Synthesis and characterization of Gd0.1Ce0.9O1.95 thin films by spray pyrolysis technique

The Gd doped ceria (CGO) in thin layers is of great interest for low temperature operation. In the present investigation, we report on the use of spray pyrolysis technique for the synthesis of CGO thin films. The process parameters were optimized for synthesizing Gd_0.1Ce_0.9O_1.95 films. Films were characterized by XRD, EDS, SEM, and AFM and are observed to be phase pure and dense with surface roughness of the order of ∼5 nm. The d.c. conductivity was also measured and is observed to be ∼0.5 S/cm at 623 K.     

Microstructural characterization of La0.4Sr0.6Co0.8Fe0.2O3-δ films deposited by dip coating

The dip-coating method has been successfully used for depositing porous electrodes of La_0.4Sr_0.6Co_0.8Fe_0.2O_3-δ (LSCF) films. Perovskite oxide cobaltites powders have been prepared by an acetic acid-based gel route. Then, cathode films were deposited onto ceramic substrates of the usual electrolyte Cerium Gadolinium Oxide (CGO) by dip coating. The structure and morphology of the powders and films were characterized by X-ray, diffraction (XRD) and scanning electron microscopy (SEM) respectively, to study the correlation between microstructure and deposition parameters. Optimum parameters for obtaining continuous, homogeneous and crack free LSCF films were determined.     

Si基铁电Bi3.15Nd0.85Ti3O12多层薄膜的一致取向生长和性能的研究

采用脉冲激光沉积(PLD)技术，利用LSCO/CeO₂/YSZ多异质缓冲层，在Si(100)基 片上成功地制备了c轴一致取向的Bi_3.15Nd_0.85Ti₃O12(BNT)铁电薄膜.利用X射线衍射(XRD)和扫描电镜(SEM)分析测定了薄膜的相结构 、取向和形貌特征，考察了沉积温度和氧分压对BNT薄膜微结构、取向和形貌的影响，确定 了BNT薄膜的最佳沉积条件.对在优化的条件下制备得到的BNT薄膜的C-V曲线测试得到了典型 的蝴蝶形曲线，表明该薄膜具有较好的电极化反转存储特性.最后讨论了BNT薄膜铁电性能与 薄膜取向的相关性. 关键词： 3.15Nd_0.85Ti₃O₁₂')" href="#">Bi_3.15Nd_0.85Ti₃O₁₂ 铁电薄 膜 多层异质结 脉冲激光沉积     

Electrical behavior of BaZr0.1Ti0.9O3 and BaZr0.2Ti0.8O3 thin films

BaZr_0.1Ti_0.9O₃ and BaZr_0.2Ti_0.8O₃ (BZT) thin films were deposited on Pt/Ti/LaAlO₃ (1 0 0) substrates by radio-frequency magnetron sputtering, respectively. The films were further annealed at 800 °C for 30 min in oxygen. X-ray diffraction θ-2θ and Φ-scans showed that BaZr_0.1Ti_0.9O₃ films displayed a highly (h 0 0) preferred orientation and a good cube-on-cube epitaxial growth on the LaAlO₃ (1 0 0) substrate, while there are no obvious preferential orientation in BaZr_0.2Ti_0.8O₃ thin films. The BaZr_0.1Ti_0.9O₃ films possess larger grain size, higher dielectric constant, larger tunability, larger remanent polarization and coercive electric field than that of BaZr_0.2Ti_0.8O₃ films. Whereas, BaZr_0.1Ti_0.9O₃ films have larger dielectric losses and leakage current density. The results suggest that Zr⁴⁺ ion can decrease dielectric constant and restrain non-linearity. Moreover, the enhancement in dielectric properties of BaZr_0.1Ti_0.9O₃ films may be attributed to (1 0 0) preferred orientation.     

Spray pyrolytic deposition of solid electrolyte Bi2V0.9Cu0.1O5.35 films

Copper substituted bismuth vanadate films have been successfully deposited first time by spray pyrolysis technique on glass substrates suitable for low temperature solid oxide fuel cells. Desired phase formation of polycrystalline Bi₂V_0.9Cu_0.1O_5.35 (BICUVOX.10) was confirmed by X-ray diffraction technique. These films were further studied with EDAX and SEM techniques for their compositional and morphological characterization. Electrical conductivity of BICUVOX.10 is found to be 5.7 × 10⁻² (Ω cm)⁻¹ at 698 K, predicts the onset temperature for ionic contribution suitable for low temperature SOFC applications. Room temperature complex impedance plot reveals that electrical process arises due to contribution from the grain interior.     

