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1.
(Na0.85K0.15)0.5Bi0.5TiO3 thin films were deposited on LaNiO3(LNO)/SiO2/Si(1 0 0) and Pt/Ti/SiO2/Si(1 0 0) substrates by metal-organic decomposition, and the effects of bottom electrodes LNO and Pt on the ferroelectric, dielectric and piezoelectric properties were investigated by ferroelectric tester, impedance analyzer and scanning probe microscopy, respectively. For the thin films deposited on LNO and Pt electrodes, the remnant polarization 2Pr are about 22.6 and 8.8 μC/cm2 under 375 kV/cm, the dielectric constants 238 and 579 at 10 kHz, the dielectric losses 0.06 and 0.30 at 10 kHz, the statistic d33eff values 95 and 81 pm/V. The improved piezoelectric properties could make (Na1−xKx)0.5Bi0.5TiO3 thin film as a promising candidate for piezoelectric thin film devices. 相似文献
2.
Thin film of both A- and B-site co-substituted Sr0.8Bi2.2Ta2O9 (SBT) by Pr3+ and Nb5+, i.e. Sr0.8Pr0.1Bi2.1Ta1.5Nb0.5O9 (SPBTN) was fabricated on Pt/Ti/SiO2/Si substrates by metalorganic decomposition method. The Nb5+ substitution at B-site and Pr3+ substitution at A-site enhanced the remanent polarization and reduced the coercive field of the films, respectively. The remanent polarization (2Pr) value of the SPBTN film was 22 μC/cm2. The coercive field (2Ec) value of the SPBTN film was 102 kV/cm, which was much lower than that of SBTN (165 kV/cm). The effects of substitution on structural and ferroelectric properties of SBT were discussed in detail. As a result, the A- and B-sites co-substitution may be one of the promising ways to improve ferroelectric properties of SBT. 相似文献
3.
Vincent Maurice 《Surface science》2005,581(1):88-104
STM, STS, LEED and XPS data for crystalline θ-Al2O3 and non-crystalline Al2O3 ultra-thin films grown on NiAl(0 0 1) at 1025 K and exposed to water vapour at low pressure (1 × 10−7-1 × 10−5 mbar) and room temperature are reported. Water dissociation is observed at low pressure. This reactivity is assigned to the presence of a high density of coordinatively unsaturated cationic sites at the surface of the oxide film. The hydroxyl/hydroxide groups cannot be directly identify by their XPS binding energy, which is interpreted as resulting from the high BE positions of the oxide anions (O1s signal at 532.5-532.8 eV). However the XPS intensities give evidence of an uptake of oxygen accompanied by an increase of the surface coverage by Al3+ cations, and a decrease of the concentration in metallic Al at the alloy interface. A value of ∼2 for the oxygen to aluminium ions surface concentration ratio indicates the formation of an oxy-hydroxide (AlOxOHy with x + y ∼ 2) hydroxylation product. STM and LEED show the amorphisation and roughening of the oxide film. At P(H2O) = 1 × 10−7 mbar, only the surface of the oxide film is modified, with formation of nodules of ∼2 nm lateral size covering homogeneously the surface. STS shows that essentially the valence band is modified with an increase of the density of states at the band edge. With increasing pressure, hydroxylation is amplified, leading to an increased coverage of the alloy by oxy-hydroxide products and to the formation of larger nodules (∼7 nm) of amorphous oxy-hydroxide. Roughening and loss of the nanostructure indicate a propagation of the reaction that modifies the bulk structure of the oxide film. Amorphisation can be reverted to crystallization by annealing under UHV at 1025 K when the surface of the oxide film has been modified, but not when the bulk structure has been modified. 相似文献
4.
M.S. Chen 《Surface science》2007,601(3):632-637
The growth of Au on an ultra-thin, ordered Mo(1 1 2)-(8 × 2)-TiOx, was investigated using scanning tunneling microscopy (STM), low energy ion scattering spectroscopy (LEISS), X-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD). Wetting of the TiOx surface by Au was observed with STM and LEISS, and the ordering of the Au films was atomically resolved with STM. TPD showed that Au binds more strongly to the reduced TiOx film than to bulk TiO2, but more weakly than to the Mo substrate. The Au-TiOx binding energy is greater than Au-Au in bulk Au. The oxidation state of Ti in the TiOx film was deduced by XPS and from the Ti-O phonon shifts relative to bulk TiO2. The TiOx/Mo(1 1 2) film structure and those for the (1 × 1)- and (1 × 3)-Au/TiOx/Mo(1 1 2) surfaces are discussed. 相似文献
5.
