Search

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.

By a sol–gel method, a BiFeO3 (BFO) capacitor is fabricated and connected with the control thin film transistor (TFT). Compared with a control thin-film transistor, the proposed BFO TFT achieves 56% drive current enhancement and 7–28% subthreshold swing (SS) reduction. Moreover, the effect of the proposed BiFeO3 capacitor on IDS-VGS hysteresis in the BFO TFT is 0.1–0.2 V. Because dVint/dVGS > 1 is obtained at a wide range of VGS, it reveals that the incomplete dipole flipping is a major mechanism to obtain improved SS and a small hysteresis effect in the BFO TFT. Experimental results indicate that sol-gel BFO TFT is a potential candidate for digital application.

Nowadays, the development of GPS (Global Positioning System) technology has become mature, and has begun to develop in the direction of high-precision positioning and navigation. Navigation data such as position, speed, and heading provided by GPS are very important in military or commercial fields. However, in addition to improving the accuracy of positioning, its reliability must also be considered. Therefore, RTK (Real Time Kinematic) differential positioning technology is used to perform real-time error correction and basic inertial components consist of gyroscope, accelerometer, and magnetic compass are used to compensate and improve reliability. In this study, a car is used as a vehicle to experiment the route near the campus. The collected XYZ position coordinate data of the non-difference, differential positioning, and original vehicle are calculated by MATLAB offline operation to obtain $\lambda($longitude), $\Phi$ (latitude), h (height), and the data sensed by integrated inertial elements in the GPS signal shaded roads as auxiliary navigation, and then compare it with the existing and non-differential positioning methods to obtain a more optimized drawing path. The map achieves the compensation effect. In this study, the position of the shaded road is obtained by the second integration of the gyroscopic azimuth change and the heading angle of the magnetic compass through the accelerometer signal. The Extended Kalman Filter algorithm is used as its solution to estimate position, speed and heading of the vehicle in real time to achieve high accuracy and high reliability of real-time positioning and navigation.

In this study, the Mg doping effects on the nanostructural dependence of photoluminescence and the photosensing properties in Zn1−xMgxO (x = 0.01, 0.03, and 0.05) nanorod arrays were systematically examined. The vertical-aligned nanorod arrays were separately grown on ZnO-seeded n-Si substrates via a low-temperature hydrothermal process. X-ray diffraction analysis revealed that all Zn1−xMgxO nanorod arrays exhibited the same preferentially c-oriented wurtzite structure. Images of all the Zn1−xMgxO nanorod arrays provided by field emission scanning electron microscope showed that both the length and diameter of the Zn1−xMgxO nanorod arrays increased with increasing Mg doping concentration. Also, an enhanced blue-shifted ultraviolet (UV) emission and a reduced visible emission were observed from the photoluminescence spectra of the Zn1−xMgxO nanorod arrays. The former indicated the decrease of defects and the latter indicated the enhancement of the crystallinity and the increase in optical bandgap. Current–voltage curves were separately measured in the dark and under UV illumination. Finally, the mechanism of the Mg doping effects on the corresponding defects, bandgap, and UV photosensing characteristics of the Zn1−xMgxO nanorod arrays was investigated in detail.

By a sol–gel method, a BiFeO3 (BFO) capacitor is fabricated and connected with the control thin film transistor (TFT). Compared with a control thin-film transistor, the proposed BFO TFT achieves 56% drive current enhancement and 7–28% subthreshold swing (SS) reduction. Moreover, the effect of the proposed BiFeO3 capacitor on IDS-VGS hysteresis in the BFO TFT is 0.1–0.2 V. Because dVint/dVGS > 1 is obtained at a wide range of VGS, it reveals that the incomplete dipole flipping is a major mechanism to obtain improved SS and a small hysteresis effect in the BFO TFT. Experimental results indicate that sol-gel BFO TFT is a potential candidate for digital application.

Electrical conduction mechanism and bipolar resistive switching properties of the manganese oxide thin films resistive random access memory (RRAM) devices for high resistive status and low resistive status (HRS/LRS) were investigated and discussed. The electrical and physical properties of post-treatment manganese oxide thin films for different oxygen concentration parameters were measured by x-ray diffraction (XRD) and operation current versus applied voltage ( I-V ) measurement. For I-V curves in different temperature, the ohmic conduction, space charge limited conduction (SCLC), schottky emission conduction, and hopping conduction mechanism of manganese oxide RRAM devices were discussed and verified in initial metallic filament path forming process. Finally, the excess oxygen ions, vacancy, and defect factor resulting in bipolar and unipolar resistive switching behavior of thin films RRAM devices will be explained and investigated by metallic filament path forming model.

The bipolar switching properties and electrical conduction mechanism of vanadium oxide thin-film resistive random-access memory (RRAM) devices obtained using a rapid thermal annealing (RTA) process have been investigated in high-resistive status/low-resistive status (HRS/LRS) and are discussed herein. In addition, the resistance switching properties and quality improvement of the vanadium oxide thin-film RRAM devices were measured by x-ray diffraction (XRD) analysis, x-ray photoelectron spectrometry (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and current–voltage (I–V) measurements. The activation energy of the hopping conduction mechanism in the devices was investigated based on Arrhenius plots in HRS and LRS. The hopping conduction distance and activation energy barrier were obtained as 12 nm and 45 meV, respectively. The thermal annealing process is recognized as a candidate method for fabrication of thin-film RRAM devices, being compatible with integrated circuit technology for nonvolatile memory devices.

