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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.

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.

TransparentZn1-xMgxO(x=0.01, 0.03, and 0.05) nanocrystalline films were prepared by sol-gel method followed by thermal annealing treatment of 700°C. Mg doping effect on the microstructural and optical properties of theZn1-xMgxOfilms is investigated. From SEM images of all films, mean sizes of uniform spherical grains increase progressively. Pure wurtzite structure is obtained from the results of XRD. Grain sizes increase from 34.7 nm forx=0.01and 37.9 nm forx=0.03to 42.1 nm forx=0.05deduced from the XRD patterns. The photoluminescence spectra of the films show a strong ultraviolet emission and a weak visible light emission peak. The enhancement of ultraviolet emission and reduction of visible emission are observed due to the increase of Mg doping concentration and the corresponding decrease of oxygen vacancy defects. Besides, the characteristics of the dark/photo currents withn-Zn1-xMgxO/n-Siheterojunction are studied for photodetector application.

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.

Four p–i–n GaInP solar cells were grown by metal organic chemical vapor deposition (MOCVD) with different intrinsic layer thicknesses from 0.25 to 1 µm. A series of optical measurements, including electroreflectance (ER), photoluminescence (PL), electric luminescence (EL), and photocurrent (PC) measurements, have been performed to study the built-in electric field effect and to determine the suitable thickness of an intrinsic layer. The PL and EL spectra reflected the crystal quality of the GaInP layers. Furthermore, from the obtained ER spectrum, the built-in electric field in the intrinsic layer can be revealed. From the PC spectra under various bias voltages, the effect of built-in electric fields on the collection of photogenerated carriers has been studied.

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.

Bi1-xPrxFe0.95Mn0.05O3 (BPFMO) 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 Pr content on the microstructure, magnetic and multiferroic properties of thin films were investigated. The result of X-ray diffraction analysis shows that the BPFMO thin films have rhombohedral-to-tetragonal R3c→P4mm phase transition at x = 0.15. The Pr doping on the A-site of BiFeO3 could induce the appearance of the spontaneous magnetization and polarization by the phase transition of rhombohedral-to-tetragonal. The BPFMO thin films with x = 0.2 exhibits the maximum remanent magnetization (2Mr) of 0.44 emu/g.

Well-defined ZnO and ZnO: La 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 ZnO: La nanorods observed by FE-SEM is smaller than that of pure ZnO indicating the inhibition of growth rate by the doping of La. Photoluminescence spectra show an enhancement of the luminescence intensity in green-yellow region by the dopant La. Ferromagnetism is observed from the results of magnetization measurement. The increase of the saturation magnetization reveals an association with the increase of oxygen vacancies induced by the doping of the La in the nanorods.

Bi 4 Ti 2.96 Ta 0.04 O 12 (BTTO) thin films were deposited on Pt(111)/Ti/SiO 2 /Si(100) substrates by sol–gel method. The effects of Ta-substitution and annealing temperature (500–800 °C) on the microstructure and ferroelectric properties of Bi 4 Ti 3 O 12 thin films were investigated. X-Ray diffraction analysis reveals that the intensities of (117) peaks are realitively 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 BTTO thin films increases. The BTTO thin films annealed at 700 °C exhibit the highest remanent polarization (2P r ) of 40 μC/cm2 and lowest coercive field (2E c ) of 120 kV/cm. It is obvious that the measured 2P r of the BTTO thin film is larger than that of Bi 4 Ti 3 O 12 thin films (2P r =25 μC/cm2) The improved ferroelectric properties can be attributed to the substitution of Ta5+ to Ti4+ in Bi 4 Ti 3 O 12 assisted the elimination of defects such as oxygen vacancy and vacancy complexes.

Ferroelectric polymer/ceramic structure thin films were fabricated on Pt/SiO/sub 2//Si substrates using a sol-gel method. The bilayer thin film was composed of polar /spl beta/-phase poly(vinylidene fluoride) (PVDF) and 1 /spl mu/m thickness of polycrystalline lead titanate (PbTiO/sub 3/) thin film. By changing the concentrations of PVDF solutions (0.6/spl sim/1.0 M), various thickness of PVDF thin films (50-580 nm) were obtained, and the effects of various processing parameters on the characteristics of PVDF/PbTiO/sub 3/ thin films were studied. The characteristic of the /spl beta/ phase at infrared spectrum of 511 and 840 cm/sup -1/ can be observed in PVDF film crystallized at 65/spl deg/C for 2 h. With the increase of the PVDF thickness of the PVDF/PbTiO/sub 3/ films, the relative dielectric constant (/spl epsi//sub r/) decreased from 63 to 20 and the leakage current density (J) also decreased from 1.54 /spl times/ 10/sup -6/ to 3.86 /spl times/ 10/sup -7/ A/cm/sup 2/.