Optical and thermoelectric characterizations of electroplated n-Bi2(Te0.9Se0.1)3

Bismuth selenotelluride (Bi₂(Te_0.9Se_0.1)₃) films were electrodeposited at constant current density from acidic aqueous solutions with Arabic gum in order to produce thin films for miniaturized thermoelectric devices. X-ray fluorescence spectroscopy determined film compositions. X-ray diffraction pattern shows that the films as deposited are polycrystalline, isostructural to Bi₂Te₃ and covered by crystallites. Mueller-matrix analysis reveals that the electroplated layers are optically like an isotropic medium. Their pseudo-dielectric functions were determined using mid-infrared spectroscopic ellipsometry. Tauc-Lorentz combined with Drude dispersion relations were successfully used. The energy band gap E_g was found to be about 0.15 eV. Moreover, the fundamental absorption edge was described by an indirect optical band-to-band transition. From Seebeck coefficient measurement, films exhibit n-type charge carrier and the value of thermoelectric power is about −40 μV/K.     

Epitaxial thin films of (Bi0.9La0.1)2NiMnO6 obtained by pulsed laser deposition

Bulk Bi₂NiMnO₆ has been shown to be ferromagnetic and ferroelectric. Here, we report a systematic study of the influence of the deposition conditions on the growth of (Bi_0.9La_0.1)₂NiMnO₆ thin films onto (0 0 1) SrTiO₃ substrates by pulsed laser deposition. Oxygen pressure and substrate temperature have been varied from 0.3 to 0.6 mbar and 600 to 660 °C, respectively. Whereas it is found that single-phase and epitaxial films can be obtained in a relatively broad oxygen pressure range, the temperature window, centred on 620 °C, is extremely narrow. Films of low roughness, about 1 unit cell, have been obtained. It is found that the magnetisation of the films, which are ferromagnetic with Curie temperatures about 100 K, is lower than the expected theoretical value, which might be attributed to an incomplete Ni-O-Mn long-range ordering.     

Microstructure and electrical properties of Ba0.5Sr0.5TiO3 thin films prepared on copper foils with La2O3 buffer layers

Ba_0.5Sr_0.5TiO₃ (BST) thin films were deposited on copper foils via sol-gel method with La₂O₃ as a buffer layer. The films were processed in almost inert atmosphere so that the substrate oxidation was avoided while allowing the perovskite film phase to crystallize. The existence of a La₂O₃ buffer layer between the BST thin film and Cu foil improved the dielectric constant and reduced the leakage current density of the BST thin film. Meanwhile, the BST thin film exhibited ferroelectric character at room temperature, which was contrast to the para-electric behavior of the film without the buffer layer. Effects of La₂O₃ buffer layer on the crystallizability and microstructure of BST thin films were also investigated.     

巨磁电阻材料La0.9Sr0.1MnO3与半导体Si组成的二极管的整流特性

掺杂锰氧化物La_0.9Sr_0.1MnO₃薄膜被直接沉积在n型 硅基片上，构成p-n结.这种p-n结在很宽的温度范围内都有很好的整流特性.研究结果表明， 这种p-n结的结电阻对低磁场敏感，在3×10^-2T的磁场下，磁电阻可达70％.磁 电阻的正负依赖于温度.磁电阻的大小可通过加在p-n结上的电压调节.     

Optical and electronic properties of NiFe2O4 and CoFe2O4 thin films

We report the optical and electronic properties of the inverse spinel ferrite NiFe₂O₄ and CoFe₂O₄ thin films deposited on single crystal sapphire by electron beam deposition. We carried out variable temperature (78–500 K) transmittance measurements on the thin films to investigate the optical properties and electronic structures of these ferrites. The absorption spectra of both NiFe₂O₄ and CoFe₂O₄ thin films show insulating characters with Ni (Co) d to d on-site transitions below 3 eV. The energy bands above 3 eV are mainly due to the O 2p to Fe 3d charge transfer transitions. The observed electronic transitions have been assigned based on the first principles calculations and comparisons with structurally similar Ni and Co-containing compounds. The Co²⁺ d to d transition in the CoFe₂O₄ thin film shows a strong temperature dependence, likely due to the spin-charge coupling effect.     