Pr-doped ZnO thin films (Zn1−xPrxO) (x = 0.00, 0.01, 0.02, 0.04) were prepared on fluorine-doped tin oxide substrates by means of the sol–gel method and spin coating technology, followed by rapid thermal annealing treatment at 800 °C. The influence of Pr content on the structural and optical properties of the Zn1−xPrxO thin film was examined and discussed. The wurtzite hexagonal structural characteristics were investigated by X-ray diffraction analysis, and Pr3+ substitution for Zn2+ ions was indicated. Finally, the typical bipolar current-voltage switching curves and electrical conduction model of Zn1−xPrxO film resistive random access memory devices were discussed and investigated for low resistance state/high resistance state in the initial forming process.

FeS2 pyrite films are used in a variety of applications including solar cells and, the potential scope for their utilization is increasing as their synthetic methods become more economical while maintaining or enhancing their high light absorption coefficients. The glass substrate temperature dependence on the formation of FeS2 pyrite films was investigated with respect to their optical and physicochemical properties. During the thermochemical spraying process the temperature was varied in the range of 190-290 °C. FeS2 nanocrystalline (40-70 nm) films, formed as a result of atmospheric spraying with glass substrate temperatures above 260 °C, were observed by SEM. Opto-electronic studies revealed that the nanocrystalline films had a direct band gap (1.3-1.6 eV) with a high light absorption coefficient (α > 7 × 104 cm−1 for λ

Indium tin oxide (ITO; Indium oxide with tin doping) nanowires were first prepared via the electrochemical deposition and an oxidization method based on an AAO template. FE-SEM results show the synthesized ITO nanowires to have an approximate length of 8–10 μm with an aspect ratio close to 167. ITO nanowires with an In/Sn weight ratio of 8.8 (∼9:1) were observed from EDS. The crystal structure of ITO nanowires showed that all the peaks within the spectra can be indexed to In2O3 with a cubic structure. The ITO nanowire is single-crystalline determined from selected area electron diffraction (SAED) patterns. An optical energy gap (Eg) of the ITO nanowire is 3.8 eV.

Bi0.9Gd0.1FeO3 (BGFO) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by using the sol–gel technology. The effects of annealing temperature (400–700 °C) on microstructure and multiferroic properties of thin films were investigated. The X-ray diffraction analysis showed that the BGFO thin films had an orthorhombic structure. The thin films showed ferroelectric and ferromagnetic properties with remanent polarization (2Pr) of 10 μC/cm2, remnant magnetization (2Mr) of 2.4 emu/g and saturation magnetization (Ms) of 5.3 emu/g. A small leakage current density (J) was 4.64×10−8 A/cm2 under applied field 100 kV/cm. It was found that more than one conduction mechanism is involved in the electric field range used in these experiments. The leakage current mechanisms were controlled by Poole–Frenkel emission in the low electric field region and by Schottky emission from the Pt electrode in the high field region.

Praseodymium and niobium-substituted bismuth titanate (Bi 3.96 Pr 0.04 Ti 2.95 Nb 0.05 O 12 , BPTNO) thin films were deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by a sol–gel technology. The effects of annealing temperature (500 ~ 800 °C) on microstructure and electric properties of thin films were investigated. X-ray diffraction analysis shows that the BPTNO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The intensities of (117) peak increases with increasing annealing temperature. With the increase of annealing temperature from 500 °C to 800 °C, the grain size of BPTNO thin films increases. The highly (117)-oriented BPTNO thin films exhibits a high remnant polarization (2 P r ) of 48 μC/cm 2 and a low coercive field (2 E c ) of 110 kV/cm, fatigue free characteristics up to > 10 8 switching cycles. A small leakage current density ( J ) was 6.23 × 10 − 8 A/cm 2 at 200 kV/cm. The leakage current mechanisms were controlled by Poole–Frenkel emission in the low electric field region and by Schottky emission in the high field region.

Surface plasmon resonance mediated by Gold (Au) nanoparticles (NPs) was employed to enhance the ultraviolet (UV) response of p-Si/n-ZnO nanorod (NR) heterojunction photodetectors (HPDs). In the ZnO NRs with Au NP covering, the photoluminescence spectrum shows that the band-to-band emission of ZnO (384 nm) is increased by a magnitude of 3, and the deep-level emissions (450-700 nm) are drastically decreased as compared with HPDs without coverings of Au NPs. Such a result increases UV-to-visible rejection ratio from 214 to 6180 and it attributes that the defect-level emissions of ZnO induce surface plasmon resonance in Au NPs and then enhances the emissions, exciting a large quantity of electrons crossing over the Au NP/ZnO interface barrier. Consequently, these electrons are transferred to the ZnO conduction band from the Au NPs, causing a photocurrent gain and the quantum efficiency is as high as 1157% at 2 V reverse bias.

