La1-xSrxMnO3薄膜的制备、结构及电磁特性

以无机盐为原料,采用溶胶-凝胶工艺在Si衬底上制备La1-xSrxMnO3(LSMO)薄膜,XRD和TEM分析表明LSMO薄膜呈现纳米晶菱形钙钛矿结构,SEM分析表明LSMO薄膜表面平整、光滑致密。磁学测试结果表明:在0T、0.4T和0.8T时薄膜的Tp分别为220K、224K和229K,随着磁场的增大Tp移向高温的同时峰值电阻降低,这与铁磁相变及磁场对DE作用的影响有关。MR极值在250K左右达18.4%。     

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.     

SrMnO3阻挡层对La0.8Sr0.2MnO3/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La0.8Sr0.2MnO3和引入SrMnO3(SMO)阻挡层后沉积La0.8Sr0.2MnO3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.     

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。     

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.     

真空退火La_(0.7)Sr_(0.3)MnO_3薄膜的光诱导特性

用溶胶-凝胶(Sol-gel)法制备La0.7Sr0.3.MnO3(LSMO)靶材,用脉冲激光沉积(PLD)法在LaAlO3a(012)基片上沉积出厚度约为187 nm的LSMO薄膜,研究了真空退火对薄膜的输运和光诱导特性的影响.结果表明,薄膜的相变温度随着退火时间的增加而降低,薄膜的电阻率升高.在低温金属相光照使电阻率降低,在高温绝缘相光照则使电阻率升高.随着退火时间的增加,光电导(△p)先增大而后减小,在真空条件下退火40 min的薄膜光电导(△p)达到最大值为0.013 Ωcm.根据双交换作用解释了薄膜光电导的变化规律.     

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.     

渠道火花烧蚀法制备La0.7Sr0.3MnO3薄膜

采用新型渠道火花烧蚀技术在LaAlO3(001)基片上生长了La0.7S0.3MnO3(LSMO)薄膜.X射线衍射对样品结构的分析表明,制备的LSMO薄膜具有c轴取向生长的特点,薄膜与基片间因晶格不匹配而受面内应力挤压,发生弛豫而出现两相.在室温下采用振动样品磁强计测试样品的面内方向磁滞回线,表明制备的LSMO样品具有软磁性,矫顽力Hc=13 Oe.通过标准四探针法测量了LSMO薄膜的室温薄膜电阻与外加磁场的关系,得知零场电阻率ρ(0)=19.4 mΩ·cm,室温下4800 Oe外场作用下的磁电阻变化率为2.25%,对此用双交换作用机制定性地加以了解释.     

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。     

Pr2/3Sr1/3MnO3薄膜外场诱导自旋输运特性

采用脉冲激光沉积法制备了稀土掺杂钙钛矿锰氧化物Pr2/3Sr1/3MnO3(PSMO)外延薄膜,研究了薄膜在磁场、激光和电流作用下的自旋输运特性.在低温铁磁金属相,激光作用使薄膜的电阻增大,而磁场和电流则诱导电阻减小;在高温顺磁绝缘态,外场诱导均使电阻减小.在铁磁金属相,外场诱导输运特性的变化可归结于外场对体系电子自旋系统的影响:磁场和电流加强材料中eg电子和t2g局域电子间的自旋平行,增强了双交换作用;激光作用可产生光致退磁效应,减弱双交换作用.在顺磁绝缘态,场致电阻降低源于外场致使小极化子的退局域化效应.     

双掺杂稀土锰氧化物La2/3(Ca1/3Sr2/3)1/3MnO3薄膜的输运特性

采用射频磁控溅射法制备了Ca、Sr双掺杂La2/3(Ca1/3Sr2/3)1/3MnO3(LCSMO)薄膜。电阻率-温度特性表明,薄膜在387K时发生铁磁金属相-顺磁非导体相相变。同时测试了薄膜在180,230和280K温度下的伏安特性．表明所制备的薄膜具有自阻效应,并分析了产生该现象的原因。     

(La,Pr)2/3Sr1/3MnO3薄膜激光诱导电阻效应

研究了钙钛矿锰氧化物La2/3Sr1/3MnO3和Pr2/3Sr1/3MnO3单晶薄膜的激光诱导电阻变化特性.低温铁磁金属相,激光诱导使薄膜的电阻增大,而在顺磁绝缘相则电阻减小,同时薄膜的绝缘体-金属相变(IMT)转变温度Tp向低温方向移动.对于Pr2/3Sr1/3MnO3薄膜,当激光功率为22mW时,光致电阻相对变化的最大值约为9.6%.光诱导效应致使薄膜的电阻发生变化,并使其IMT的转变温度点向低温方向移动,主要是由于光子能激发eg向下电子的跃迁,改变体系自旋极化方向.     