The novel pyroelectric infrared (IR) detectors have been fabricated using the Polyvinylidene Fluoride (PVDF)/Lead Titanate (PT) pyroelectric bilayer thin films which were deposited onto Pt(111)/SiO/sub 2//Si(100) substrates by a sol-gel process. The ceramic/polymer structure was constructed of the randomly oriented polycrystalline PT film(/spl sim/1 /spl mu/m) heated at 700/spl deg/C for 1 h and the /spl beta/-phase PVDF film crystallized at 65/spl deg/C for 2 h. The effects of PVDF thin film thickness (100/spl sim/580 nm) on the pyroelectric response of IR detectors were studied. The results show that the depositions of PVDF thin films onto the PT films will cause the leakage current (J) of the detectors decrease from 6.37 /spl times/ 10/sup -7/ A/cm/sup 2/ to 3.86 /spl times/ 10/sup -7/ A/cm/sup 2/. The specific detectivity (D*) measured at 100 Hz decreased from 2.72 /spl times/ 10/sup -7/ cm/spl middot/Hz/sup 1/2//W for detector without PVDF to 1.71 /spl times/ 10/sup -7/ cm/spl middot/Hz/sup 1/2//W for detector with PVDF thickness of 580 nm. By optimizing the ratio of the specific detectivity (D*) to leakage current, D*/J, the detector with PVDF thickness of 295 nm exhibits the best performance.

La-modified lead titanate (PLT) thin films were deposited on Pt/SiO/sub 2//Si substrates by spin coating with sol-gel processing. 1,3-propandiol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of high quality thin film. The randomly oriented PLT thin film exhibits a relatively small dielectric constant and a large pyroelectric coefficient without poling treatment. Pyroelectric infrared (IR) detectors have been fabricated without the back side etching process The pyroelectric characteristics of point detectors with various La contents as a function of modulation frequency are compared. It was found that the PLT(10) detector has a large voltage responsivity of 3330 (V/W) at 20 Hz. The specific detectivity (D*) at 100 Hz is 6.2/spl times/10/sup 7/ cmHz/sup / 1/2 //W. The results showed that Pb/sub 1-x/La/sub x/Ti/sub 1-x/4/O/sub 3/ thin film with x=0.10 [PLT(10)] was most suitable for use as a pyroelectric IR detector.

Calcium-modified lead titanate (PCT) thin film pyroelectric infrared (IR) detectors were fabricated on Pt(111)/SiO/sub 2//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 /spl times/ 10/sup 7/ cmHz/sup 1/2//W at 100 Hz The results show that Pb/sub 1-x/Ca/sub x/TiO/sub 3/ thin film with x = 0.25 [PCT(25)] was most suitable for application to the pyroelectric thin film IR detector.

Polycrystalline thin films of Mg-modified lead titanate (PMT) were deposited on Pt/SiO2/Si substrates using a diol-based sol-gel process. 1,3-propanediol was used as solvent to minimize the number of cycles of spin coating and drying processes to obtain the desired thickness of high quality thin film. By changing the Mg content (2 to approximately 8 mol%) and heating temperature (500 to approximately 800 degrees Celsius), the influences of various processing parameters on the characteristics of thin films were studied. With the increase of the Mg content, the relative dielectric constant ((epsilon) r) of PMT thin film increased from 39 to 91 at the heating temperature of 700 degrees Celsius. It was found that the coercive field (Ec) and the remanent polarization (Pr) decreased, but the pyroelectric coefficient (gamma) increased with an increase of Mg content. The results reveal that PMT thin film with a Mg content of 6 mol% exhibits the largest figures of merit for the voltage responsivity and the specific detectivity at a heating temperature of 700 degrees Celsius.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

High-performance pyroelectric infrared (IR) detectors have been fabricated without the back side etching process usingMg-modified lead titanate (Pb1MgTiO3) thin films. PMT thin films were deposited on (1 1 1)-oriented Pt thin film onSi02/Si(100) substrates by a diol-based sol-gel process. The randomly oriented PMT thin film exhibits a relatively small di-electric constant and a large pyroelectric coefficient without poling treatment. The pyroelectric characteristics of point de-tectors with various Mg contents as a function of modulation frequency are compared. It was found that the PMT(6) thinfilm detector has a large voltage responsivity of 5280 (V/W) at 20 Hz. The specific detectivity (D*) at 100 Hz is 5. 12x iO cmHz"2/W. The results showed that Pb1MgTiO3 thin film with x0.06 [PMT(6)] was most suitable for use as a pyroelectric IR detector.Keywords: sol-gel, PMT, pyroelectric, JR detector, voltage responsivity, specific detectivity 1. INTRODUCTION Pyroelectric detectors are an important class of thermal transducers, which are based on the temperature-induced spon-taneous polarization change exhibited by certain crystals. Researches on ferroelectric materials for the pyroelectric detectionof infrared (IR) radiation have become an attractive technological activity in the last few years. 1-8.

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.

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.

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.

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%.

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.

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.

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.