退火温度对(Bi0.8La0.2)2Ti2O7薄膜物理和电学性质的影响

采用化学溶液沉积法,在Si[100]衬底上制备了掺La的(Bi0.8La0.2)2Ti2O7薄膜,研究了退火温度对薄膜结晶性及电学性能的影响.研究发现,随着退火温度的升高,样品的结晶性越来越好;漏电流密度随之降低,表明绝缘性逐渐增强.实验证明该薄膜具有良好的绝缘性和较高的介电常数.     

铁磁(La0.7Ca0.3MnO3)/高温超导（YBa2Cu3O7）双层薄膜微结构的高分辨电镜研究

采用脉冲激光沉积法在LaAlO3(LAO)衬底上生长了YBa2Cu3O7/La0.7Ca0.3MnO3(YBCO/LC-MO)和La0.7Ca0.3MnO3/YBa2Cu3O7(LCMO/YBCO)两种外延薄膜,利用高分辨电子显微镜研究了其微观结构。在YBCO/LCMO/LAO薄膜中,LCMO以层-岛模式生长,并形成层状取向畴结构。YBCO层均由c轴取向晶粒组成,其中含有c/3平移畴界、额外CuO层及Y2O3第二相等缺陷结构。在LCMO/YBCO/LAO薄膜中,LAO衬底上初始生长的YBCO为c轴取向,至一定厚度(几个纳米)转为c与a轴混合生长。LCMO层在YBCO上外延生长并具有[100]m与[011]m混合取向畴结构。在LCMO/YBCO界面未观察到失配位错,因此二者界面属应变型界面。     

FeCoB-Al2O3软磁颗粒膜磁特性研究

采用射频磁控倾斜共溅射制备了一系列的(Fe40Co40B20)1-x(Al2O3)x软磁颗粒膜。分别研究了基片转速及溅射气压对FeCoB–Al2O3薄膜微波磁特性影响。并通过改变FeCoB靶以及Al2O3靶的溅射功率进一步调控了软磁颗粒膜的磁特性和电阻率。研究结果表明在基片转速为60 r/min,溅射气压为0.2 Pa,FeCoB靶的溅射功率为250 W,Al2O3靶的溅射功率为100 W时,获得的FeCoB-Al2O3软磁颗粒膜具备了优良的软磁特性、微波磁特性和较高的电阻率。薄膜的饱和磁化强度为1.73 T,易轴难轴矫顽力均小于80 A/m,电阻率为126.75μΩ·cm,共振频率高达2.22 GHz,磁导率实部在2 GHz仍大于400。     

氧控In2O3薄膜的光电性能

对比在控氧条件下制备态和退火态In₂O₃薄膜的微观结构和光电性能,分析两种状态中不同的氧作用机制。两种控氧行为都能够有效提高In₂O₃薄膜的晶格有序度和降低氧空位浓度,使其载流子浓度下降、迁移率提高和光学带隙变窄;等离子体制备过程中氧以高活性非平衡方式注入晶格,而退火时氧以低活性平衡态扩散的方式进入晶格;不同的氧作用机制使得退火态薄膜比制备态薄膜具有更少的结构缺陷、更高的氧空位浓度和更佳的透光导电性。     

阴极电沉积法同时制备TiO2薄膜和颗粒

采用阴极电沉积法电解钛酸四丁酯同时制备TiO2膜和颗粒,并讨论沉积条件对产物的影响。pH值是控制产物的主要参数。对比在紫外灯光照下不同产物不同时间下的光催化性能,比较其差异得出,酸性在pH值为1-2(加浓硫酸2-3mL)时的产物效果最好,光催化性能最好。并横向比较了加入硫酸体积相等的条件下,颗粒和薄膜的光催化效率。     