Effects of deposition parameters on laser-induced damage threshold of Ta2O5 films

Ta₂O₅ films were deposited on BK7 substrates by e-beam evaporation with different deposition parameters such as substrate temperature (323-623 K), oxygen pressure (0.5-3.0×10⁻² Pa) and deposition rate (0.2-0.5 nm/s). Absorption, scattering and chemical composition were investigated by surface thermal lensing (STL) technique, total integrated scattering (TIS) measurement and X-ray photoelectron spectroscopy (XPS), respectively. The laser-induced damage threshold (LIDT) was assessed using pulsed Nd:YAG 1064 nm laser at a pulse length of 12 ns. The results showed that optical properties, absorption and LIDT were influenced by the deposition parameters and annealing. However, scattering was little correlated with the deposition parameters. On the whole, the LIDT increased with increasing substrate temperature and oxygen pressure, whereas it increased firstly and then decreased upon increasing deposition rate. After annealing at 673 K for 12 h, the LIDT of films improved significantly. The dependence of possible damage mechanism on deposition parameters was discussed.     

Growth and structure of Bi0.5(Na0.7K0.2Li0.1)0.5TiO3 thin films prepared by pulsed laser deposition technique

Bi_0.5(Na_0.7K_0.2Li_0.1)_0.5TiO₃ (BNKLT) thin films were prepared on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition (PLD) technique. The films prepared were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The effects of the processing parameters, such as oxygen pressure, substrate temperature and laser power, on the crystal structure, surface morphology, roughness and deposition rates of the thin films were investigated. It was found that the substrate temperature of 600 °C and oxygen pressure of 30 Pa are the optimized technical parameters for the growth of textured film, and all the thin films prepared have granular structure, homogeneous grain size and smooth surfaces.     

Effect of deposition temperature on orientation and electrical properties of (K0.5Na0.5)NbO3 thin films by pulsed laser deposition

Lead-free ferroelectric K_0.5Na_0.5NbO₃ (KNN) thin films have been prepared on Pt/TiO₂/SiO₂/Si substrates by pulsed laser deposition process. The structures, crystal orientations and electrical properties of thin films have been investigated as a function of deposition temperature from 680 °C to 760 °C. It is found that the deposition temperature plays an important role in the structures, crystal orientations and electrical properties of thin films. The crystallization of thin films improves with increasing deposition temperature. The thin film deposited at 760 °C exhibits strong (0 0 1) preferential orientation, large dielectric constant of 930 and the remnant polarization of 8.54 μC/cm².     

(Al0.1Ga0.9)0.5In0.5P材料的MOCVD生长温度窗口研究

用来制作光电子器件的(Al0.1Ga0.9)0.5 In0.5P为直接带隙的四元合金材料,对应的发光波长为630 nm,在其LP-MOCVD (low press-metalorganic chemical vapor deposition)外延生长过程中温度的高低成为影响其质量的关键,找到合适的生长温度窗口很有必要.实验中分别在700℃,680℃,670℃和660℃的条件下生长出作为发光二极管有源区的(Al0.1Ga0.9)0.5 In0.5P多量子阱结构,通过PL谱的测试对比分析,找出最佳生长温度在670℃附近.之后对比各外延片的PL谱、表面形貌,并对反应室的气流场进行了模拟,对各温度下生长状况的原因作出了深入分析.分析得到,高温下In组分的再蒸发会引起晶格失配并导致位错;低温下O杂质的并入会形成大量非辐射复合中心影响晶体质量,因此导致了(Al0.1Ga0.9)0.5In0.5P生长温度窗口较窄,文章最后提出In源有效浓度的提高是解决高温生长的一条有效途径.     

Fabrication and vacuum annealing of transparent conductive Ga-doped Zn0.9Mg0.1O thin films prepared by pulsed laser deposition technique

In this study, highly transparent conductive Ga-doped Zn_0.9Mg_0.1O (ZMO:Ga) thin films have been deposited on glass substrates by pulsed laser deposition (PLD) technique. The effects of substrate temperature and post-deposition vacuum annealing on structural, electrical and optical properties of ZMO:Ga thin films were investigated. The properties of the films have been characterized through Hall effect, double beam spectrophotometer and X-ray diffraction. The experimental results show that the electrical resistivity of film deposited at 200 °C is 8.12 × 10⁻⁴ Ω cm, and can be further decreased to 4.74 × 10⁻⁴ Ω cm with post-deposition annealing at 400 °C for 2 h under 3 × 10⁻³ Pa. In the meantime, its band gap energy can be increased to 3.90 eV from 3.83 eV. The annealing process leads to improvement of (0 0 2) orientation, wider band gap, increased carrier concentration and blue-shift of absorption edge in the transmission spectra of ZMO:Ga thin films.     