ZnO and Y-doped ZnO nanocrystalline films were separately fabricated on the glass substrates by sol-gel spin-coating method. X-ray diffraction patterns of the films show the same wurtzite hexagonal structure and (0 0 2) preferential orientation. Scanning electron microscope images show that grain size and thickness of the nanocrystalline films decrease with increasing doping concentration. The decrease of optical bandgap with the increase of Y doping is deduced from the transmittance spectra. Temperature-dependent resistivity reveals a semiconductor transport behavior for all ZnO and Y-doped ZnO nanocrystalline films. The resulting conductivity originates from the combination of thermal activation conduction and Mott variable-range hopping (VRH) conduction. In the high-temperature range, the temperature-dependent resistivity can be described by the Arrhenius equation, ${\sigma}$ $(T)$ = ${\sigma}_{0}$ exp[ $-(E_{a}$ /kT)], which shows the thermal activation conduction. The activation energy $E_{a}$ increases from 0.47 meV for ZnO film to 0.83 meV for Zn $_{0.98}$ Y $_{0.02}$ O film. On the contrary, in the low-temperature range, the temperature-dependent resistivity can be fitted well by the relationship, ${\sigma}$ ( $T)$ = ${\sigma}_{h}$ $_{0}$ exp[ $-(T_{0}$ / $T)$ $^{1/4}$ ], which indicates the behavior of Mott VRH. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the ZnO and Y-doped ZnO nanocrystalline films are affected by Y doping.

The transparent ZnO and Zn0.96Fe0.04O nanocrystalline films were deposited on the glass substrates by sol–gel method followed by repaid thermal annealing treatment. The grain size of the ZnO films was decreased by the doping of Fe. X-ray diffraction measurements of the films showed the same wurtzite hexagonal structure and preferential orientation along the c-axis. Temperature dependence resistivity showed a semiconductor transport behavior for both compositions. At high temperature region, the transport mechanism can be fitted with semiconductor behavior by Arrhenius equation, σ(T) = σ0 exp[−(Ea/kT)m] with m = 1. The activation energy Ea is increased from 0.47 meV for pure ZnO film to 0.69 meV for Zn0.96Fe0.04O film obtained from equation. At low temperature region, the resistivity can be fitted well with the behavior of Mott variable range hopping, σ(T) = σh0 exp[−(T0/T)n] with n = 1/4. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the Zn1 − xFexO films are affected by the doping of Fe in the Zn1 − xFexO films.

In this paper, the chalcopyrite CuInSe2 thin films were fabricated from a selenization of electrodeposited Cu-In layers. In this study, the electrodeposition time of the In layer was set, but that for the Cu layer was not. The thin films were selenized in a sealed glass tube with pure Se powder by three different Cu layer samples at various electrodeposition times at 500 °C for 2 hours. An FE-SEM image of the sample shows that the copper-rich product has irregular agglomerates with a dense surface. The X-ray diffraction patterns show CuInSe2 peaks for all samples. However, the X-ray diffraction pattern reveals CuSe2 peaks when the electrodeposition time of the Cu layer increases. On the other hand, the band gap (Eg) of the samples decreases from 1.15 to 1.07 eV when the Cu/In ratio increases.

Sm–Ta co-doped Bi 4 Ti 3 O 12 (Bi 3.96 Sm 0.04 Ti 2.92 Ta 0.08 O 12 , BSTTO) thin films were fabricated on Pt(111)/Ti/SiO 2 /Si(100) substrates by sol–gel technology, and the microstructure, dielectric, ferroelectric and leakage current properties of the thin films were investigated. BSTTO thin film exhibits a high remanent polarization (2 P r ) of 46.2 μC/cm 2 and a low coercive field (2 E c ) of 102 kV/cm, fatigue-free characteristics up to ≧ 10 8 switching cycles. The 2 P r of the BSTTO thin film is larger than that of the Bi 4 Ti 3 O 12 thin film (2 P r = 26 μC/cm 2 ). In addition, the leakage current density of Sm–Ta co-doped Bi 4 Ti 3 O 12 thin film is 2.56 × 10 − 8 A/cm 2 , which is lower than that of the Bi 4 Ti 3 O 12 thin film (1.0 × 10 − 5 A/cm 2 ). These improvements in the ferroelectric and leakage current properties can be attributed to the enhanced stability of the oxygen in the Ti–O octahedron layer by the substitution with Sm and Ta for Bi 3 + and Ti 4 + in A-site and B-site of the BTO thin film, respectively.

Herein one-dimensional Sm-doped ZnO nanostructures have been successfully fabricated by a simple hydrothermal method at a low temperature of 90 � C. The effect of Sm doping on the microstructure, photoluminescence and magnetism of ZnO nanorods is also investigated. FE-SEM images show that the average diameter of the Sm-doped ZnO nanorods is obviously smaller than that of ZnO nanorods. Photoluminescence spectrum of Sm-doped ZnO nanorods shows a slightly red-shifted decrease of UV emission and an enhancement of photoluminescence performance of visible emission. Raman spectrum of Sm-doped ZnO nanorods reveals that the peak intensity corresponding to the E2 high mode decreases significantly compared with that of the pure ZnO nanorods, indicating the restraint of crystallization. Room temperature ferromagnetism is observed from magnetization curves of both ZnO and Sm-doped ZnO nanorods. The increase of the saturation magnetization induced by the Sm doping in the ZnO nanorods reveals an association with the increase of oxygen vacancies and oxygen interstitials.

