Giant magnetoresistance in Cu–Co films electrodeposited on n-Si

High quality Cu–Co alloy films with excellent metallic luster have been electrolytically deposited directly onto n-Si (1 0 0) substrate, thereby eliminating the need of a conducting seed layer, which is otherwise required when the films were grown on insulating substrates (Al₂O₃). The as-deposited Cu–Co films exhibit relatively higher magnetoresistance (MR) in comparison with the as-deposited films on Al₂O₃ under identical conditions. The observed increase in MR could be attributed to the reduced substrate current shunting. The MR further improves to 2.67% (at H=10 kOe) with vacuum annealing (at 425°C for 30 min) of the films on Si. This has been ascribed to the separation of Cu and Co phases resulting in a magnetic granular nanostructure. This value of MR of annealed films on Si is, however, lower in comparison with the value obtained for annealed films deposited on Al₂O₃. Glancing angle X-ray diffraction (GAXRD) has revealed the formation of copper silicide in these samples, which is responsible for the lower value of MR. Thus we have observed good MR with a copper silicide host matrix.     

Bias voltage dependence of tunneling magnetoresistance in granular C60–Co films with current-perpendicular-to-plane geometry

Voltage-dependence of the tunneling magnetoresistance effect in the granular C₆₀–Co films has been investigated for the samples with the current-perpendicular-to-plane geometry. The transport measurements under this geometry demonstrate that the granular C₆₀–Co films show an unusual exponential bias voltage dependence of the magnetoresistance ratio down to zero voltage. Small characteristic energies of less than 10's meV are derived from the temperature dependences of the characteristic voltage in the exponential relationship. Considering the magnitudes of the voltage drop between Co nanoparticles and also the effect of cotunneling on the energy values, the characteristic energies for the voltage-induced degradation of the spin polarization are found to show a satisfactory agreement with that for the thermally-induced one. It can be reasonably expected that the onset of magnetic disorder to the localized d-electron spins at the interface region of the C₆₀-based matrix (C₆₀–Co compound) with Co nanoparticles leading to the unusual voltage and temperature dependence of the magnetoresistance ratio and the spin polarization at low temperatures.     

Giant Faraday rotation in Fe–ZnSe granular films

The giant magneto-optical Faraday effect (giant Faraday rotation) of ferromagnetic metal–semiconductor matrix Fe–ZnSe granular films prepared by radio frequency sputtering is studied. The result shows that the Faraday rotation angle θ_F value of the granular films sample with Fe volume fraction x=35% is of the order of 10⁵ °/cm at room temperature. Temperature dependence of the θ_F of Fe_0.35(ZnSe)_0.65 granular films shows that θ_F value, below 150 K, increases rapidly with the decrease of the temperature, and when T=10 K θ_F value is 6×10⁵ °/cm. Through the study of the structure and dependence of magnetic properties on temperature, it has been found that the remarkable increase of the θ_F value of Fe_0.35(ZnSe)_0.65 granular films below 150 K seems to arise from the sp–d exchange interaction inside the granular films.     

Preparation and characteristics of?a?BaO–Al2O3–B2O3–SiO2–La2O3 glass ceramic via spray pyrolysis

The characteristics of a BaO–Al₂O₃–B₂O₃–SiO₂–La₂O₃ glass ceramic prepared by spray pyrolysis were studied. Glass powders with spherical shape and amorphous phase were prepared by complete melting at a preparation temperature of 1 500°C. The mean size and geometric standard deviation of the powders prepared at the temperature of 1 500°C were 0.6 μm and 1.3. The glass powders had similar composition to that of the spray solution. The glass transition temperature (T _g) of the glass powders was 600.3°C. Two crystallization exothermic peaks were observed at 769.3 and 837.8°C. Densification of the specimen started at a sintering temperature of 600°C, in which Ba₄La₆O(SiO₄)₆ as main crystal structure was observed. Complete densification of the specimen occurred at a sintering temperature of 800°C. The specimens sintered at temperatures above 800°C had main crystal structure of BaAl₂Si₂O₈.     

Al2O3增强的Co2-C98/Al2O3/Si异质结的光伏效应

随着能源危机的加剧,太阳能电池作为开发和利用太阳能的一种普遍形式, 日益受到世界各国的重视.随着太阳能电池向着高效率、薄膜化、无毒性和原材料丰富的方向发展, 单纯的硅系太阳能电池已经无法达到这样的要求,因此新的材料和工艺的开发利用迫在眉睫. 本文研究了碳材料在硅异质节上实现光伏效应的改善及其可能在太阳能电池上的应用. 采用脉冲激光沉积方法制备的Co₂-C₉₈/Al₂O₃/Si异质结构在标准日光照射 (AM1.5, 100 mW/cm²)条件下,可获得0.447 V的开路电压和18.75 mA/cm²的电流密度, 转换效率可达3.27%.通过电容电压特性和暗条件下的电输运性能测量, 证明了氧化铝层的引入不但对单晶硅的表面起到了物理钝化作用,减小了反向漏电流, 使异质结界面缺陷、界面能级和复合中心减少,还起到了场效应钝化作用, 增加了异质结界面的势垒高度,增加了开路电压,使异质结的光伏效应显著增强.     

