Search

GaAs p-i-n solar cells are studied using electroreflectance (ER) spectroscopy, light beam induced current (LBIC) mapping and photovoltaic characterization. Using ER measurements, the electric field across the pn junction of a wafer can be evaluated, showing 167 kV/cm and 275 kV/cm in the built-in condition and at &minus, 3 V reverse bias, respectively. In order to understand the effect of the interval between metal grids on the device&rsquo, s solar performance, we performed LBIC mapping and solar illumination on samples of different grid spacings. We found that the integrated photocurrent intensity of LBIC mapping shows a consistent trend with the solar performance of the devices with various metal grid spacings. For the wafer used in this study, the optimal grid spacing was found to be around 300 &mu, m. Our results clearly show the importance of the metal grid pattern in achieving high-efficiency solar cells.

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.

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.

Bi0.8Pr0.2Fe0.95Mn0.05O3/Bi3.96Gd0.04Ti2.95W0.05O12 (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO2/Si(100) substrates by using the sol-gel method with rapid thermal annealing. The BPFMO/BGTWO thin films exhibited well-saturated ferromagnetic and ferroelectric hysteresis loops because of the electro-magnetic coupling induced by the MF/FE structure. The remnant magnetization (2Mr) and remnant polarization (2Pr) were 4.6 emu/cm3 and 62 μC/cm2, respectively. Moreover, the bipolar I-V switching curves of BPFMO/BGTWO bilayer thin films resistive random access memory (RRAM) devices were discussed, and investigated for LRS/HRS.

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.

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.

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.

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.

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.

This paper presents an investigation on the magnetoresistance properties of the polycrystalline manganite oxides, La0.7−xNdxPb0.3MnO3 (x=0.0, 0.1, 0.5 and 0.7). We demonstrate that the magnetoresistance ratio is enhanced with the increase of Nd content due to the suppression of spin scattering in the presence of an applied magnetic field. We find that the magnetoresistance shows an increase with decreasing temperatures at low temperatures. These features have been conventionally attributed to spin-polarized tunneling at grain boundaries. The temperature dependence of the magnetoresistance can be described quite well by an expression of the type a+b/(T+c). At high temperatures the magnetoresistance ratio increases with increasing temperature and the resistivity shows the existence of the variable range hopping with Coulomb effects for x=0.5 and 0.7.

Bi4Ti3.96Nb0.04O12 thin films were successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by a sol–gel method and rapid thermal annealing. The effects of Nb-substitution and annealing temperature (500–800°C) on the microstructure and ferroelectric properties of bismuth titanate thin films were investigated. X-ray diffraction analysis reveals that the intensities of (117) peaks are relatively broad and weak at annealing temperatures smaller than 700°C. With the increase of annealing temperature from 500°C to 800°C, the grain size of Bi4Ti3.96Nb0.04O12 thin films increases. The Bi4Ti3.96Nb0.04O12 thin films annealed at 700°C exhibit the highest remanent polarization (2Pr), 36 μC/cm2 and lowest coercive field (2Ec), 110 kV/cm. The improved ferroelectric properties can be attributed to the substitution of Nb5+ to Ti4+ in Bi4Ti3O12 assisting the elimination of defects such as oxygen vacancy and vacancy complexes.

Tantalum doped TiO2 thin films ((TiO2)1−x (Ta2O5)x, x=0, 0.1%, 0.3%, 0.5%, 0.8%) were prepared on ITO-coated substrates by means of the sol–gel method and spin coating technology followed by rapid thermal annealing treatment (RTA). The effects of various processing parameters, including Ta content (x=0–0.8%) and annealing temperature, on the growth and properties of thin films were investigated. Structural characteristics by X-ray diffraction analysis indicated that the doping of Ta2O5 in the TiO2 without change the anatase structure of TiO2 thin films. The optical transmittance of (TiO2)1−x(Ta2O5)x thin films decrease from 50% down to 20% with increasing the Ta2O5 concentrations from x=0.00 to x=0.8%. The absorption coefficient shows energy gap were decreased with increasing Ta2O5 content from 2.932 eV for x=0.00 to 2.717 eV for x=0.8%. Doping TiO2 with Ta2O5 can lower its band gap and shift its optical response to the visible region.

We have prepared Zn1−x Y x O (x=0 and 0.01) tubes to study its structural and photoluminescent properties. A pore wetting process of porous polycarbonate templates with the liquid precursor and following thermal treatment were utilized for preparing the Zn1−x Y x O tube structure. Using the polycarbonate template with pore size of about 2 μm diameter, the Zn1−x Y x O tubes were obtained. Photoluminescence (PL) spectroscopy was used to measure optical emissions from 350 to 650 nm with a He-Cd laser. The results of the PL spectra show that the Zn1−x Y x O tubes have evident emission peaks at the UV (about 380 nm) and visible (around 500 to 650 nm) region. The emission peak at the UV region was slightly shifted to higher wavelengths with increasing Y content. Meanwhile, the green and yellow emission peaks intensity increases as Y content increases. These results are explained by the structure tuning and oxygen deficiency with the introduction of Y.