Herein transparent Zn1-xFexO nanocrystalline films have been prepared on glass substrates by sol-gel method followed by rapid thermal annealing treatment. The effecs of Fe doping on the microstructure, transmittance and magnetism of Zn1-xFexO nanocrystalline films are investigated. The x-ray diffraction patterns of all compositions show the same wurtzite hexagonal structure with the space group P63/mc. FE-SEM images show uniform spherical grains of all Zn1-xFexO nanocrystalline films in which the grain size decreases progressively from 38.85 nm (x = 0.00) to 15.35 nm (x = 0.04). Red shift of the absorption edges is obtained from the optical transmittance spectra from 372 nm of undoped ZnO film to 367 nm of Zn0.96Fe0.04O film. The corresponding wide band gap energy of undoped ZnO film is 3.2986 eV which decreases slightly by 0.0191 eV of Zn0.96Fe0.04O film. The saturation magnetization increases with the increase of Fe concentration. All Fe-doped ZnO films exhibit feromagnetic hysteresis curves which can b...

Tantalum-substituted Bi4Ti3O12 (Bi4Ti3-x/5Tax/5O12, BTTO) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by sol–gel technology. The effects of various processing parameters, including Ta content (x=0∼0.08) and annealing temperature (500∼800 °C), on the growth and properties of thin films were investigated. X-ray diffraction analysis shows that the BTTO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. With the increase of Ta content, the grain size of film decreased slightly, and highly (117)-oriented BTTO films were obtained in the composition of x=0.06. Ta doping on the B-site of Bi4Ti3O12 could induce the distortion of oxygen octahedral and decrease the oxygen vacancy concentration by a compensating effect. The highly (117)-oriented BTTO thin films with x=0.06 exhibits the maximum remanent polarization (2Pr) of 50 μC/cm2 and a low coercive field (2Ec) of 104 kV/cm, fatigue free characteristics up to ≧ 108 switching cycles.

The Bi0.85 Eu0.15 FeO3 /Bi3.2 Y0.8 Ti3 O12 bilayer thin films were prepared on Pt(111)/Ti/SiO 2/Si(100) substrates using the sol-gel process and annealed by rapid thermal annealing in various annealing environments (ambient atmosphere and oxygen). The multiferroic/ferroelectric bilayer thin films were composed of 0.8-μ m thickness Bi0.85 Eu0.15 FeO3 and 0.2-μ m thickness of Bi3.2 Y0.8 Ti3 O12 thin film. The effects of annealing atmospheres (ambient atmosphere and oxygen) on the growth and properties of thin films were investigated. The results show that the intensities of the (117) diffraction peak of Bi3.2Y0.8Ti3O 12 film and (110) diffraction peak of Bi0.85Eu0.15FeO3 annealed in oxygen is stronger than those annealed in an ambient atmosphere. The Bi0.85Eu0.15FeO3/Bi3.2Y0.8Ti3O12 bilayer thin films annealed in the oxygen atmosphere exhibit the maximum remanent polarization (2\mbi Pr) and remnant magnetization (2Mr) of 26 μ C/cm2 and 3.44 emu/g, respectively. The improved magnetic and ferroelectric properties can be attributed to the elimination of defects, such as oxygen vacancy and vacancy complexes.

Bi0.9Eu0.1FeO3 (BEFO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using the sol-gel method and rapid thermal annealing in an oxygen atmosphere. The effects of annealing temperature (400 ~ 700 C) on microstructure and multiferroic properties of thin films were investigated. The X-ray diffraction analysis showed that the BEFO thin films had an orthorhombic structure. The thin films showed ferroelectric and ferromagnetic properties with remanent polarization (2Pr) of 15 μC/cm2 and remnant magnetization (2Mr) of 4.2 emu/g. The leakage current density (J) of the BEFO thin film annealed at 700 °C was 4.25t10-8& A/cm2 at 150 kV/cm. The leakage current was affected not only by the microstructure but also by the interface between the Pt electrode and the BEFO thin films. Moreover, it was found that more than one conduction mechanism was involved in the electric field range used in these experiments. In the low electric field region, the leakage current was controlled by Poole-Frenkel emission. However, the mechanism could be explained by Schottky emission from the Pt electrode in the high electric field region.