WC、ZrO2 、Cr2O3 和Al2O3 陶瓷颗粒/ 镍合金复合涂层微观组织结构的分形

采用等离子喷涂工艺, 制备了WC、ZrO₂ 、Cr₂O₃ 和Al₂O₃ 陶瓷颗粒/ 镍合金复合涂层。用X 射线衍射研究了陶瓷颗粒复合涂层相的分布; 用里氏硬度计测量陶瓷颗粒/ 镍合金复合涂层的硬度; 用CSS-1110 电子万能试验机研究陶瓷颗粒复合涂层的弯曲断裂性能。对涂层金相组织结构进行二值化处理, 利用Sandbox 法对陶瓷颗粒在金属基体中的分布进行研究, 得到了不同体积分数下陶瓷颗粒复合材料涂层的分维数。结果表明,陶瓷颗粒/ 镍合金复合涂层分维数随陶瓷颗粒含量的增加而增加, 与陶瓷颗粒种类无关; 陶瓷颗粒/ 镍合金复合涂层硬度和分维数随陶瓷颗粒直径减小而增加。随着分维数的增加, 复合涂层弯曲断裂角下降。      

铝合金/Al2O3-SiO2颗粒复合材料的试制和性能

本研究采用压力铸造法,把Al₂O₃-SiO₂颗粒与铝合金进行复合,并就所得到的复合材料与ZL108合金就磨损、拉伸等进行对比试验。试验结果表明:该复合材料不管在常温或高温(400℃)下其耐磨性(与zL108合金相比)提高十倍以上,而高温强度提高一倍以上。但在带有疲劳破坏的磨损中,其耐磨性提高不明显,而且对对磨材料还有加速磨损的缺点。     

氧化物La-Ca-Mn-O巨磁电阻薄膜的制备及其结构特性的研究

采用磁控溅射方法在ＺｒＯ２（００１）、Ｓｉ（００１）和玻璃衬底上成功地制备了ＬａＣａＭｎＯ（以下简称为ＬＣＭＯ）巨磁电阻薄膜。Ｘ－射线分析表明，ＺｒＯ２的晶格常数与ＬＣＭＯ的晶格常数失配虽然较大，仍可得到较好的ＬＣＭＯ薄膜。在Ｓｉ片上难以制备出致密完整的ＬＣＭＯ薄膜，其原因有待查明。玻璃衬底上可以获得纯相的ＬＣＭＯ巨磁电阻薄膜，在ＺｒＯ２衬底上制备的ＬＣＭＯ薄膜，其巨磁电阻效应在１５０Ｋ，３０００Ｇａｕｓ下达１３％左右。     

Al2O3颗粒对Al2O3p/Al复合材料时效析出的影响

本文通过采用硬度测量,差热分析及透射电镜综合研究了Al₂O₃p/6061复合材料在时效过程中的析出变化。结果表明,在Al₂O₃p/6061时效过程中,峰时效的主要强化相是β'相,并且以160℃,8小时时效的效果为最佳。     

射频反应溅射AL2O3薄膜组分研究

通过射频反应溅射的方法制备Al2O3薄膜,并研究其中AL和O的化学配比,并取得初步结果。实验以高纯Al作为靶材,高纯度O2为反应气体,在单晶(100)Si片上镀制Al2O3薄膜。用XPS能谱分析仪测试,不同氩氧比的情况下,氧化铝薄膜的化学配比,并与反应速率曲线进行对比确定氩氧比工艺。结果表明,应用此工艺制备的Al2O3薄膜具有良好的化学配比,得出了用试验方法确定反应溅射Al2O3薄膜氧氩比工艺的方法,此方法简单有效。     

PIXE & XRD analysis of nanocrystals of Fe, Ni and Fe2O3

Nanocrystalline materials have become a subject of both scientific and industrial importance in the past decade. The present work deals with the preparation of α-Fe and Ni powders by high-energy ball mill method and chemically prepared α-Fe₂O₃ powders of nano crystalline type respectively. There is a need to characterize the trace elements in order to check the purity of these samples. The results of trace element analysis of these nanocrystals by using PIXE, characterization and size determination by XRD using Debye-Scherrer formula with full-width at half-maximum(FWHM) have been discussed.Nanocrystallinity is examined already by (TEM,FTIR and MICRO-RAMAN) experiments done previously.     