Oxygen pressure dependent electroresistance in La0.9Sr0.1MnO3 thin films grown by laser molecular beam epitaxy

We report here studies on the influence of oxygen pressure on the electroresistance behavior of La_0.9Sr_0.1MnO₃ thin films fabricated by laser molecular beam epitaxy. It was found that the film deposited at lower oxygen pressure shows larger c-axis parameter, higher resistance, and more distinct electroresistance. These results reveal that the electroresistance of manganite thin films can be tuned by the conditions of film fabrication. Supported by the National Natural Science Foundation of China (Grant No. 10334070) and the National Key Basic Research Program of China (Grant No. 2004CB619004)     

Growth and characterization of Y2O3 thin films

Y₂O₃ thin films were grown on silicon (1 0 0) substrates by pulsed-laser deposition at different substrate temperatures and O₂ pressures. The structure and composition of films are studied by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The Y₂O₃ thin films deposited in vacuum strongly oriented their [1 1 1] axis of the cubic structure and the film quality depended on the substrate temperature. The magnitude of O₂ pressure obviously influences the film structure and quality. Due to the silicon diffusion and interface reaction during the deposition, yttrium silicate and SiO₂ were formed. The strong relationship between composition and growth condition was discussed.     

Chemical bath deposition of hausmannite Mn3O4 thin films

A low-temperature chemical bath deposition (CBD) technique has been used for the preparation of Mn₃O₄ thin films onto glass substrates. The kinetic behavior and the formation mechanism of the solid thin films from the aqueous solution have been investigated. Structure (X-ray diffraction and Raman), morphological (atom force microscope), and optical (UV-vis-NIR) characterizations of the deposited films are presented. The results indicated that the deposited Mn₃O₄ thin films of smooth surface with nanosized grains were well crystalline and the optical bandgap of the film was estimated to be 2.54 eV.     

Effect of oxygen pressure on structure and properties of Bi1.5Zn1.0Nb1.5O7 pyrochlore thin films prepared by pulsed laser deposition

The Bi₂O₃-ZnO-Nb₂O₅ (BZN) cubic pyrochlore thin films were prepared on Pt/TiO₂/SiO₂/Si(1 0 0) substrates by using pulsed laser deposition process. The oxygen pressure was varied in the range of 5-50 Pa to investigate its effect on the structure and dielectric properties of BZN thin films. It is found that oxygen pressure during deposition plays an important role on structure and other properties of BZN films. The BZN films deposited at temperature of 650 °C and at O₂ pressure of 5 Pa have an amorphous BZN and Nb₂O₅ phases but exhibits a cubic pyrochlore structure with a preferential (2 2 2) orientation when the oxygen pressure increases to 10 Pa. Dielectric constant and loss tangent of the films deposited at 10 Pa are 185 and 0.0008 at 10 kHz, respectively. The dielectric tunability is about 10% at a dc bias field of 0.9 MV/cm.     

Microstructure and dielectric properties of (Ba0.6Sr0.4)TiO3 thin films grown on super smooth glazed-Al2O3 ceramics substrate

Modified substrates with nanometer scale smooth surface were obtained via coating a layer of CaO-Al₂O₃-SiO₂ (CaAlSi) high temperature glaze with proper additives on the rough-95% Al₂O₃ ceramics substrates. (Ba_0.6Sr_0.4)TiO₃ (BST) thin films were deposited on modified Al₂O₃ substrates by radio-frequency magnetron sputtering. The microstructure, dielectric, and insulating properties of BST thin films grown on glazed-Al₂O₃ substrates were investigated by X-ray diffraction (XRD), atomic force microscope (AFM), and dielectric properties measurement. These results showed that microstructure and dielectric properties of BST thin films grown on glazed-Al₂O₃ substrates were almost consistent with that of BST thin films grown on LaAlO₃ (1 0 0) single-crystal substrates. Thus, the expensive single-crystal substrates may be substituted by extremely cheap glazed-Al₂O₃ substrates.