pt/PZT/Pt capacitors were also prepared using the same processing conditions. Electrical measurements were carried out on both Pt/LNO/PZT/LNO/Pt and Pt/PZT/Pt structures. The remnant polarizations and coercive fields for these two capacitors are 17.4 and 21.4μC∕cm2, 71 and 81.5kV∕cm respectively at 5V. The leakage current density for the Pt/LNO/PZT/LNO/Pt structure is about 1.38×10−6A∕cm2 at 5V, which is lower than that of PZT deposited on Pt electrode. After 109 bipolar switching cycles, no significant change in remnant polarization was observed in the Pt/LNO/PZT/...

Highly a-axis-oriented Nb-doped Pb(TixZr1−x)O3 thin films grown by sol–gel technique for uncooled infrared dectors

Pb(Nb0.02Zr0.2Ti0.8)O3 thin films with thickness of 900nm were spincoated on platinized silicon substrate using the sol–gel method. X-ray diffraction and field emission scanning electron microscopy show that the films are highly a-axis-oriented with columnar structure. A large remnant polarization (Pr+) ∼92.2μC∕cm−2 was observed for as-grown films. The coercive field (Ec+) for these films was 159.3kV∕cm. Good pyroelectric properties are obtained as a result of large remnant and spontaneous polarization and their strong temperature dependence. The pyroelectric coefficient and figure of merit at room temperature (22°C) are 10.8×10−4Cm−2K−1 and 2.34×10−5Pa−1∕2, respectively.

Nonlinear current–voltage characteristics of ilmenite–hematite ceramic

Abstract Current–voltage ( I – V ) characteristics of solid solutions of ilmenite–hematite (IH) (1− x )FeTiO 3 · x Fe 2 O 3 , with x varying from 0 to 0.45, were studied. All compositions except x =0 exhibit a low-voltage varistor behavior. The switching voltage for these devices was found to be well below 10 V, with the lowest value being about 2 V. The nonlinear coefficient, α , of the devices varied between 1.75 and 3.7. These results indicate that varistors based on some members in the family of IH are suitable for protecting the Si-based microelectronic circuits from surge of transient currents.

Double-peak resistivity transport properties of La0.67Ca0.33MnO3 ceramics

Abstract Polycrystalline samples of La0.67Ca0.33MnO3 were prepared by solid-state reactions by varying the pelletization force and the sintering temperature. Lowering the sintering temperature gave rise to smaller grains and increased the overall resistivity of the ceramic. Partial melting was observed in the ceramics sintered at higher temperatures (1400–1500xa0°C). Additionally, these ceramics showed two distinct resistivity peaks. The resistivity peak near the magnetic transition (TC) was sharp, whereas the second peak was a broad one observed below TC.

SbSI Films for Ferroelectric Memory Applications

Films of ferroelectric antimony sulphoiodide (SbSI) were grown on platinized silicon substrates by pulsed laser deposition (PLD). The films were grown at room temperature and later annealed at 200-250 C in air for crystallinity. The Curie temperature (T C ) of these films was 17-21 C, whereas the peak dielectric constant was up to 5000. These films showed nonzero remnant polarization above T C up to a temperature of 40 C and a low leakage current density of around 10 m 6 A/cm 2 at 2V. SbSI films were integrated with colossal magnetoresistive La 0.67 Ca 0.33 MnO 3 (LCMO) thin film, which acts as a p-type semiconductor. The LCMO-SbSI heterostructures, with SbSI as a ferroelectric gate, showed a channel modulation of about 10%.

Low-voltage varistors based on La–Ca–Mn–O ceramics

Varistor-like highly nonlinear current–voltage (I–V) characteristics were observed in the ceramics of colossal magnetoresistive La–Ca–Mn–O at room temperature, which is above its magnetic transition temperature. The switching voltage of all devices studied was less than 5 V with a nonlinearity coefficient a in the range of 2.6–32. The microstructure of the grains and the grain boundary region changes as the pelletization pressure and sintering temperature are varied. The contribution of grain boundary region to the electronic properties increases as the grains become smaller, which resulted in higher values of a and higher resistivity of the ceramic. This effect was observed at lower pelletization force and sintering temperature. It was also observed that higher values of a were associated with a higher switching voltage. D 2002 Elsevier Science B.V. All rights reserved.

Integrated PNZT Structures for MEMS Gyroscope

The effect of processing on the ferroelectric and piezoelectric properties of sol-gel grown Pb1.1Nb0.04Zr0.2Ti0.8O3 (PNZT) thin films was investigated. The effective d 31 piezoelectric coefficient of as-grown films was measured using piezoelectrically actuated cantilevers. The results indicate that films annealed after each layer possess a significant internal field, leading to high piezoelectric coefficients in the as-grown PNZT films. But the films annealed in the final step possess a very small internal field, and, consequently, small piezoelectric response.

Predicted Frequency Response of Integrated Pyroelectric PNZT Infrared Detectors

Numerous studies have been carried out on the fabrication of ferroelectric lead titanate (PT) and lead zirconate titanate (PZT) thin films and their applications to pyroelectric sensors [1–3]. Not many efforts have been made to integrate the films with silicon technology. In this article, we report on the growth of lead-zirconium-titanates films doped with niobium (PNZT) by a sol-gel method on platinized Si substrates along with its characteristics for use in infrared sensor applications.

Characterization of integrated heterostructures of SbSI–La0.67Ca0.33MnO3

Abstract Heterostructures of ferroelectric antimony sulpho iodide (SbSI) and colossal magnetoresistive La 0.67 Ca 0.33 MnO 3 (LCMO) have been grown on NdGaO 3 substrates by pulsed laser deposition (PLD) technique. The integrated structure, with SbSI acting as a gate insulator and LCMO as a semiconductor channel, exhibited field effect along with a channel modulation of about 10%. This ferroelectric field effect has been observed at a voltage of only 2 V. The field effect was non-volatile, and very little change was observed in the channel resistance after more than 2 h. Polarization switching tests showed a small polarization loss of about 5% after more than 10 7 bipolar switching cycles.

Infrared Spectroscopy of Epitaxial Antimony Sulpho Iodide Thin Films

Thin films of antimony sulpho iodide (SbSI) were grown on platinized silicon substrates by the pulsed laser deposition method. As grown films were amorphous and annealing at 250 °C for 5 minutes introduced crystallinity in the films. Infrared reflectance measurements were done in the frequency range ~ 500 – 5000 cm -1 (wavelength ~ 2–20 µm). The reflectance measurements were taken at temperatures above and below the ferroelectric transition of SbSI ~ 20° C. The index of refraction for a (121) oriented film was determined to be 2.83 ± 0.35 at a temperature of 25.6 °C, and 2.80 ± 0.35 at a temperature of 9.6 °C. For a (002) oriented film, the index was 3.82 ± 0.48 at a temperature of 26.5 °C, and 3.76 ± 0.48 at a temperature of 8.0 °C. Pyro-optic coefficients of 1.5 x 10 -3 °C -1 for the (121) oriented film, and 3.2 x 10 -3 °C -1 for the (002) oriented film were obtained. These results are consistent with measurements done in the visible region, and demonstrate the potential of SbSI as an infrared detector material.