SrMnO3阻挡层对La0．8Sr0．2Mn03／Si异质结整流特性的改善

对用磁控溅射方法在硅基上直接沉积La0.8Sr0.2MnO，和引入SrMnO，（SMO）阻挡层后沉积La0.8Sr0.2MnO，进行了比较。对薄膜结构用X射线衍射试验表征，并分析了薄膜取向生长的原因。卢瑟福背散射实验结果表明，SMO阻挡层的引入显著地削弱了LSMO和si界面层处的元素互扩散。电学测试表明LSMO／SMO／Si结构比LSMO／Si结构具有更好的P—n结整流特性，而且随SMO缓冲层的增厚，整流特性反而削弱。     

Si衬底上La0.8Sr0.2MnO3/SrMnO3双层结构研究

利用磁控溅射方法在Si(100)衬底上首先生长SrMnO3(SMO)作为缓冲层,再沉积La0.8Sr0.2MnO3(LSMO)薄膜,得到(110)面择优生长的LSMO/SMO双层结构.利用X射线衍射仪分析了SMO缓冲层的结构特征对LSMO薄膜择优取向生长的影响;利用Rutherford背散射(RBS)分析了LSMO/SMO间的界面情况.结果表明以SMO作为单一缓冲层时,不仅可以实现LSMO薄膜在Si(100)衬底上的(110)面的择优生长,而且LSMO/SMO的界面扩散现象也不明显.     

(Bi_(0.8)La_(0.2)FeO_3)_(0.8)-(NiFe_2O_4)_(0.2)材料的合成及薄膜多铁性能

研究了Bi0.8La0.2FeO3单相陶瓷的合成,并采用脉冲激光沉积法,在SrTiO3(100)(STO)基底上,以La0.7Sr0.3MnO3(LSMO)为缓冲层,制备了(Bi0.8La0.2FeO3)0.8-(NiFe2O4)0.2(BLFO-NFO)多铁薄膜。通过X射线衍射仪和场发射扫描电子显微镜确定了BLFO-NFO多铁薄膜的显微结构,通过标准铁电测试系统(RT-66A)和振动样品磁强计(VSM)分别测试了BLFO-NFO多铁薄膜的铁电性能和铁磁性能。研究发现:BLFO-NFO多铁薄膜沿(100)方向外延生长,晶粒为70nm,它具有明显的电滞回线和磁滞回线。     

光谱拟合法确定一种钙钛矿结构薄膜材料的复数光学常数

为了获得一种钙钛矿结构镧锶锰氧La0.8Sr0.2MnO3薄膜材料的复数光学常数,利用光学薄膜原理和数学优化方法,并基于钙钛矿结构材料的色散模型,对磁控溅射技术制备的不同厚度的镧锶锰氧薄膜在波数400～1250cm-1范围内的反射光谱进行了全谱拟合,并由拟合参数确定了薄膜的复数光学常数.拟合结果显示,测试光谱和拟合光谱较为一致,说明钙钛矿结构材料的色散模型适用于描述La0.8Sr0.2MnO3薄膜的光学特性,利用该色散模型并通过光谱拟合法获得La0.8Sr0.2MnO3薄膜的复数光学常数是获得此材料光学特性的一种有效的方法.     

La2/3Sr1/3MnO3薄膜的输运及激光反射率特性

用磁控溅射方法制备了钙钛矿锰氧化合物La2/3Sr1/3MnO3(LSMO)单晶外延薄膜,该薄膜发生顺磁绝缘-铁磁金属相变的转变温度Tc≈330K.在室温(T=293K),偏置电流对LSMO薄膜输运性质的影响表明,随着电流的增大,材料的晶格畸变加强,电阻值增大,同时薄膜的激光反射率减小.用固体光学理论对其进行定性解释.     

La_(1-x)Sr_xMnO_3薄膜的制备、微观结构及电性能

以无机盐为原料,采用溶胶-凝胶法在Si衬底上制备了La1-xSrxMnO3(LSMO)薄膜。XRD和TEM测试表明LSMO薄膜呈现纳米多晶菱形钙钛矿结构,薄膜的(012)、(110)晶面间距分别为0.38nm、0.28nm。SEM分析表明LSMO薄膜表面平整、光滑致密。电学测试La1-xSrxMnO3/Si异质结的I-V特性曲线表明,随着Sr掺杂量的增加,同一偏压下的开启电压变小,当电压大于10V时,La1-xSrxMnO3/Si异质结的电流迅速增大,呈现传统的p-n结特征。     