Structural characterization of β-V2O5 films prepared by DC reactive magnetron sputtering

β-V₂O₅ films were successfully prepared on silicon substrates by direct current (DC) reactive magnetron sputtering. X-ray diffraction (XRD), Raman spectra and field emission scan electron spectroscopy (SEM) were used to characterize the samples. Results revealed that the deposition temperature significantly influenced on the crystal structure of V₂O₅ films in the growth process. When the deposition temperature was below 500 °C, the sputtered film exhibited the α-V₂O₅ structure. However, β-V₂O₅ film was successfully obtained at 550 °C. High deposition temperature might provide V and O ions high mobility and energy in the reactive sputtering process, which induced the metastable β-V₂O₅ phase formed. The thermal stability of β-V₂O₅ film was studied by micro-Raman spectroscopy. The structure of sputtered β-V₂O₅ film was unstable under high temperature conditions (beyond 500 °C).     

Al2O3衬底MgB2超薄膜的研究

我们利用混合物理化学气相沉积法(Hybrid physical-chemical vapor deposition简称为HPCVD)在(000l)Al2O3衬底上制备了系列干净的MgB2超薄膜,并通过R-T测量、SEM测量、M-T测量、XRD测量对它们进行了表征,探究了其超导电磁性能和薄膜的生长机制.其中的7.5nm厚的MgB2超薄膜为已报导的蓝宝石衬底上生长的性能最高的超薄膜.     

Thermal stability of alumina thin films containing γ-Al2O3 phase prepared by reactive magnetron sputtering

The paper reports on thermal stability of alumina thin films containing γ-Al₂O₃ phase and its conversion to a thermodynamically stable α-Al₂O₃ phase during a post-deposition equilibrium thermal annealing. The films were prepared by reactive magnetron sputtering and subsequently post-deposition annealing was carried out in air at temperatures ranging from 700 °C to 1150 °C and annealing times up to 5 h using a thermogravimetric system. The evolution of the structure was investigated by means of X-ray diffraction after cooling down of the films. It was found that (1) the nanocrystalline γ-Al₂O₃ phase in the films is thermally stable up to 1000 °C even after 5 h of annealing, (2) the nanocrystalline θ-Al₂O₃ phase was observed in a narrow time and temperature region at ≥1050 °C, and (3) annealing at 1100 °C for 2 h resulted in a dominance of the α-Al₂O₃ phase only in the films with a sufficient thickness.     

Growth of β-Ga2O3 nanorods by ammoniating Ga2O3/V thin films on Si substrate

This paper reports that/3-Ga2O3 nanorods have been synthesized by ammoniating Ga2O3 films on a V middle layer deposited on Si（111） substrates. The synthesized nanorods were confirmed as monoclinic Ga2O3 by x-ray diffraction,Fourier transform infrared spectra. Scanning electron microscopy and transmission electron microscopy reveal that the grown β-Ga2O3 nanorods have a smooth and clean surface with diameters ranging from 100 nm to 200 nm and lengths typically up to 2μm. High resolution TEM and selected-area electron diffraction shows that the nanorods are pure monoclinic Ga2O3 single crystal. The photoluminescence spectrum indicates that the Ga2O3 nanorods have a good emission property. The growth mechanism is discussed briefly.     

磁性隧道结Ni80Fe20/Al2O3/Co的研究

用等离子体氧化形成中间绝缘层的方法可重复制备出具有隧道磁电阻（TMR)效应的Ni₈₀Fe₂₀/Al₂O₃/Co磁性隧道结.光透射谱等实验结果表明等离子体氧化能可控制地制备较致密的Al₂O₃绝缘层.样品的TMR比值在室温下最高可达6.0％,反转场可低于800A/m,相应的平台宽度约为2400A/m.结电阻R_j的变化范围从百欧到几百千欧,并且TMR比值随零磁场结偏压增大单调减小. 关键词：     

Broadband near-IR emission and temperature dependence in Er/Tm co-doped Bi2O3–SiO2–Ga2O3 glasses

The broadband near-IR emission has been investigated in a series of Er/Tm co-doped Bi₂O₃–SiO₂–Ga₂O₃ (BSG) glasses with 800 nm laser diode as an excitation source. A broadband emission extending from 1350 to 1650 nm with a full width at half maximum (FWHM) around 165 nm is obtained in 0.2 wt% Er₂O₃ and 1.0 wt% Tm₂O₃ co-doped BSG glass. The fluorescence decay curves of glasses are measured and maximum energy transfer efficiency from Er³⁺ to Tm³⁺ reaches 71% when Tm³⁺ concentration is 1.0 wt%. The temperature dependence of the broadband emission spectra in Er³⁺–Tm³⁺ co-doped BSG glass is also recorded to further understand the energy-transfer processes between Er³⁺ and Tm³⁺. The present work suggests that Er/Tm co-doped BSG glasses can be a potential candidate for broadband integrated amplifier.     

