厚度依赖的La_(0.33)Pr_(0.34)Ca_(0.33)MnO_3的磁学性质北大核心CSCD

采用激光脉冲沉积(PLD)方法,在LaAlO3(001)衬底上外延生长了不同厚度的La0.33Pr0.34Ca0.33MnO3薄膜,并研究了薄膜晶格常数及居里温度随薄膜厚度的变化行为.XRD表征结果表明,随着薄膜厚度的增加,LPCMO的c轴长度逐渐减小,反映了衬底对薄膜的应力作用.薄膜磁矩随温度变化的测量结果说明,随着薄膜厚度的减小,TC及TB向低温移动,反映了薄膜厚度或者衬底应力作用对LPCMO磁性的直接影响.     

Al2O3陶瓷衬底碳离子预注入对金刚石薄膜应力的影响研究

通过对Al2O3陶瓷衬底进行碳离子预注入，大大降低了Al2O3陶瓷衬底上金刚石薄膜的应力，且金刚石薄膜中的压应力随碳离子注入剂量的增加而线性下降.通过对Al2O3陶瓷衬底注入前后的对比分析表明，高能量的碳离子注入Al2O3陶瓷衬底以后，并没有产生过渡层性质的新相，而是大量累积在Al2O3晶格的间隙位，使Al2O3晶格发生畸变.而且，随着碳离子注入剂量的增加，Al2O3基体内晶格畸变加剧，注入层残余压应力也随之上升.当金刚石薄膜沉积以后，在降温的过程中衬底这部分残余应力得到释放，从而部分弛豫了金刚石薄膜中的 关键词： 金刚石薄膜 应力 离子注入 Al2O3陶瓷     

射频磁控溅射法生长MgxZn1-xO薄膜的结构和光学特性

用射频磁控溅射法在80℃的衬底温度下制备出Mg_xZn_1-xO(0≤x ≤030)薄膜.x射线 衍射(XRD)结果表明，Mg_xZn_1-xO薄膜为单相六角纤锌矿结构， 没有形成任何显著 的MgO分离相，Mg_xZn_1-xO薄膜的择优取向平行于与衬底垂直的 c轴；c轴晶格常数随着Mg含量的增加逐渐减小.在Mg_xZn_1-xO薄膜的光透射谱中出现 锐利的吸收边，由透 射谱估算出Mg_xZn_1-xO薄膜的带隙宽度由332eV(x=0)线性地 增加到396eV(x=030). 关键词： xZn_1-xO薄膜')" href="#">Mg_xZn_1-xO薄膜 射频磁控溅射 Mg含量     

高温超导YBa2Cu3O7-δ-Y2O3多层薄膜的制备及性能表征

采用脉冲激光沉积技术(PLD)在LaAlO3(100)单晶衬底上外延生长YBa2Cu3O7-δ-Y2O3多层薄膜,用X射线衍射技术(XRD)分析薄膜的物相结构和外延特性,通过原子力显微镜(AFM)观察薄膜的表面形貌.本文主要研究了最佳工艺参数下交替生长多层YBCO-Y2O3膜的超导性能.结果表明,YBa2Cu3O7-δ-Y2O3薄膜为纯c轴取向外延生长,临界电流密度Jc(H=0或H//C)均高于纯YBCO薄膜,纳米Y2O3起到磁通钉扎中心作用.     

Mg掺杂对AlGaN薄膜特性的影响

利用高精度x射线衍射和拉曼散射光谱，对MOCVD生长的不同Mg掺杂量的AlGaN薄膜的c轴 晶格常数、摇摆曲线和拉曼频移进行测量发现：当Mg掺杂剂量较小时，E2模式向 低频方向漂移表明张力应力有所增加，但是摇摆曲线和A1(LO)模式半高宽减小表 明薄膜质量有所提高；随着Mg掺杂剂量的增加，E2模式反向漂移表明此时薄膜中 存在压力应力，同时薄膜质量有所下降.最后根据拉曼频移和应力改变进行拟合得出相应的 线性表达式为Δσ＝-0298+0562·ΔE. 关键词： AlGaN:Mg 异质外延 x射线衍射 拉曼散射     

La,Nb共掺杂BiFeO_3薄膜中的光致应变效应及应力调控

本文利用反射式飞秒抽运-探测技术,系统研究了飞秒激光诱导La和Nb共掺杂的铁酸铋(Bi0.8La0.2Fe0.99Nb0.01O3)薄膜中纵向声学声子的动力学过程,声学声子的产生源于光致应变效应.实验发现不同的衬底(ZrO2和PbMg1/3Nb2/3-PbTiO3)可以调制外延生长的Bi0.8La0.2Fe0.99Nb0.01O3薄膜的面外弹性系数C⊥.此外,通过对压电晶体衬底PbMg1/3Nb2/3-PbTiO3外加电压,实现了对薄膜应力的调制.     

