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When Nd doping in BiNdFeO (BNFO) film exceeds 10%, the two diffraction peaks (104)/(110) merge into one sharp single peak with increasing addition of Nd. It seems that a phase structural distortion can be obtained due to the substitution of Nd3+ ion for Bi3+ ion. For ferroelectric properties, among all Nd-doped (0%–20%) BiFeO3 capacitors, the BNFO capacitor with 10% Nd doping shows a higher Pr value due to a phase structural distortion and a lower leakage current. In a resistive-capacitive circuit diagram, the transient response of the voltage (V FE) across the BNFO capacitor can be measured. We demonstrate that the capacitance value d Q t d V FE t is negative in the spike interval of V FE(t), with the result that the negative capacitance of BNFO with a 10% Nd doping capacitor can obviously improve the I DS–V GS characteristics of a control thin-film transistor.

Ferroelectric polymer/ceramic bilayer thin films composed of polar β-phase polyvi-nylidene fluoride (PVDF) and 1-µm-thick polycrystalline lead titanate (PbTiO3) thin films were prepared, using a sol–gel method. The influence of various processing parameters on the characteristics of PVDF/PbTiO3 thin films was studied by varying the thickness of PVDF thin films (100–580 nm). The results show that the surface of the obtained PVDF film was smooth with less lower porosity above the PbTiO3 film, enabling a significant decrease in the leakage current of bilayer thin films. Although the coercive field (Ec), remanent polarization (Pr) and pyroelectric constant (p) of bilayer thin films decreased with the increase of PVDF thin film thickness, the deposition of PVDF thin films onto the PbTiO3 films caused the leakage current (J) measured at 40 kV/cm to decrease from 1.57 ×10-6 A/cm2 to 3.86 ×10-7 A/cm2 as well as the relative dielectric constant (er) from 63 to 20. The figures of merit (FV and Fm) due to relative low-dielectric constant (er) revealed that good infrared responses of bilayer thin films can be utilized in their application to detectors.

Hereby ZnO and Al-doped ZnO nanorods were fabricated on the silicon substrate by a low temperature hydrothermal process at 90 °C. The nanorods were prepared to study the Al doping effect on their structural, optical and magnetic properties. The Al-doped nanorods exhibited a c-axis (002) oriented wurtzite hexagonal structure as that of ZnO nanorods. Then, photoluminescence spectra showed an increase of visible emission peak intensity indicating the increase of defects in the nanorods. The peak intensity of E2 high mode as shown in Raman shift spectra decreased with the introduction of Al-dopant and also proved the increase of defects concentration and the suppression of crystallization in Al-doped ZnO nanorods. Finally, the hysteresis loops revealed the room temperature ferromagnetism of both compositions. As compared with ZnO nanorods, Al-doped ZnO nanorods showed a remarkable increase of saturation magnetization due to the increase of crystal defects.

Tantalum-doped TiO2 thin films [(TiO2)1-x (Ta2O5) x , x=0–0.8%] were prepared on fluorine-doped tin oxide (FTO)-coated substrates by sol–gel technology for uses in dye-sensitized solar cells (DSSCs). The effects of Ta content on the growth and properties of the TiO2 thin films were investigated. The crystallization and microstructures of the thin films were examined by X-ray diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller analyses. The performance of DSSCs based on Ta-doped TiO2 thin films was also studied. From the obtained results, the increases in J sc and V oc may be due to the increased electron concentration of TiO2 thin film and the flat-band potential of the TiO2 shifted by tantalum doping, respectively. The optimum properties of DSSCs of V oc=0.68 V, J sc=7.84 mA/cm2, FF=45.1%, and η=2.4% were obtained using the Ta-doped TiO2 thin film with x=0.5%.

High-performance pyroelectric infrared (IR) detectors have been fabricated using lithium tantalite (LiTaO3) thin films deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the diol-based sol–gel method. The thermal isolation of detecting elements was achieved by anisotropic wet etching of the back of the silicon substrate. In order to reduce the thermal mass and thermal time constant of the detector, the sensing element was fabricated on a thin membrane. The effects of membrane thickness on the response of pyroelectric IR detectors were studied by changing the membrane thickness (20–350 µm). As the membrane thickness decreased, the voltage responsivity (R v) increased from 4300 up to 8398 V/W, and the specific detectivity (D *) also increased from 1.2×108 to 2.7×108 cm·Hz1/2/W. Experimental results reveal that the thermally isolated detectors with membrane thickness of 20 µm exhibit excellent sensitivity.

Calcium-modified lead titanate (PCT) thin film pyroelectric infrared (IR) detectors were fabricated on Pt(111)/SiO2/Si(100) substrates using a diol-based sol–gel process. The randomly oriented PCT thin film, which has not undergone the poling treatment, exhibits a relatively small dielectric constant and a large pyroelectric coefficient. The pyroelectric properties of PCT thin film point detectors with various Ca contents on modulation frequency are measured and compared. The optimized composition of PCT thin film IR detectors was found to be the PCT(25), which exhibits a large voltage responsivity of 4533 (V/W) at 20 Hz and a specific detectivity (D *) of 6.45×107 cmHz1/2/W at 100 Hz. The results show that Pb1-x Ca x TiO3 thin film with x = 0.25 [PCT(25)] was most suitable for application to the pyroelectric thin film IR detector.

Polycrystalline thin films of Ca-modified lead titanate (PCT) were deposited on Pt/SiO2/Si substrates using a diol-based sol–gel process. Calcium acetylacetonate hydrate was adopted as a starting material instead of the calcium acetate or calcium nitrate tetrahydrate used conventionally. By changing the Ca content (5–35 mol%) and heating temperature (500–800°C), the influences of various processing parameters on the characteristics of thin films were studied. With the increase of the Ca content, the relative dielectric constant (ε r) of PCT thin film increased from 43 to 70 at the heating temperature of 700°C. It was found that the coercive field (E c) and the remanent polarization (P r) decreased, but the pyroelectric coefficient (γ) increased with an increase of Ca content. The results reveal that PCT thin film with a Ca content of 25 mol% exhibits the largest figures of merit for the voltage responsivity and the specific detectivity at a heating temperature of 700°C.