X.L. Zhong 《Applied Surface Science》2006,253(2):417-420
Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated on Pt/Ti/SiO2/Si(1 0 0) substrates by chemical solution deposition (CSD), and the dependence of ferroelectric and dielectric properties of the as-deposited BLT thin films on excess Bi content in precursor sols was studied. It is found that the prepared BLT thin film shows the best polarization-electric field, capacitance-voltage and dielectric constant (?r)-frequency characteristics, when the value of excess Bi content in precursor sols is 10%. In detail, its remnant polarization (2Pr) value is 40 μC/cm2, the capacitance tunability is 21% measured at room temperature under conditions of an applied voltage of 8 V and measurement frequency of 10 kHz, and the ?r is 696 at 100 kHz frequency. 相似文献
6.
The fully-oxidized surface that forms on (1 1 1) oriented Ni3Al single crystals, with and without Pt addition, at 300-900 K under oxygen pressures of ca. 10−7 Torr was studied using XPS, AES, and LEIS. Two main types of surfaces form, depending upon oxidation temperature. At low-temperature, the predominant oxide is NiO, capped by a thin layer of aluminum oxide, which we refer to generically as AlxOy. At high-temperature (i.e., 700-800 K), NiO is replaced by a thick layer of AlxOy. By comparing samples that contain 0, 10 and 20 at.% Pt in the bulk, we find that the effect of Pt is to: (1) reduce the maximum amount of both NiO and AlxOy; and (2) shift the establishment of the thick AlxOy layer to lower temperatures. Platinum also decreases the adsorption probability of oxygen on the clean surface. 相似文献
7.
Poly(3-methylthiophene) (P3MT)-based porous silicon (PS) substrates were fabricated and characterized by cyclic voltammetry, scanning electron microscopy, and auger electron spectroscopy. After doping urease (Urs) into the polymeric matrix, sensitivity and physicochemical properties of the P3MT-based PS substrate was investigated compared to planar silicon (PLS) and bulk Pt substrates. PS substrate was formed by electrochemical anodization in an etching solution composed of HF, H2O, and ethanol. Subsequently, Ti and Pt thin-films were sputtered on the PS substrate. Effective working electrode area (Aeff) of the Pt-deposited PS substrate was determined from a redox reaction of Fe(CN)63−/Fe(CN)64− redox couple in which nearly reversible cyclic voltammograms were obtained. The ip versus v1/2 plots showed that Aeff of the PS-based Pt thin-film electrode was 1.62 times larger than that of the PLS-based electrode.Electropolymerization of P3MT on both types of electrodes were carried out by the anodic potential scanning under the given potential range. And then, urease molecules were doped to the P3MT film by the chronoamperometry. Direct electrochemistry of a Urs/P3MT/Pt/Ti/PS electrode in an acetonitrile solution containing 0.1 mol/L NaClO4 was introduced compared to a P3MT/Pt/Ti/PS electrode at scan rates of 10 mV s−1, 50 mV s−1, and 100 mV s−1.Amperometric sensitivity of the Urs/P3MT/Pt/Ti/PS electrode was ca. 1.67 μA mM−1 per projected unit square centimeter, and that of the Urs/P3MT/Pt/Ti/PLS electrode was ca. 1.02 μA mM−1 per projected unit square centimeter in a linear range of 1-100 mM urea concentrations. 1.6 times of sensitivity increase was coincident with the results from cyclic voltammetrc analysis.Surface morphology from scanning electron microscopy (SEM) images of Pt-deposited PS electrodes before and after the coating of Urs-doped P3MT films showed that pore diameter and depth were 2 μm and 10 μm, respectively. Multilayered-film structures composed of metals and organics for both electrodes were also confirmed by auger electron spectroscopy (AES) depth profiles. 相似文献
8.