Titanium oxide (TiO 2 ) thin films are prepared by the sol–gel method and annealed at 600 °C by conventional (CTA) and rapid thermal annealing (RTA) processes on fluorine-doped tin oxide -coated glass substrates for application as the work electrode for the dye-sensitized solar cells (DSSC). TiO 2 thin films are crystallized using a conventional furnace and the proposed RTA process at annealing rates of 5 °Cmin −1 and 600 °Cmin −1 , respectively. The TiO 2 thin films are characterized by X-ray diffraction, scanning electron microscopy and Brunauer–Emmett–Teller analysis. Based on the results, the TiO 2 films crystallized by RTA show better crystallization, higher porosity and larger surface area than those of CTA. The short-circuit photocurrent and open-circuit voltage values increased from 5.2 mAcm −2 and 0.6 V for the DSSC with the CTA-derived TiO 2 films to 8.3 mAcm −2 and 0.68 V, respectively, for the DSSC containing RTA-derived TiO 2 films.

Nanocrystalline ZnO thin films were prepared by the sol-gel method and annealed at 600 °C by conven- tional (CTA) and rapid thermal annealing (RTA) processes on fluorine-doped tin oxide (FTO)-coated glass substrates for application as the work electrode for a dye-sensitized solar cell (DSSC). ZnO films were crystallized using a con- ventional furnace and the proposed RTA process at anneal- ing rates of 5 °C/min and 600 °C/min, respectively. The ZnO thin films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM) analyses. Based on the results, the ZnO thin films crystallized by the RTA process presented better crystallization than films crystallized in a conventional furnace. The ZnO films crystallized by RTA showed higher porosity and surface area than those prepared by CTA. The results show that the short-circuit photocur- rent (Jsc) and open-circuit voltage (Voc) values increased from 4.38 mA/cm 2 and 0.55 V for the DSSC with the CTA- derived ZnO films to 5.88 mA/cm 2 and 0.61 V, respectively, for the DSSC containing the RTA-derived ZnO films.

Bi3.2Gd0.8Ti3O12 (BGTO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using the sol-gel method and rapid thermal annealing in an oxygen atmosphere. The effects of annealing temperature (500–800°C) on microstructure and electrical properties of thin films were investigated. X-ray diffraction analysis shows that the BGT thin films have a bismuth-layered perovskite structure with preferred (117) orientation. The intensities of (117) peaks increases with increasing annealing temperature. The leakage current density (J) was 3.69×10−8 A/cm2 at 200 kV/cm. It was found that the leakage current was affected not only by the microstructure but also by the interface between the Pt electrode and BGTO thin films. In the low electric field region, the leakage current was controlled by Poole–Frenkel emission. In addition, the mechanism can be explained by Schottky emission from the Pt electrode in the high electric field region.

The preferred (002) orientation zinc oxide (ZnO) nanocrystalline thin films have been deposited on FTO-coated glass substrates by sol–gel spin-coating technology and rapid thermal annealing for use in dye-sensitized solar cells (DSSC). The effects of preannealing temperature (100 and 300°C) on the microstructure, morphology and optical properties of ZnO thin films were studied. The ZnO thin films were characterized by X-ray diffraction (XRD), scanning electron microscopic (SEM) and Brunauer–Emmett–Teller (BET) analysis. The photoelectric performance of DSSC was studied by I–V curve and the incident photon-to-current conversion efficiency (IPCE), respectively. From the results, the intensities of (002) peaks of ZnO thin films increases with increasing preannealing temperature from 100°C to 300°C. The increase in pore size and surface area of ZnO films crystallized at the increased preannealing temperature contributed to the improvement on the absorption of N3 dye onto the films, the short-circuit photocurrent (J sc) and open-circuit voltage (V oc) of DSSC. The higher efficiency (η) of 2.5% with J sc and V oc of 8.2 mA/cm2 and 0.64 V, respectively, was obtained by the ZnO film preannealed at 300°C.

Praseodymium-substituted bismuth titanate (Bi 3.2 Pr 0.8 Ti 3 O 12 , BPTO) thin films were successfully deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by spin coating with a sol-gel technology and rapid thermal annealing. The effects of annealing atmospheres (vacuum, ambient atmosphere and oxygen) on the growth and properties of thin films were investigated. The results show that the intensity of the (117) diffraction peak of Bi 3.2 Pr 0.8 Ti 3 O 12 film annealed in oxygen is stronger than those annealed in ambient atmosphere and vacuum. The XRD spectra demonstrated that a highly (117) orientation could be obtained when the Bi 3.2 Pr 0.8 Ti 3 O 12 thin film was annealed in an oxygen-sufficient environment. The BPTO thin films annealed in oxygen atmosphere exhibits the maximum remanent polarization (2P r ) of 49 μC/cm 2 and a low coercive field (2E c ) of 130 kV/cm, fatigue free characteristics up to ≥10 11 switching cycles. These results indicate that the BPTO thin film is useful in nonvolatile ferroelectric random access memory applications.

Nanocrystalline anatase TiO 2 thin films with different thicknesses (0.5-2.0 μm) have been deposited on ITO-coated glass substrates by a sol-gel method and rapid thermal annealing for application as the work electrode for dye-sensitized solar cells (DSSC). From the results, the increases in thickness of TiO 2 films can increase adsorption of the N3 dye through TiO 2 layers to improve the short-circuit photocurrent (J sc ) and open-circuit voltage (V oc ), respectively. However, the J sc and V oc of DSSC with a TiO 2 film thickness of 2.0 μm (8.5 mA/cm 2 and 0.61 V) are smaller than those of DSSC with a TiO 2 film thickness of 1.5 μm (9.2 mA/cm 2 and 0.62 V). It could be due to the fact that the increased thickness of Ti0 2 thin films also resulted in a decrease in the transmittance of TiO 2 thin films thus reducing the incident light intensity on the N3 dye. An optimum power conversion efficiency (η) of 2.9% was obtained in a DSSC with the TiO 2 film thickness of 1.5 μm.