涂料型La1-xSrxMnO3智能热控涂层的研究

以固相反应法制备了高纯度La0.8Sr0.2MnO3粉体,并以其为基料,磷酸二氢铝为粘结剂,采用涂覆工艺在铝基片上制备了涂料型La0.8Sr0.2MnO3热控涂层.采用XRD、EDS对La0.8Sr0.2MnO3粉体的成分进行了表征,用稳态卡计法测量了涂层在100~100℃温度区间内热辐射率随温度的变化,并测量了涂层的太阳吸收比.研究结果表明:粉体合成过程中,经过1200℃三次热处理制备的La0.8Sr0.2MnO3粉体纯度高,合成的粉体具有均匀的微米级粒径尺寸.通过适当调整浆料中La0.8Sr0.2MnO3粉体所占质量百分比,获得辐射率变化范围大于0.3的热控涂层,该性能与采用烧结工艺制备的La0.8Sr0.2MnO3陶瓷片材料在变温条件下的辐射率变化范围接近.该涂层在航天器热控技术中具有潜在的应用前景.     

Ag／La0.67Sr0.33MnO3/Pt异质结构的电阻开关特性

采用脉冲激光沉积技术在Pt／Ti／SiO2／Si（100）衬底上制备出多晶La0.67Sr0.33MnO3（LSMO）薄膜,对其电脉冲致非挥发可逆电阻开关特性进行研究．结果表明,Ag/LSMO／Pt结构具有明显的室温电脉冲诱发电阻开关特性,且在宽电压脉冲作用下表现出较低的开关电压和较快的变阻饱和速度．由此可见,总脉冲能量或电荷（电流作用）为该结构的电阻开关效应提供驱动力．对Ag／LsMO／Pt结构进行了耐久性测试,表明该结构具有良好的疲劳特性与保持特性,可应用于新型不挥发存储器、传感器及可变电阻等电子元器件的研制     

多铁性BaTiO3/La2/3Sr1/3MnO3复合薄膜的制备及其强磁电效应的研究

使用脉冲激光沉积技术,在(001)取向的LaAlO3(LAO)单晶基片上外延生长了BaTiO3/La2/3Sr1/3MnO3(BTO/LSMO)双层复合薄膜.电学和磁学性能的研究显示复合薄膜具有较低的相对介电常数(εr=263),优良的铁电和铁磁性能以及高于室温的铁磁居里温度(Tc=317 K).复合薄膜的磁电电压系数(αE)为176 mV/A,高于同类结构磁电系统一个数量级,相应的界面耦合系数k值为0.68,表明铁磁层和铁电层界面之间存在较大程度的耦合.     

SnO2:F沉积的La0.67Sr0.33MnO3薄膜的电阻开关特性研究

采用脉冲激光沉积技术在SnO2:F(FTO)衬底上制备了La0.67 Sr0.33 MnO3( LSMO)薄膜.室温下利用直流电压对Au/LSMO/FTO三明治结构的器件进行了电化学测试.结果显示样品具有明显的双极性电阻开关性能.通过对I-V特性曲线进行分析,认为在高阻态时肖特基势垒和空间电荷限制电流输运机制调控.在高场区,电阻开关的高低阻态现象由电子陷阱中心分布的不对称引起的空间电荷限制电流理论来解释.     

Growth of La0.7Sr0.3MnO3 films on Si(0 0 1) using SrMnO3 template layer

Using RF magnetron sputtering, we have successfully grown (1 1 0) orientated La_0.7Sr_0.3MnO₃ (LSMO) films on Si(0 0 1) wafers using SrMnO₃ (SMO) as a template layer. The X-ray diffraction (XRD) patterns of the SMO/Si heterostructures indicate that SMO grows along the (1 1 0) orientation, the orientation relationship between the SMO thin film and the Si (0 0 1) substrate being given by (0 1 1)_SMO∣∣(0 0 1)_Si and [01]_SMO∣∣[0 1 0]_Si. From the XRD patterns of the LSMO/SMO/Si heterostructures, we find that with an increase of substrate temperature, the required thickness of SMO, which plays an effective role of tuning the preferential orientation of LSMO, will decrease at first and then increase. It is thought that this originates from the fact that the crystallization of SMO is not perfect at low temperatures whereas too high a temperature results in reaction and diffusion at the interface of the two layers.     