Ba0.6Sr0.4TiO3 thin films were deposited on Pt/SiO2/Si substrate by radio frequency magnetron sputtering. High-resolution transmission electron microscopy (HRTEM) observation shows that there is a transition layer at BST/Pt interface, and the layer is about 7-8 nm thickness. It is found that the transition layer was diminished to about 2-3 nm thickness by reducing the initial RF sputtering power. X-ray photoelectron spectroscopy (XPS) depth profiles show that high Ti atomic concentration results in a thick interfacial transition layer. Moreover, the symmetry ν of ?r-V curve of BST thin film is enhanced from 52.37 to 95.98%. Meanwhile, the tunability, difference of negative and positive remanent polarization (Pr), and that of coercive field (EC) are remarkably improved. 相似文献
9.
Zuci Quan 《Applied Surface Science》2010,256(11):3669-3675
Zn0.95−xCo0.05CuxO (ZCCO, where x = 0, 0.005, 0.01 and 0.015) thin films were deposited on Si (1 0 0) substrates by pulsed laser deposition technique. Crystal structures, surface morphologies, chemical compositions, bonding states and chemical valences of the corresponding elements for ZCCO films were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and X-ray photoelectron spectroscopy (XPS). XRD and FESEM results indicate that crystallite sizes of the highly (0 0 2)-oriented ZCCO films slightly decrease with increasing Cu content. When the Cu content increases from 0 to 0.015, Zn 2p3/2, Co 2p, Cu 2p3/2 and O 1s peaks of the ZCCO film shift towards higher or lower binding energy regions, and the reasons for these chemical shifts are investigated by fitting the corresponding XPS narrow-scan spectra. Both in-plane and out-of-plane magnetization-magnetic field hysteresis loops of the ZCCO films reveal that all the films have room temperature ferromagnetisms (RTFMs). The conceivable origin of the RTFM is ascribed to the combined effects of the local structural disorder resulted from (Co2+, Cu2+, Cu1+)-cations which substitute Zn2+ ions in the ZnO matrices, ferromagnetic coupling between coupled dopant atoms caused by Co2+ (3d74s0) and Cu2+ (3d94s0) spin states, and exchange interactions between the unpaired electron spins originating from lattice defects induced by Cu doping in the Zn0.95Co0.05O matrices. 相似文献
10.
Jiagang Wu Jiliang Zhu Dingquan Xiao Jianguo Zhu Junzhe Tan Qinglei Zhang Yuanyu Wang 《Applied Surface Science》2007,253(14):6222-6225
(Pb0.95Ca0.05)(Nb0.02Zr0.80Ti0.20)O3 [PCNZT] thin films were deposited on the Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by RF magnetron sputtering with and without a LaNiO3 [LNO] buffer layer. Ca and Nb elements in PZT films enhance the ferroelectric property, LaNiO3 buffer layer improves the crystal quality of the PCNZT thin films. PCNZT thin films possess better ferroelectric property than that of PZT films for Ca and Nb ion substitution, moreover, PCNZT thin films with a LNO buffer layer possess (1 0 0) orientation and good ferroelectric properties with high remnant polarization (Pr = 38.1 μC/cm2), and low coercive field (Ec = 65 kV/cm), which is also better than that of PCNZT thin films without a LNO buffer layer (Pr = 27.9 μC/cm2, Ec = 74 kV/cm). The result shows that enhanced ferroelectric property of PZT films can be obtained by ion substitution and buffer layer. 相似文献
11.
Shufang Wang Jinchun Cheng Songqing Zhao Mingjing Chen Jianglong Wang 《Applied Surface Science》2010,257(1):157-159
We report the laser-induced voltage (LIV) effects in c-axis oriented Bi2Sr2Co2Oy thin films grown on (0 0 1) LaAlO3 substrates with the title angle α of 0°, 3°, 5° and 10° by a simple chemical solution deposition method. A large open-circuit voltage with the sensitivity of 300 mV/mJ is observed for the film on 10° tilting LaAlO3 under a 308 nm irradiation with the pulse duration of 25 ns. When the film surface is irradiated by a 355 nm pulsed laser of 25 ps duration, a fast response with the rise time of 700 ps and the full width at half maximum of 1.5 ns is achieved. In addition, the experimental results reveal that the amplitude of the voltage signal is approximately proportional to sin 2α and the signal polarity is reversed when the film is irradiated from the substrate side rather than the film side, which suggests the LIV effects in Bi2Sr2Co2Oy thin films originate from the anisotropic Seebeck coefficient of this material. 相似文献
12.