The effect of intragranular microstress in Al2O3—SiC nanocomposites

A theoretical model is established to investigate the intragranular particle residual stress in Al2O3-SiC nanocomposites.Using this model,we calculate the average compressive stress on the Al2O3 grain boundary(GB) and the average tensile stress within Al2O3 grains caused by SiC nanoparticles.The normal compressive stress strengthens the GB,and the average tensile stress weakens the grains.The model gives a reasonable interpretation of the strength changes of Al2O3-SiC nanocomposites with the number of SiC particles.     

MoO3/Al2O3催化剂中Mo分散的正电子研究

用浸渍法制备了一系列不同Mo含量的MoO₃/Al₂O₃催化剂.测量了这些样品的正电子湮没寿命谱(PALS)与符合多普勒展宽(CDB)谱,以研究其孔洞结构以及Mo分散.正电子寿命测量结果表明,Al₂O₃载体中存在两种不同尺寸的孔洞.掺入MoO₃之后,Mo原子主要进入Al₂O₃的大孔中,使孔洞体积减小.符合多普勒展宽谱结果表明,当MoO 关键词： 3/Al₂O₃催化剂')" href="#">MoO₃/Al₂O₃催化剂 正电子湮没寿命谱 符合多普勒展宽 Mo 分散     

磁性隧道结Ni80Fe20/Al2O3/Co的制备和物性

用等离子体氧化形成绝缘层的方法，重复性地制备出了Ni     

Fe/Al2O3/Fe隧道结特性分析

用离子束溅射方法制备磁性隧道结(MTJ). 研究MTJ样品的隧道结磁电阻(TMR)效应.用X射线 光电子能谱分析了MTJ的软、硬磁层和非磁层及其界面的化学组成与微结构.研究了MTJ的微 结构对氧化铝势垒高度与有效宽度和TMR效应的影响. 关键词： 磁性隧道结 X射线光电子能谱 隧道结磁电阻     

Electroluminescence properties of In-doped Zn2SiO4 thin films prepared by sol–gel process

The effect of In doping on the electroluminescence (EL) properties of Zn₂SiO₄:In thin films was investigated. In-doped Zn₂SiO₄ thin films were deposited on BaTiO₃ substrates and their EL properties were characterized in this study. X-ray powder diffraction patterns of In-doped Zn₂SiO₄ powders revealed a single phase of Zn₂SiO₄ for In concentrations up to approximately 1.5 mol%, whereas a secondary phase of In₂O₃ was observed for In concentrations in the range of 2–10 mol%. The maximum luminance of thin film electroluminescent (TFEL) devices varied significantly with the amount of In doping. The highest luminance with blue emission was obtained when 2 mol% In was doped. The blue emission of In-doped Zn₂SiO₄ thin film may be related to the In substitution for Zn. The 2 mol% In-doped Zn₂SiO₄ thin film exhibited blue emission with CIE color coordinates of x=0.208 and y=0.086.     

Investigation of structural,physical and optical properties of CeO2–Bi2O3–B2O3 glasses

xCeO₂–30Bi₂O₃–(70−x) B₂O₃ glasses are synthesized by using the melt quench technique. A number of studies such as XRD, density, molar volume, optical band gap, refractive index and FTIR spectroscopy are employed to characterize the glasses. The band gap decreases from 2.15 to 1.61 eV, refractive index increases from 2.67 to 2.93 and density increases from 4.151 to 4.633 g/cm³. The decrease in band gap with CeO₂ doping approaches the semiconductor behavior. FTIR spectroscopy reveals that incorporation of CeO₂ into glass network helps to convert the structural units of [BO₃] into [BO₄] and results in Bi–O bond vibration of [BiO₆].     

Intense up-conversion emissions of Yb3+/Dy3+ co-doped Al2O3 nanopowders prepared by non-aqueous sol—gel method

Yb³⁺/Dy³⁺ co-doped Al₂O₃ nanopowders have been prepared by the non-aqueous sol-gel method and their up- conversion photoluminescence spectra are measured under excitation by 980-nm semiconductor laser. The results show that there are comparatively abundant spectra of up-conversion emissions centered at 378, 408, 527 and 543, and 663 nm, corresponding to ⁴G_9/2 → ⁶H_13/2, ⁴G_9/2 → ⁶H_11/2, ⁴I_15/2 → ⁶H_13/2, and ⁴F_9/2 → ⁶H_11/2 transitions of Dy³⁺, respectively. Two-photon and three-photon processes are involved in ultraviolet, violet, green, and red up-conversion emissions. The energy transition between Yb³⁺ and Dy³⁺ is discussed.     

电爆炸丝法制备纳米Al2O3粉末

 设计了电爆炸金属丝产生纳米金属氧化物粉末的实验装置，金属丝电爆炸腔采用圆筒结构，纳米粉末经过微孔滤膜过滤收集。成功制备了纳米Al₂O₃粉末，其平均粒度达到64.9 nm。对电爆炸金属丝产生纳米Al₂O₃粉末的物理条件进行了研究。结果表明实验条件对粉末粒度有重要影响：随气压的增加粉末平均粒度变大；随金属丝直径增大粉末平均粒度变大；粉末的平均粒度与电容器的初始储能也有一定的关系。