Magnetic properties of NiFe2O4 thin films grown on La0.7Sr0.3MnO3-buffered Si substrate

Nickel ferrite NiFe₂O₄ (NFO) thin films have been prepared on a Si substrate (NFO/Si) and La_0.7Sr_0.3MnO₃ (LSMO)-coated Si (100) substrate (NFO/LSMO/Si) by RF magnetron sputtering. The microstructures and magnetic properties of the two films were systematically investigated. X-ray diffraction (XRD) and atomic force microscopy (AFM) revealed that highly (331)-oriented NFO films with a smooth surface were grown on the LSMO/Si substrate. The magnetization of the films was measured at room temperature. It showed a clear hysteresis loop in both samples, with the magnetic field applied in the plane. However, no hysteresis loop is seen with the magnetic field applied perpendicular to the film plane. This indicates the presence of an anisotropy favoring the orientation of the magnetization in the direction parallel to the film plane. A study of magnetization hysteresis loop measurements indicates that the LSMO buffer layer may improve the magnetic properties of NFO thin films, and that the saturation magnetization increases from 4.15 × 10⁴ to 3.5 × 10⁵ A/m.     

Magnetic properties of NiFe2O4 thin films grown on La0.7Sr0.3MnO3-buffered Si substrate

Nickel ferrite NiFe₂O₄ (NFO) thin films have been prepared on a Si substrate (NFO/Si) and La_0.7Sr_0.3MnO₃ (LSMO)-coated Si (100) substrate (NFO/LSMO/Si) by RF magnetron sputtering. The microstructures and magnetic properties of the two films were systematically investigated. X-ray diffraction (XRD) and atomic force microscopy (AFM) revealed that highly (331)-oriented NFO films with a smooth surface were grown on the LSMO/Si substrate. The magnetization of the films was measured at room temperature. It showed a clear hysteresis loop in both samples, with the magnetic field applied in the plane. However, no hysteresis loop is seen with the magnetic field applied perpendicular to the film plane. This indicates the presence of an anisotropy favoring the orientation of the magnetization in the direction parallel to the film plane. A study of magnetization hysteresis loop measurements indicates that the LSMO buffer layer may improve the magnetic properties of NFO thin films, and that the saturation magnetization increases from 4.15 × 10⁴ to 3.5 × 10⁵ A/m.     

Growth and characterization of La5/8Sr3/8MnO3 thin films prepared by pulsed laser deposition on different substrates

Colossal magnetoresistance La_5/8Sr_3/8MnO₃ (LSMO) thin films were directly grown on MgO(100), Si(100) wafer and glass substrates by pulsed laser deposition technique. The films were characterized using X-ray diffraction (XRD), field emission-scanning electron microscope and atomic force microscopy (AFM). The electrical and magnetic properties of the films are studied. From the XRD patterns, the films are found to be polycrystalline single-phases. The surface appears porous and cauliflower-like morphology for all LSMO films. From AFM images, the LSMO films deposited on glass substrate were presented smooth morphologies of the top surfaces as comparing with the films were deposited on Si(100) and MgO(100). The highest magnetoresistance (MR) value obtained was ?17.21 % for LSMO/MgO film followed by ?15.65 % for LSMO/Si and ?14.60 % for LSMO/Cg films at 80 K in a 1T magnetic field. Phase transition temperature (T_P) is 224 K for LSMO/MgO, 200 K for LSMO/Si and above room temperature for films deposited on glass substrates. The films exhibit ferromagnetic transition at a temperature (T_C) around 363 K for LSMO/MgO, 307 K for LSMO/Si and 352 K for LSMO/Cg thin film. T_C such as 363 and 352 K are the high T_C that has ever been reported for LSMO films deposited on MgO substrate with high lattice mismatch parameter and glass substrates with amorphous nature.     

Pulsed laser deposition of epitaxial ferroelectric Pb(Zr,Ti)O3 films on silicon substrates

We report on the epitaxial growth and electrical properties of Pb_0.52Zr_0.48TiO₃ (PZT) thin films deposited by Pulsed Laser Deposition (PLD) on SrTiO₃ (STO)-buffered Si(001). Previously to PZT growth, 40 nm-thick (La,Sr)MnO₃ (LSMO) layer was deposited to serve as electrical bottom electrode. The 200 nm-thick PZT film epitaxy was optimized by PLD on STO-buffered Si(001).The high contrast of stable artificially poled ferroelectric surfaces evidences the good ferroelectric properties of the PZT thin film. The structural as well as the physical properties of the PZT/LSMO/STO/Si(001) structure prove that very good quality layers have been obtained for films grown on silicon substrate.     