Bi0.9Gd0.1FeO3 (BGFO) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates using the sol-gel method. The thin films showed ferromagnetic properties with remnant magnetization (Mr) of 1.2 emu/g and saturation magnetization (Ms) of 5.3 emu/g. It was found that more than one conduction mechanism is 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. On the other hand, the mechanism can be explained by Schottky emission from the Pt electrode in the high field region.

The Y-doped ZnO nanocrystalline films were deposited on the glass substrates by sol-gel method. X-ray diffraction measurements of the films showed the same wurtzite hexagonal structure and preferential orientation along the c-axis. The grain size of the ZnO films was decreased by the doping of Y. Temperature dependence resistivity showed a semiconductor transport behavior for the nanocrystalline films. 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. On the contrary, 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 nondoped ZnO film to 0.83 meV for Zn0.98Y0.02O film obtained from equation. The results demonstrate that the crystallization and the corresponding carrier transport behavior of the Y-doped ZnO films are affected by the doping of Y.

The transport properties in La0.7−xYxPb0.3MnO3 (0.0 ⩽ x ⩽ 0.2) is investigated. The substitution of La3+ ions by smaller nonmagnetic Y3+ leads to greater spin disorder and induces variations in the magnetotransport behavior. From resistivity versus temperature curves a metal–insulator transition phenomenon is observed at the transition temperature, TP, decreases as the Y content increases. The resistivity is well fitted using the equation ρ(T) = ρnexp[(T∗/T)n] with n = 1/4 and n = 1/2 at high and intermediate temperatures, respectively. The characteristic temperature T∗ varies with Y content in a manner consistent with the localization model of variable range hopping. Below TP, resistivity varies as a function of power law contributions, ρ = ρ0 + ρ2T2 + ρ5/2T5/2, corresponding to the electron scattering processes in the ferromagnetic phase.

Well-defined ZnO and Sm -doped nanorods have been successfully fabricated by a low temperature hyderthermal process. The XRD patterns of both compositions with 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 the reduction of growth rate by the doping of Sm . Ferromagnetism is observed from the results of magnetization measurement. The increase of the saturation magnetization and decrease of coercivity reveal an association with the increase of oxygen vacancies induced by the doping of the Sm in the nanorods.

Niobium-substituted BiFeO 3( BiFe 1-x Nb x O 3 BFNO ) thin films were successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by spin coating with a sol–gel technology and rapid thermal annealing. The effects of Nb content (x = 0~0.08) on the microstructure, magnetic and multiferroic properties of thin films were investigated. The result of X-ray diffraction analysis shows that the BFNO thin films have rhombohedral (R3c) to tetragonal (P4mm) phase transition at x = 0.06. The Nb doping in the B-site of BiFeO 3 could induce the appearance of the spontaneous magnetization and polarization by the phase transition of rhombohedral-to-tetragonal. The BFNO thin films with x = 0.06 exhibits the maximum remanent magnetization (2Mr) of 5.2 emu/g.

La -doped and Cu -doped ZnO nanowires have been prepared to compare the substitution effect on the microstructural and magnetic properties. The XRD patterns of both compositions with single diffraction peak (002) show the same wurtzite hexagonal structure. The growth rate of the ZnO nanowires were enhanced by Cu doping, which were different from the suppression of growth rate by La doping. Room temperature ferromagnetism is observed for all ZnO , Cu -doped ZnO and La -doped ZnO nanowires. The saturation magnetizations are 0.102, 0.232 and 0.04 emu/g for ZnO , Cu -doped ZnO and La -doped ZnO nanowires, respectively. The results showed that the ferromagnetism is restrained by Cu doping, but enhanced by the La doping.

Lithium tantalite (LiTaO3) thin films (∼0.5 μm ) have been successfully deposited on Pt (111)/ SiO 2 / Si (1 0 0) substrates by means of sol–gel spin-coating technology. Figures of merit for infrared detector were studied for the LiTaO3 thin films. There exists high figures of merit Fv of 2.1×10 −10 C cm/J and Fm of 2.4×10 −8 C cm/J because of the relative low dielectric constant (er) of 35 and high pyroelectric coefficient (γ) of 4.0×10 −8 C/cm 2 K of the films. The pyroelectric infrared detector fabricated by the LiTaO3 thin film exhibits a voltage reponsivity Rv of 4584 V/W at 20 Hz and a high specific detectivity D ∗ of 4.23×10 7 cm Hz 1/2 / W at 100 Hz .

Aligned ZnO nanowires with different lengths (1 to approximately 4 μm) have been deposited on indium titanium oxide-coated glass substrates by using the solution phase deposition method for application as a work electrode in dye-sensitized solar cells (DSSC). From the results, the increases in length of zinc oxide (ZnO) nanowires can increase adsorption of the N3 dye through ZnO nanowires to improve the short-circuit photocurrent (Jsc) and open-circuit voltage (Voc), respectively. However, the Jsc and Voc values of DSSC with ZnO nanowires length of 4.0 μm (4.8 mA/cm2 and 0.58 V) are smaller than those of DSSC with ZnO nanowires length of 3.0 μm (5.6 mA/cm2 and 0.62 V). It could be due to the increased length of ZnO nanowires also resulted in a decrease in the transmittance of ZnO nanowires thus reducing the incident light intensity on the N3 dye. Optimum power conversion efficiency (η) of 1.49% was obtained in a DSSC with the ZnO nanowires length of 3 μm.

One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.