Ozone sensing using In2O3-modified Ga2O3 thin films

It is shown that at elevated temperatures the conductance of an In ₂O₃-modified Ga₂O₃ thin film depends significantly and reversibly on the ozone concentration in the ambient air. This ozone sensitivity is much greater than with pure Ga ₂O₃ or In₂O₃ thin films, respectively. The ozone sensitivity of the In₂O₃-modified Ga₂O₃ thin film is characterized by an impressive selectivity, and is maximal at an operation temperature of about 600°C. The cross sensitivities to other gases present in ambient conditions are small compared to the ozone sensitivity, thus opening the way to use this system for ambient ozone monitoring. The results are discussed using an electron injection model     

Preparation and studies of Eu and Tb co-doped Gd2O3 and Y2O3 sol-gel scintillating films

Eu³⁺ (2.5 at.%) and Tb³⁺ (0.005-0.01 at.%) co-doped gadolinium and yttrium oxide (Gd₂O₃ and Y₂O₃) powders and films have been prepared using the sol-gel process. High density and optical quality thin films were prepared with the dip-coating technique. Gadolinium (III) 2,4-pentadionate and yttrium (III) 2,4-pentadionate were used as precursors, and europium and terbium in their nitrate forms were used as doping agents. Chemical and structural analyses (infrared spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy) were conducted on both sol-gel precursor powders and dip-coated films. The morphology of thin films heat-treated at 700 °C was studied by means of atomic force microscopy. It was shown that the highly dense and very smooth films had a root mean roughness (RMS) of 2 nm ± 0.2 (A = 0.0075 Tb³⁺) and 24 nm ± 3.0 (B = 0.01 Tb³⁺). After treatment at 700 °C, the crystallized films were in the cubic phase and presented a polycrystalline structure made up of randomly oriented crystallites with grain sizes varying from 20 to 60 nm. The X-ray induced emission spectra of Eu³⁺- and Tb³⁺-doped Gd₂O₃ and Y₂O₃ powders showed that Tb³⁺ contents of 0.005, 0.0075 and 0.01 at.% affected their optical properties. Lower Tb³⁺ concentrations (down to 0.005 at.%) in both systems enhanced the light yield.     

Dielectric properties of vacuum-deposited Yb2O3 films

The dielectric properties, i.e. the frequency (100 Hz–20 kHz) and temperature (0–125°C) dependence of the capacitance and loss factor tan δ, of vacuum-deposited Yb₂O₃ film capacitors with oxide thickness of 400–2000 Å were studied. The temperature coefficient of capacitance, the percentage variation ΔC/C(%) in capacitance at room temperature normalized at 1 kHz etc. were also investigated.     

Photoelectric currents in thin Al2O3 films

The photoconductivity in the 1–6 eV energy range was measured for Al₂O₃ prepared in three different ways with Mg, Al and Au counterelectrodes. C-V curves were taken on Al---Al₂O₃---p-Si and Au---Al₂O₃---p-Si devices. The leakage currents of Na---Al₂O₃---Al sandwiches were measured. From these measurements the barrier at the metal-oxide conduction band was found to be 3.5 ± 0.2 eV for Al. The photoconductivity with a threshold of about 2 eV is shown not to be due to the emitting metal electrodes for all three metals used. This threshold is independent of the work function of the counterelectrode.     

Preparation of In2O3 and tin-doped In2O3 films by a novel activated reactive evaporation technique

High quality films of In₂O₃ and tin-doped In₂O₃ were prepared by a novel activated reactive evaporation technique developed for use with resistively heated evaporation sources. Transparent conducting coatings of In₂O₃ have a sheet resistance of 80 Ω/□ with an optical transparency of more than 95% in the 0.4–1.6 μm wavelength range. Thin (0.4 μm) In₂O₃(Sn) films have a sheet resistance of 25 Ω/□ and an optical transparency as high as 99% at some wavelengths with an average transmission between 0.4 and 1.6 μm of 96%. Thicker films have a sheet resistance as low as 2.2 Ω/□. A comparison of the properties of In₂O₃(Sn) films with those of transparent conducting films produced by other techniques is made.     