双掺杂La0.67+1.33xSr0.33-1.33xMn1-xMgxO3体系的磁性和输运行为

用标准的固相反应法制备了双掺杂La0.67 1．33xSr0．33-1．33xMn1-xMgxO3(x=0．00,0．05,0．10,0．15,0．20,0．25)多晶样品,研究了它们的磁性和输运行为。对x=0．10和0．15,在温度高于Tc^cnset时出现相分离;对x=0．20和0．25,在低温区出现反铁磁行为。低掺杂样品ρ-T关系存在金属．绝缘体相变,高掺杂样品在测量温区内仅显示绝缘体行为。这些奇异现象用M-H关系、ESR曲线和拉曼光谱给予了很好的解释。     

薄膜光学 制膜技术与装置

O484．1 2005042881 PLD法制备纳米类金刚石薄膜及衬底温度的影响=Syn- thesis of nanoscale diamond-like carbon films by PLD and the dependence of substrate temperature[刊,中]／欧阳钢 (湘潭大学材料与光电物理学院,湖南,湘潭(411105)),郭建…／／光电子·激光,-2004,15(12),-1456-1459,1463 利用脉冲激光沉积(PLD)技术在O2氛围下于α- Al2O3(0001)基片上制备出纳米类金刚石薄膜。借助扫描电子显微镜(SEM)、原子力显微镜(AFM)和Raman光谱分析了薄膜的形貌和结构随沉积时衬底温度的变化情况。     

[(SrTiO3)n/(SrTi0.8Nb0.2O3)m]20/LaAlO3超晶格的制备及其激光感生热电电压效应

采用脉冲激光沉积(PLD)镀膜技术在倾斜10°的LaAlO3(100)单晶衬底上制备了(SrTiO3)n/(SrTi0.8Nb0.2O3)m系列超晶格.在超晶格薄膜的XRD图谱中清楚地观察到周期调制的卫星峰结构.从卫星峰的分布计算了超周期,进而得到了在生长SrTiO3和SrTi0.8Nb0.2O3时的沉积速率,分别为0.78 /pulse和0.57 /pulse.在超晶格薄膜中发现了激光感生热电电压(LITV)效应,说明这种人造原子层热电堆结构具有Seebeck系数各向异性.研究发现,在SrTiO3介电层厚度n=46.8 nm,SrTi0.8Nb0.2O3导电层厚度m=19.0 nm时LITV信号的平均峰值电压最大U -P=0.7 V/mJ·mm,n=46.8 nm,m=11.4 nm时LITV信号的平均响应时间最小τ -=124 ns.     

厚度与应变效应对La0.67 Ca0.33 MnO3薄膜电输运与居里温度的影响

在厚度为25-400nm范围内,系统地研究了(001)SrTiO3(STO),(001)LaAlO3(LAO)衬底上La0.67Ca0.33MnO3(LCMO)薄膜的电输运与居里温度TC随薄膜厚度及衬底的变化.结果表明,随薄膜变薄,电阻率ρ增加,TC降低.对于同一薄膜厚度,LCMO/STO薄膜的ρ大于LCMO/LAO基上的薄膜的ρ.TC与衬底的依赖关系则与ρ相反.分析表明,LCMO薄膜的低温区电阻温度(ρ-T)符合关系式ρ=ρ0+Bωs/sinh2(hωs/2/kBT)+CTn,其中ρ0为剩余电阻;等号右端第二项反映软光学模声子对电子散射的贡献;第三项包括其余可能散射机理在电输运过程中所起的作用;B,ωs(软光学模声子的平均频率)与C都为拟合系数.高温区的电输运则由小极化子跃迁模型ρ=DT×exp(Ea/kBT)描述(Ea为极化子激发能).根据ρ0,ωs,Ea以及TC变化,初步讨论了薄膜中的厚度与应变效应.进一步研究发现ωs,Ea的变化与TC相关,从而说明极化子效应为影响TC变化的主要因素.     