Influence of both substrate temperature, Ts, and annealing temperature, Ta, on the structural, electrical and microstructural properties of sputtered deposited Pt thin films have been investigated. X-ray diffraction results show that as deposited Pt films (Ts = 300, 400 °C) are preferentially oriented along (1 1 1) direction. A little growth both along (2 0 0) and (3 1 1) directions are also noticed in the as deposited Pt films. After annealing in air (Ta = 500-700 °C), films become strongly oriented along (1 1 1) plane. With annealing temperature, average crystallite size, D, of the Pt films increases and micro-strain, e, and lattice constant, a0, decreases. Residual strain observed in the as deposited Pt films is found to be compressive in nature while that in the annealed films is tensile. This change in the strain from compressive to tensile upon annealing is explained in the light of mismatch between the thermal expansion coefficients of the film material and substrate. Room temperature resistivity of Pt films is dependant on both the Ts and Ta of the films. Observed decrease in the film resistivity with Ta is discussed in terms of annihilation of film defects and grain-boundary. Scanning electron microscopic study reveals that as the annealing temperature increases film densification improves. But at an annealing temperature of ∼600 °C, pinholes appear on the film surface and the size of pinhole increases with further increase in the annealing temperature. From X-ray photoelectron spectroscopic analysis, existence of a thin layer of chemisorbed atomic oxygen is detected on the surfaces of the as deposited Pt films. Upon annealing, coverage of this surface oxygen increases. 相似文献
13.
Bi1.5Zn1.0Nb1.5O7/Ba0.6Sr0.4TiO3/Bi1.5Zn1.0Nb1.5O7 tunable multilayer thin film has been fabricated by pulsed laser ablation and characterized. Phase composition and microstructure of multilayer films were characterized by X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The film has very smooth surface with RMS roughness of 1.5-2 nm and grain size of 100-150 nm. Total film thickness has been measure to be 375 nm. The BZN thin films at 300 K, on Pt(1 1 1)/SiO2/Si substrate showed zero-field dielectric constant of 105 and dielectric loss tangent of 0.002 at frequency of 0.1 MHz. Thin films annealed at 700 °C shows the dielectric tunability of 18% with biasing field 500 kV/cm at 0.1 MHz. The multilayer thin film shows nonferroelectric behavior at room temperature. The good physical and electrical properties of multilayer thin films make them promising candidate for tunable microwave device applications. 相似文献
14.
La-substituted BiFeO3, Bi0.8La0.2FeO3, thin films were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. X-ray diffraction and high-resolution transmission electron microscope were used to analyze the structures of the films. The results show the films fabricated under optimized growth condition are (0 1 2) textured. X-ray photoemission spectroscopy results indicate that the oxidation state of Fe ion is Fe3+ in the films without detectable Fe2+. The films show low leakage current and excellent dielectric characters. Multiferroic properties with a remnant ferroelectric polarization of 5.2 μC/cm2 and a remanent magnetization of 0.02 μB/Fe were established. These results have some implications for further research. 相似文献
15.
Xiaohua Zhang Peng Shi Aifeng Tian Hong Xin Xiaofeng Chen Xiaoqing Wu Xi Yao 《Applied Surface Science》2010,256(22):6607-9306
The influence of substrate temperature on structural and dielectric properties of cubic pyrochlore Bi1.5Zn1.0Nb1.5O7 (BZN) thin films prepared by pulsed laser deposition process has been investigated. BZN thin films were deposited on Pt/Ti/SiO2/Si(1 0 0) substrate and in situ annealed at 700 °C. The results indicate that the substrate temperature has a significant effect on the structural and dielectric properties of BZN thin films. The films exhibit a cubic pyrochlore structure in the substrate temperature range from 550 °C to 700 °C and at the annealing temperature of 700 °C. With further increase of substrate temperature to 750 °C, the phases of Bi2O3, BiNbO4 and Bi5Nb3O15 can be detected in the XRD pattern due to the Zn loss. The dielectric constant and loss tangent of the films deposited at 650 °C are 192 and 6 × 10−4 at 10 kHz, respectively. The tunability is 10% at a dc bias field of 0.9 MV/cm. 相似文献
16.