Charge trapping characteristics of Al2O3/Al-rich Al2O3/SiO2 stacked films fabricated by radio-frequency magnetron co-sputtering

A thin-film structure comprising Al₂O₃/Al-rich Al₂O₃/SiO₂ was fabricated on Si substrate. We used radio-frequency magnetron co-sputtering with Al metal plates set on an Al₂O₃ target to fabricate the Al-rich Al₂O₃ thin film, which is used as a charge storage layer for nonvolatile Al₂O₃ memory. We investigated the charge trapping characteristics of the film. When the applied voltage between the gate and the substrate is increased, the hysteresis window of capacitance-voltage (C-V) characteristics becomes larger, which is caused by the charge trapping in the film. For a fabricated Al-O capacitor structure, we clarified experimentally that the maximum capacitance in the C-V hysteresis agrees well with the series capacitance of insulators and that the minimum capacitance agrees well with the series capacitance of the semiconductor depletion layer and stacked insulator. When the Al content in the Al-rich Al₂O₃ is increased, a large charge trap density is obtained. When the Al content in the Al-O is changed from 40 to 58%, the charge trap density increases from 0 to 18 × 10¹⁸ cm^− 3, which is 2.6 times larger than that of the trap memory using SiN as the charge storage layer. The device structure would be promising for low-cost nonvolatile memory.     

Glasses and glass-ceramics in the SrO–TiO2–Al2O3–SiO2–B2O3 system and the effect of P2O5 additions

The glass formation abilities of various compositions in SrO–TiO₂–Al₂O₃–SiO₂, SrO–TiO₂–B₂O₃–SiO₂, SrO–TiO₂–Al₂O₃–B₂O₃, and SrO–TiO₂–Al₂O₃–SiO₂–B₂O₃ systems were studied. Many new compositions were found to be suitable for the casting of crack-free, optically clear glasses of different color and with glass transition temperatures ranging from 595 to 775 °C. The crystallization behavior, structure, and thermal expansion behavior of selected glasses were analyzed by DTA, XRD, dilatometry, and heat treatment. The effect of P₂O₅ on the glass structure and crystallization behavior was also studied. P₂O₅ played a dual role depending on composition. In some glasses it acted as a nucleating agent while in others it suppressed crystallization. Heat treatment of borate and borosilicate glasses transformed them into glass-ceramics while comparable SrO–TiO₂–Al₂O₃–SiO₂ glasses showed a lower tendency to crystallize and form glass-ceramics under the same conditions.     

Effect of doping with Co2O3, TiO2, Fe2O3, and Mn2O3 on the properties of Ce0.8Gd0.2O2?δ

The effects of Co, Fe, Mn, and Ti oxide additions on the sinterability and crystal-chemical, thermal, and electrical properties of Ce_0.8Gd_0.2O_2−δ have been studied. The results indicate that these oxides enhance the sinterability of the mixed oxide, regardless of whether they were introduced before or after synthesis. The most effective sintering aid is Co₂O₃. The lattice parameters of Ce_0.8Gd_0.2O_2−δ samples containing different metal oxide additions (1 mol %) are refined in space group Fm3m. The temperature-dependent thermal expansion data are used to determine the linear thermal expansion coefficients of the samples. Manganese oxide additions reduce the electrical conductivity of Ce_0.8Gd_0.2O_2−δ, whereas the other dopants increase it in the order Ti < Fe < Co. The activation energy for conduction increases in the order Co < Ti < Fe < Mn. Original Russian Text ? E.Yu. Pikalova, A.N. Demina, A.K. Demin, A.A. Murashkina, V.E. Sopemikov, N.O. Esina, 2007, published in Neorganicheskie Material, 2007, Vol. 43, No. 7, pp. 830–837.