ZnO-coated TiO2 (ZTO) thin films were deposited on ITO substrates by a sol–gel method for application as the work electrode for dye-sensitized solar cells (DSSCs). The I–V curve and the incident photon-to-current conversion efficiency (IPCE) value of DSSCs for ZTO thin films were studied and compared with single TiO2 films. The results show that the short-circuit photocurrent (J sc) and open-circuit voltage (V oc) values increased from 3.7 mA/cm2 and 0.68 V for the DSSCs with a single TiO2 film to 4.5 mA/cm2 and 0.72 V, respectively, for the DSSCs with a ZTO thin film. It indicated that the DSSCs with a ZTO thin film contributed to provide an inherent energy barrier that suppressed charge recombination significantly. In addition, the higher IPCE value in the ZTO thin film is attributed to the better charge separation by a fast electron transfer process using two semiconductors with different conduction band edges and energy positions.

High-performance pyroelectric infrared (IR) detectors have been fabricated using tantalate-doped lithium niobate LiNb 1 -x Ta x 0 3 (abbreviated as LNT, with x= 0-1.0) thin films deposited on Pt(1 1 11)/TilSiO 2 /Si(100) substrates by diol-based sol-gel processing, in which, tantalate (Ta) is adopted as dopant in lithium niobate. The randomly oriented LNT thin film exhibits a relatively small dielectric constant and a large pyroelectric coefficient. The pyroelectric characteristics of detectors with various tantalate contents, as a function of modulation frequency, were investigated. It was found that LiNb 0,8 Tau 0.2 O 3 had the largest voltage responsivity of 7020 (V/W) at 70 Hz, and a specific detectivity (D*) of 7.76 x 10 7 cm Hz 1/2 /W at 200 Hz. These results indicate that the LNT thin film with x=0.20 is most suitable for application as high-performance pyroelectric thin-film detectors.

Yttrium-substituted bismuth titanate (Bi 3.2 Y 0.8 Ti 3 O 12 , BYT) thin films were successfully deposited on Pt(1 1 1)/Ti/SiO 2 /Si(1 0 0) substrates by spin coating with a sol–gel technology and rapid thermal annealing. The effects of annealing temperature (500–800 °C) on microstructure and electrical properties of thin films were investigated. X-ray diffraction analysis shows that the BYT thin films have a bismuth-layered perovskite structure with preferred (1 1 7) orientation. The intensities of (1 1 7) peaks increases with increasing annealing temperature. With the increase of annealing temperature from 500 to 800 °C, the grain size of BYT thin films increases. The highly (1 1 7)-oriented BYT thin films exhibit a high-remnant polarization (2 P r ) of 58 μC/cm 2 and a low-coercive field (2 E c ) of 116 kV/cm, fatigue free characteristics up to >10 8 switching cycles. The leakage current density ( J ) were 4.38×10 −8 A/cm 2 at 200 kV/cm. These results indicate that the highly (1 1 7)-oriented BYT thin film is useful in nonvolatile ferroelectric random access memory applications.

Recently, researches indicate that grain boundaries and interfaces can be the major factors of magnetoresistance effects, which has attracted renewed interests on the colossal magnetoresistance materials. In this article, the magnetic behaviours and magnetotransport properties of (La0.7Pb0.3MnO3)1-x(Fe2O3)x composites have been investigated. Ferromagnetism is gradually suppressed as the weight percentage of Fe2O3 is increased. Saturation magnetization (MS) decreases from 78.7 emu/g for x = 0.0 to 60.6 emu/g for x = 0.2, while ferromagnetic transition temperature (TC) remains around 346K for all composites. The resistivity increases significantly as the x value increases in these composites. It is suggested that the introduction of Fe2O3 into the composites acts as a separation layer between La0.7Pb0.3MnO3 grains. The enhancement of magnetoresistance has been verified with the addition of Fe2O3 into the composites. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on the temperature dependence of resistivity in La 0.7-x Pr x Pb 0.3 MnO 3 (x=0, 0.5, 0.7) bulk samples in order to explore the hopping transport behavior with the Coulomb effects for the colossal magnetoresistance materials. The experimental observations in La 0.7-x Pr x Pb 0.3 MnO 3 (x=0.5, 0.7) bulk samples reveal the exponential temperature dependence of resistivity p(T) ∞ exp[(T 1 /T) n with n = 1/2, when system was the paramagnetic (PM) insulator at the high temperature range (T>Tp). Evidence for the hopping conduction with Coulomb effects is presented By using the approximate method of the VRH conduction in the localization regime base on Efros and Shklovskii model [A. L. Efros and B. I. Shklovskii, J. Phys. C, Solid State Phys. 8, L49 (1975)], the localization length of eg electrons can be estimated with the relationship, ξ=2.8e 2 /(4πe 0 κk B T 1 ). The reasonable results of localization length can be evaluated to explain the possibility of the presence of the Coulomb interactions in these CMR materials.