Influence of Interfacial LSMO Nanoparticles/Layer on the Vortex Pinning Properties of YBCO Thin Film

YBa₂Cu₃O_7?δ (YBCO) thin films have been deposited on bare and La_0.67Sr_0.33MnO₃ (LSMO) modified single crystal SrTiO₃ (STO) substrates. The effect of randomly distributed ferromagnetic LSMO nanoparticles and a complete LSMO layer, present at STO/YBCO interface, on the superconducting properties of YBCO thin films has been investigated by temperature dependent magnetization studies. The YBCO thin film on LSMO nanoparticles decorated STO substrate shows significant improvement in the critical current density and pinning force density as compared to the YBCO thin film deposited on bare STO substrate and this improvement is more significant at higher applied magnetic field. However, the LSMO/YBCO bilayer showed the improved flux pinning properties only up to a magnetic field of 1.5 T above which it deteriorates. In the case of LSMO/YBCO bilayer, the underlying LSMO layer gives rise to magnetic inhomogeneities due to domain structure, which leads to improved flux pinning properties limited to lower field. However, in the case of LSMO nanoparticles decorated substrate, the presence of LSMO nanoparticles at YBCO/STO interface seems to introduce magnetic inhomogeneities as well as structural defects, which might be acting as correlated pinning sites leading to improved flux pinning properties of the YBCO thin film over a wide range of applied magnetic field.     

Epitaxial La0.7Sr0.3MnO3 thin films on silicon with excellent magnetic and electric properties by combining physical and chemical methods

Half-metallic ferromagnetic La_0.7Sr_0.3MnO₃ (LSMO) represents an appealing candidate to be integrated on silicon substrates for technological devices such as sensors, data storage media, IR detectors, and so on. Here, we report high-quality epitaxial LSMO thin films obtained by an original combination of chemical solution deposition (CSD) and molecular beam epitaxy (MBE). A detailed study of the thermal, chemical, and physical compatibility between SrTiO₃ (STO)/Si buffer layers and LSMO films, grown by MBE and CSD, respectively, enables a perfect integration of both materials. Importantly, we show a precise control of the coercive field of LSMO films by tuning the mosaicity of the STO/Si buffer layer. These results demonstrate the enormous potential of combining physical and chemical processes for the development of low-cost functional oxide-based devices compatible with the complementary metal oxide semiconductor technology.     

Investigation of the composition and electrical properties of gold–H-terminated silicon (111) interface

Experimental studies of the interface between hydrogen-terminated Si(111) and evaporated Au are reported. Auger Electron Spectroscopy (AES) and Scanning Tunneling Microscopy (STM), in ambient conditions, were used to study the composition and electrical (I–V) properties of the Au/Si junction, as a function of Au film thickness. Au films of 5 nm present a rectifying behavior with the tunneling current for negative tip bias. This result is explained by the fact that Si is known to migrate through the Au layer. The I–V measurements point to the fact that enough Si segregates on top of the Au layer to form a reverse diode. It is also shown that the first monolayers of gold chemically bind to the silicon. Such a surface presents electrical metallic properties at this initial stage of gold growth on silicon.     

Effect of Co,Pd and Pt ultra-thin films on the Ni-silicide formation: investigating the sandwich configuration

The effect of Co, Pd and Pt ultrathin films on the kinetics of the formation of Ni-silicide by reactive diffusion is investigated. 50 nm Ni/1 nm X/ 50 nm Ni (X?=?Co, Pd, Pt) deposited on Si(100) substrates are studied using in-situ and ex-situ measurements by X-ray diffraction (XRD). The presence of Co, Pd or Pt thin films in between the Ni layers delays the formation of the metal rich phase compared to the pure Ni/Si system and thus these films act as diffusion barriers. A simultaneous silicide formation (δ-Ni₂Si and NiSi phases) different from the classic sequential formation is found during the consumption of the top Ni layer for which Ni has to diffuse through the barrier. A model for the simultaneous growth in the presence of a barrier is developed, and simulation of the kinetics measured by XRD is used to determine the permeability of the different barriers. Atom probe tomography (APT) of the Ni/Pd/Ni system shows that the Pd layer is located between the Ni top layer and δ-Ni₂Si during the silicide growth, in accordance with a silicide formation controlled by Ni diffusion through the Pd layer. The effect of the barrier on the silicide formation and properties is discussed.

     

PLZST陶瓷衬底上La0.7Sr0.3MnO3薄膜生长及其磁性能和电输运特性研究

采用磁控溅射法在PLZST陶瓷衬底上制备了不同厚度的LSMO薄膜, 并对其微结构、磁性能及电输运特性进行了研究。结果表明, LSMO薄膜具有单一钙钛矿结构, 晶粒均匀, 表面平整, 其中20 nm厚LSMO薄膜粗糙度仅为2.93 nm。在10~300 K温度范围内, LSMO薄膜均具有大的磁电阻效应, 20 nm厚的LSMO薄膜磁电阻温度稳定性优异。随着薄膜厚度的增加, 薄膜的居里温度、金属绝缘体转变温度、磁化强度和导电性能降低。这可能是由于Pb、Sn、Zr等离子扩散进入LSMO薄膜中, 导致MnO₆八面体畸变造成的。