Absence of traditional magnetoresistivity mechanisms in Sr(2)FeMoO(6) thin films grown on SrTiO(3), MgO and NdGaO(3) substrates

Magnetoresistive double perovskite Sr(2)FeMoO(6) thin films were grown with two different deposition pressures on SrTiO(3), MgO and NdGaO(3) substrates by pulsed laser deposition and thorough structural, magnetic and magneto-transport characterization was made. According to x-ray diffraction, all the films were phase pure and fully textured. Indication of substrate dependent strain and low angle grain boundaries was found, especially in films on MgO. Both the deposition pressure and the choice of the substrate have a strong influence on the saturation magnetization, M(s), and Curie temperature, T(C). The structural and magnetic data indicate the presence of anti-site disorder (ASD) in the films. The temperature dependence of resistivity showed semiconductive behaviour at temperatures below 100 K and metallic behaviour at higher temperatures. The semiconductive behaviour was found to increase with increasing ASD. In good quality films, up to 12% negative magnetoresistance (MR) was observed and films grown on MgO and NGO substrates also showed low field MR. However, the most significant observation of this study was that the magnetoresistivity of these Sr(2)FeMoO(6) thin films could not be explained with any traditional MR mechanism, but carried the clear signature of superposition of different mechanisms, in particular low angle grain boundary tunnelling and suppression of antiferromagnetically ordered domains under a magnetic field.     

The structure of strained perovskite KTaO(3) thin films prepared by pulsed laser deposition

Epitaxial perovskite potassium tantalate (KTaO(3)) films with thicknesses of 7.4-36?nm are grown on SrTiO(3)(001) substrates by pulsed laser deposition. X-ray diffraction (XRD) analysis reveals evolution of lattice strain with increasing film thickness. A biaxial compressive in-plane strain as large as -?2.1% is obtained in the 7.4?nm-thick film. A bi-layer microstructure is detected in the 18?nm-thick film, suggesting the possibility for an abrupt strain relaxation.     

La0.67Ca0.33MnO3薄膜中的各向异性应变与电荷有序

本文采用脉冲激光沉积法在NdGaO3(001)单晶衬底上制备了一系列的La0.67Ca0.33MnO3薄膜,实验主要研究了薄膜的输运性质.La0.67Ca0.33sMnO3块材是铁磁金属基态,而La0.67Ca0.33MnO3/NdGaO3(001)薄膜由于各向异性应变的存在,可以观测到电荷有序绝缘相的出现.薄膜样品表...     

Growth and photoluminescence properties of inclined ZnO and ZnCoO thin films on SrTiO₃（110） substrates

ZnO thin film growth prefers different orientations on the etched and unetched SrTiO 3(STO)(110) substrates.Inclined ZnO and cobalt-doped ZnO(ZnCoO) thin films are grown on unetched STO(110) substrates using oxygen plasma assisted molecular beam epitaxy,with the c-axis 42 inclined from the normal STO(110) surface.The growth geometries are ZnCoO[100]//STO[110] and ZnCoO[111]//STO[001].The low temperature photoluminescence spectra of the inclined ZnO and ZnCoO films are dominated by D 0 X emissions associated with A 0 X emissions,and the characteristic emissions for the 2 E(2G)→ 4A2(4F) transition of Co 2+ dopants and the relevant phonon-participated emissions are observed in the ZnCoO film,indicating the incorporation of Co 2+ ions at the lattice positions of the Zn 2+ ions.The c-axis inclined ZnCoO film shows ferromagnetic properties at room temperature     

Strain-induced properties of epitaxial VOx thin films

We have grown VOx thin films on different substrates in order to investigate the influence of epitaxial strain on the transport properties. We found that the electric conductivity is much larger for films grown under compressive strain on SrTiO3 substrates, as compared to bulk material and VOx films grown under tensile strain on MgO substrates. A clear crossover from metallic to semiconducting behavior is observed when increasing the oxygen content x. Apparently, the application of strain induces a Mott-Hubbard insulator-to-metal transition in VOx<1. The VOx/SrTiO3 films show an unexpected large positive magnetoresistance effect at low temperatures, which is not found in the VOx films grown under tensile strain on MgO or on a substrate with a similar lattice parameter.     