In this work, the magnetization behavior of two maganite oxide systems, La0.7–xNdxPb0.3MnO3 and La0.7–xSmxPb0.3MnO3, has been synthesized. The partial replacement of La ions by Nd or Sm results in a considerable decrease in the ferromagnetic ordering temperature TC. Moreover, clearly irreversible behavior in the field-cooling and zero-field-cooling curves at a low applied field shows the short-range spin order phase. These facts are in agreement with the smaller ionic radii of Nd (0.127 nm) and Sm (0.124 nm) ions in contrast to La ion (0.136 nm) with the corresponding larger distortion of perovskite structure. The saturation magnetization MS is increased as Nd content is increased which provides a relative contrast with the decrease of MS by the increase of Sm content. This can be interpreted in terms of the competition between the suppression of ferromagnetism due to structure tuning induced by the small ionic radius of the interpolated cation into the La-site and the increase of ferromagnetic spins due to the introduction of magnetic Nd or Sm ions with f -shell electrons. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The influence of La substitution by rare-earth elements on the magnetization behaviors of perovskite oxides, La0.7−x Lnx Pb0.3 MnO3 ( Ln = Pr , Nd, Gd, Dy, Sm and Y), is investigated. The replacement of La ion by Pr, Nd, Gd, Dy, Sm or Y results in a considerable decrease in the ferromagnetic ordering temperature T C and clearly irreversible behavior in the FC–ZFC curves showing a short-range spin order phase. The fact is in agreement with the smaller ionic radii of Pr, Nd, Gd, Dy, Sm and Y ions in contrast to La ion and the corresponding larger distortion of perovskite structures. The saturation magnetization M S increases as Pr or Nd content increases while M S decreases as Sm or Y content increases. Moreover, the saturation magnetization M S increases and then decreases as Gd or Dy content increases. These results can be explained in terms of the competition between the increase of ferromagnetically interacting spins due to the introduction of magnetic ions with f-shell electrons and suppression of ferromagnetism due to structure tuning induced by the small ionic radius of the interpolated cation into the La-site.

The preferred (002) orientation Zinc oxide ( ZnO ) nanocrystalline thin films have been deposited on ITO-coated glass substrates by means of sol-gel spin-coating technology and rapid thermal annealing for use in dye-sensitized solar cells (DSSC). The effects of annealing temperature (400 ~ 700 ° C ) on the microstructure and morphology of ZnO thin films were studied. With the increase of heating temperature from 400 °C to 700 °C, the grain size of ZnO thin films decreases from 80 to 10 nm. The decreases in grain size of ZnO thin films contributed to the improvement on the absorption of dye onto the films. The ITO/ZnO/RuL 2 (NCS) 2 electrodes with high absorption in the wide range containing visible light reveal that the nanoporous structure can adsorb easily the dye and can be expected in the application of DSSC.

Polycrystalline single phase oxides, La 0.7-x Nd x Pb 0.3) MnO 3 (0.3≤x≤0.7), have been synthesized by a standard ceramic fabrication method. A phenomenological model is proposed to describe the magnetization process, and to fit the experiment data of hysteresis loops under different composition ratio. The magnetic hysteresis behavior can be modeled by the formula of [Formula: see text]. The resulted model can satisfy the experiment data ranging from 0.005T to 5T. Explanations on the fitting coefficients of these compounds are addressed.

LiTaO 3 thin films were deposited on Pt / Ti / SiO 2/ Si substrates by means of a sol-gel spin-coating technology and rapid thermal annealing (RTA). The influence of various annealing treatments on the characteristics of the thin films were studied by varying the single-annealed-layer thickness (50 ~ 200 nm ) and heating temperatures (500 ~ 800° C ) of the samples. Experimental results reveal that the single-annealed-layer strongly influences grain size, dielectricity and ferroelectricity of LiTaO 3 thin films. The grain size of LiTaO 3 thin film decreases slightly with increasing thickness of the single-annealed-layer, and highly c-axis orientated LiTaO 3 films can be obtained for a single-annealed-layer of 50 nm. When the thickness of the single-annealed-layer was increased from 50 to 200 nm, the relative dielectric constant of LiTaO 3 thin film decreased from 65 to 35, but the dielectric loss factor (tanδ) was increased. The LiTaO 3 films with the single-annealed-layer of 50 nm showed excellent ferroelectric properties in terms of a remanent polarization ( P r) of 12.3 μ C /cm2 (Ec ∼ 60 kV/cm), and a low current density of 5.2×l0-8 A /cm2 at 20 kV/cm.