XPS and LEED have been used to characterize the interaction of sputter-deposited Pt (maximum coverage <5 ML) with Nb-doped SrTiO3(0 0 1) surfaces prepared either by annealing in O2 and then UHV, or by chemical-etching in aqua regia. The annealed surface exhibits an ordered (1 × 1) LEED pattern, with additional diffraction spots and streaks indicating the presence of oxygen vacancies. Increasing Pt coverage results in the decrease of the observed Pt(4f7/2) binding energy and the uniform shift of the Sr(3d), Ti(2p) and O(1s) levels to smaller binding energies, as expected for Pt cluster growth and surface-to-Pt charge donation on an n-type semiconductor. The etched surface is disordered, and exhibits a hydroxylated surface with a contaminant C film of ∼23 ? average thickness. Pt deposition on the etched surface results in an immediate decrease in the intensity of the OH feature in the O(1s) spectrum, and a uniform shift of the Sr(3d), Ti(2p) and O(1s) levels to larger binding energies with increasing Pt coverage. The observed Pt(4f7/2) binding energy on the etched surface (∼72 eV) is independent of Pt coverage, and indicates substantial electronic charge donation from the Pt to surface hydroxyl species. The observation of band bending towards higher binding energies upon Pt deposition (behavior normally associated with p-type semiconductors) demonstrates that sub-monolayer quantities of adsorbates can alter metal/oxide interfacial charge transfer and reverse the direction of band bending, with important consequences for Schottky barrier heights and device applications. 相似文献
17.
L. Cui 《Physica B: Condensed Matter》2009,404(1):150-153
Sr2Bi4Ti5O18 (SBTi) and Nd-modified SBTi (SBNT) thin films were deposited on Pt/Ti/SiO2/Si (1 0 0) substrates using a sol-gel method. Structure, morphology and electric properties were investigated systematically. These films were randomly oriented and composed of rod-like grains. The remanent polarization (2Pr) and coercive field (Ec) of SBNT films were 30 μC/cm2 and 55 kV/cm, respectively. This value of 2Pr was much higher than the reported value of SBTi prepared by pulsed-laser deposition. More importantly, the SBNT films showed high fatigue resistance against continuous switching up to 3×109 cycles and excellent charge-retaining ability up to 3×104 s. 相似文献
18.
Effects of lanthanum (La) substitution (0.003 ≤ x ≤ 0.015) on the dielectric and ferroelectric properties of Pb(Zr0.5Ti0.5)O3 thin films have been investigated. The films were synthesized on the Pt (1 1 1)/Ti/SiO2/Si (1 0 0) substrates by a sol-gel method. Large dielectric constants of the films are obtained within range of 800-1600 which are almost comparable to those observed in bulk ceramics. The films also show improved remnant polarization values and reduced coercive field values with the increasing addition of La substitution. Our results suggest that low La substitution contributes to enhance film electric properties due to the improvement of non-180° domain wall mobility as well as the stabilization of tetragonal phase. 相似文献
19.
Using the lyotropic liquid crystalline templating strategy, the nanostructured platinum film was electrochemically deposited on the α-Al2O3 supported dense palladium membrane. The XRD and TEM results of the Pt film revealed a hexagonal array of cylindrical pores with a uniform pore diameter of ca. 3.8 nm and a pore-to-pore separation of ca. 7.6 nm. The structure parameters of the Pt film were almost the same as those of the hexagonal liquid crystalline template. Based on SEM observations, the Pt film was featureless, smooth, and tightly adherent to the dense Pd membrane. The specific surface area of the Pt film, measured by using cyclic voltammetry, was ca. 13.8 m2 g−1, which was in accord with the theoretical value of 14.5 m2 g−1 for a perfect hexagonal nanostructure with the same structure parameters. By combining the dense Pd membrane for selective permeation to hydrogen with the Pt film of high specific surface area for catalysis, the as-synthesized two-layer film will be a promising catalytic membrane to intensify hydrogen-related reaction processes. 相似文献
20.
Ba(Zr0.05Ti0.95)O3 (BZT) thin films grown on Pt/Ti/SiO2/Si(1 0 0) substrates were prepared by chemical solution deposition. The structural and surface morphology of BZT thin films has been studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the random oriented BZT thin film grown on Pt/Ti/SiO2/Si(1 0 0) substrate with a perovskite phase. The SEM surface image showed that the BZT thin film was crack-free. And the average grain size and thickness of the BZT film are 35 and 400 nm, respectively. Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. The XPS results show that Ba, Ti, and Zr exist mainly in the forms of BZT perovskite structure. 相似文献