La0.67Ca0.33MnO3/NdGaO3(001)薄膜中外延应变诱导的各向异性磁阻效应

本文使用脉冲激光沉积方法在正交的NdGaO3(001)衬底上外延生长了La0.67Cao.33MnO3薄膜.退火后,由于外延应变引起薄膜正交畸变增强,薄膜在低于250K的整个温度区间都出现了铁磁金属态和反铁磁绝缘态的相分离和相竞争.这两相的竞争强烈依赖于磁场相对晶轴的方向,由此导致存在于很宽温度范围内的低场各向异性磁阻...     

Polar dependent in-plane electric transport of epitaxial ZnO thin films on SrTiO(3) substrates

Polar (001) and nonpolar (110) ZnO epitaxial thin films were grown on SrTiO(3) substrates by the pulsed laser deposition method and the in-plane electric transport was investigated. Both films display semiconducting behavior. The polar thin films have linear I-V relations with mobility increasing almost linearly with temperature. In contrast, for nonpolar ZnO thin films, the I-V curves are symmetric and nonlinear with room temperature resistivity 30 times larger than that of polar thin films. We conclude that in nonpolar ZnO thin films the bound polarization charge induced barrier limits the carrier transport. Instead, for polar thin films, the polar effect on the in-plane transport is negligible, and the charged dislocation scattering is dominant. Our observations suggest the polar effect should be considered in the design of ZnO related devices.     

Atomic imaging and direct phase retrieval using anomalous surface x-ray diffraction

The application of multi-wavelength anomalous diffraction to thin films, interfaces and surface structures is presented. The method directly determines the amplitudes and phases of the complex surface structure factors from surface x-ray diffraction data, measured at three different energies around the absorption edge of one of the elements present in the film. Thereby, one is able to directly Fourier transform the data, which immediately provides meaningful and unambiguous electron-density distributions. These serve as a starting point for subsequent structural refinement. The robustness of the algorithm was evaluated on simulated data as a proof of principle. The experimental limitations and their effect on the method will be discussed as well as stability tests for the algorithm, such as the positions of the anomalous scatterers and the interfacial roughness. It will be shown that the method can be applied to real structures. The algorithm was tested on real data from a thin film of SrTiO(3) grown on NdGaO(3)(110).     

Effect of substrate strain on lattice structure,electrical resistivity,and optical conductivity of Nd0.5Sr0.5MnO3 thin films grown on SrTiO3

In this study, we investigated the lattice structure, electrical resistivity, and optical conductivity of Nd_0.5Sr_0.5MnO₃ thin films grown on SrTiO₃ (001) and SrTiO₃ (011) substrates. The thin film on SrTiO₃ (001) experiences isotropic tensile strain and shows characteristics of the semiconducting ground state. On the other hand, the thin film on SrTiO₃ (011) experiences anisotropic tensile strain, which means that one of the two in-plane lattice axes is fixed by the substrate lattice and the other axis is relaxed. The thin film shows the insulator–metal phase transition at 220 K and characteristics of the charge-ordered insulating ground state below 150 K. By comparing the single crystal data of the lattice along with the resistivity and optical conductivity, we suggest that the substrate strain affects the electronic structure as well as the carrier dynamics of the Nd_0.5Sr_0.5MnO₃ thin films. We propose the possible ground states formed in the thin films.     

Effects of growing conditions on the electric and magnetic properties of strained La2/3Sr1/3MnO3 thin films

We investigate the growing condition dependences of magnetic and electric properties of the La_2/3Sr_1/3MnO₃ thin films grown on SrTiO₃（001） substrates.With reducing the film thickness and growth pressure,the Curie temperature（T_c）drops off,and the magnetism and metallicity are suppressed.At an appropriate deposition temperature,we can obtain the best texture and remarkably enhance the magnetic and electrical properties.However,the resistivity of film cannot be modulated by changing the dc current and green light intensity.This result may be induced by the coherent strains in the epitaxially grown film due to its lattice mismatching that of the SrTiO₃ substrate.Furthermore,we show that the relations between the magnetism and the resistivity for the typical films with different thickness values.For the 13.4-nm-thick film,the R-T curve presents two transition behaviors:insulator-to-metal and metal-to-insulator in the cooling process:the former corresponds to magnetic transition,and the later correlates with thermal excitation conduction.