High-performance pyroelectric infrared detectors have been fabricated using Lithium tantalite (LiTaO3) thin films deposited on Pt(111)/Ti/SiO2/Si(100) substrates by diol-based sol-gel method and rapid thermal annealing (RTA) technique. The dielectric and pyroelectric properties of IR detectors of LiTaO3 thin films crystallized by conventional and RTA processes are investigated. Experimental results reveal that the heating rate will influence strongly on dielectricity and pyroelectricity of LiTaO3 thin films. The voltage responsivities (Rv) measured at 80 Hz increase from 5496 to 8455 V/W and the specific detecivities (D∗) measured at 300 Hz increase from 1.94 × 108 to 2.38 × 108 cmHz1/2/W with an increase of heating rate from 600 to 1800∘C/min. However, the voltage responsivity and the specific detecivity decrease with heating rate in excess of 1800∘C/min. The results show that the LiTaO3 thin film detector with a heating rate of 1800∘C/min exists both the maximums of voltage responsivity and specific detecivity.

LiNbTa x O 3 thin films were successfully deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by spin coating with a diol-based sol-gel technology and rapid thermal annealing. The effects of various processing parameters, including Ta content (0) and heating temperature (500 ~ 800 °C), on the growth and properties of thin films were investigated. With the increase of Ta content, the grain size of film decreased slightly, and the maximum f factor (the degree of c -axis orientation) of the films were obtained in the composition of x = 0.2. As the composition of film varied from x = 0 to x = 1, the relative dielectric constant of film increased from 33 up to 62, and the dielectric loss factor (tan δ ) also increased from 0.00374 to 0.00686, respectively. The coercive field, Ec , and remanent polarization, Pr , decreased but pyroelectric coefficient, γ , increased from 2.76 × 10 −8 up to 4.51 × 10 −8 C/cm 2 K. The pyroelectric figures of merit, Fv and Fm , indicated that film with Ta content of 20 mol% and heating temperature of 700 °C exhibited the optimized pyroelectric characteristics and could be applied for high-performance pyroelectric thin-film detectors.

Lithium tantalite (LiTaO3) thin films have been deposited on Pt(111)/SiO2/Si(100) substrates by means of sol–gel spin-coating technology. Using a diol-based precursor solution and rapid thermal processing (RTP), highly c-axis oriented LiTaO3 thin films are obtained and the degree of orientation is increased with an increase of the heating rate. By changing the heating rate (600–3000 °C/min) and heating temperature (500–800 °C), the effects of various processing parameters on the growth of films are investigated. With the increase of heating rate, the grain size of LiTaO3 thin films decreases markedly, and the relative dielectric constant (er) increases from 28 up to 45.6. It was found that the dielectric loss factor (cosδ) decreased, and the ferroelectric properties were improved by the increase of heating rate. The figures of merit (Fv and Fm) indicate that the LiTaO3 thin film with a heating rate of 1800 °C/min is suitable for application as a high-performance pyroelectric thin-film detector.

Pb1-xMgxTiO3 (PMT) thin films (x=0–0.08) were deposited onto Pt/SiO2/Si substrates by diol-based sol-gel processing. The influence of various processing methods on the characteristics of the thin films was studied by varying the magnesium contents and heating temperatures (500–800 °C) of the samples. In the present study, the relative dielectric constant (er) of the PMT thin films increased from 25.8 to 91.8 as the magnesium content increased. The coercive field (Ec) and the remanent polarization (Pr) decreased as the magnesium content increased, but the dielectric loss factor (cosδ) and the pyroelectric coefficient (p) increased. The PMT thin films with x=0.06 exhibited the largest figures of merit for voltage responsivity and specific detectivity. These results indicate that the PMT thin film with x=0.06 was most suitable for application to high-performance pyroelectric thin-film detectors.

The LiTaO3 thin films were prepared by a diol-based sol-gel method and crystallized by conventional and RTA processes. Based on the results, the c-axis orientation of the films crystallized by the RTA process presented better crystallization than those crystallized in a conventional furnace. The remanent polarization (P r ) and the coercive field (Ec) of the films crystallized in a conventional furnace were about 2.4 μ C/cm2 and 87 kV/cm. On the contrary, for LiTaO 3 films crystallized by the RTA method, the remanent polarization (P r ) and the coercive field (Ec) were about 10.7 μC/cm2 and 45 kV/cm, respectively.

LiTaO3 thin films were deposited onto Pt(111)/SiO2/Si(100) substrates using the sol-gel method and rapid thermal annealed in an oxygen atmosphere with a heating rate of 600∼3000°ptC/min. The leakage currents of the lithium tantalite thin films were measured and its leakage current mechanism was investigated. It was found that the leakage current was affected by the interface between the Pt electrode and LiTaO3 thin films. In the low electric field region, the leakage current was controlled by Poole-Frenkel emission. On the other hand, the mechanism can be explained by Schottky emission from the Pt electrode in the high field region.

Well-defined ZnO and Sm-doped nanorods have been successfully fabricated by a low temperature hydrothermal process. The XRD patterns of both compositions with a single diffraction peak (002) show the same wurtzite hexagonal structure. The radius of Sm-ZnO nanorods observed by FE-SEM is smaller than that of pure ZnO, indicating a reduction of the growth rate by the doping of Sm. Ferromagnetism is observed from the results of the magnetization measurements. The increase of the saturation magnetization and decrease of coercivity reveal an association with the increase of oxygen vacancies induced by the doping of Sm in the nanorods.