Lao.5Sro.5MnO3薄膜的输运特性和光诱导效应

用磁控溅射方法制备了La0.5Sro 5MnO3薄膜,研究了薄膜的输运特性和光诱导效应.La0.5Sr0 5MnO3薄膜具有温度相变特征:低温为铁磁金属相,高温则为顺磁非导体相,相变温度420 K.为铁磁金属相时,光诱导效应导致薄膜的电阻增大,在360 K电阻变化相对值的最大值约为9.62%.根据双交换作用模型,激光导致顺磁非导体相小极化子的浓度增加,使电阻减小.     

不锈钢基Al2O3/SiC双层薄膜的制备和性能

用磁控溅射法在奥氏体不锈钢上分别制备了SiC单层膜和Al2O3/SiC双层膜,研究了溅射气压,溅 射功率以及退火温度对性能的影响.对比了二者的结构、硬度以及耐腐蚀性.结果表明,Al2O3缓冲层降低了SiC薄膜与奥氏体不锈钢基底的热失配和晶格失配,减少了因其而产生的缺陷,从而改善了奥氏体不锈钢上SiC薄膜的结晶质量.     

Cu/Al_2O_3复合薄膜的制备及其抗氧化性能

本文在纺织纤维基材表面采用二次溅射沉积法制备了Cu/Al_2O_3复合薄膜,利用扫描电镜(SEM)、X射线能谱仪(EDX)和矢量网络分析仪对室温环境下存放3600h的复合薄膜的表面形貌、元素含量以及屏蔽效能进行了测试,并与相同工艺条件下制备的纯Cu薄膜进行了对比分析。结果表明:与纯Cu薄膜结构的不稳定性相比,由于复合薄膜表层Al_2O_3薄膜的结构稳定性和致密性,Cu/Al_2O_3复合薄膜在保证高屏蔽性能的前提下,具有整体结构的稳定性,表现出了良好的抗氧化性能。     

Fabrication of resonant-tunneling diodes by Sb surfactant modified growth of Si films on CaF/sub 2//Si

Molecular beam epitaxy growth of Si thin films on CaF/sub 2//Si(111) substrates has been studied. A surfactant-modified solid-phase epitaxy method, where the room temperature Si deposition was followed by annealing under Sb flux, resulted in a continuous, smooth epitaxial crystalline Si film with a sharp (/spl radic/3/spl times//spl radic/3)R30/spl deg/ reconstruction and a surface roughness of 0.15-nm rms for a 2.8-nm Si thin film. This growth technique was used to fabricate CaF/sub 2//Si/CaF/sub 2/ double-barrier resonant tunneling diodes in SiO/sub 2/ windows patterned on Si(111) substrates. A negative differential resistance (NDR) peak was found at /spl sim/0.35 V at 77 K, and the current density at the NDR peak was estimated to be 3-4 orders of magnitude higher than in earlier reports.     

Dendritic flux avalanches in superconducting Nb3Sn films

The penetration of magnetic flux into a thin superconducting film of Nb₃Sn with critical temperature 17.8 K and critical current density 6 MA/cm² was visualized using magneto-optical imaging. Below 8 K an avalanche-like flux penetration in form of big and branching dendritic structures was observed in response to increasing perpendicular applied field. When a growing dendritic branch meets a linear defect in the film, several scenarios were observed: the branch can turn and propagate along the defect, continue propagation right through it, or “tunnel” along a flux-filled defect and continue growth from its other end. The avalanches manifest themselves in numerous small and random jumps found in the magnetization curve.     

Influence of surface modification of alumina on bond strength in Al2O3/Al/Al2O3 joints

The subject of the work was to study the effect of Ti thin film on alumina ceramic on mechanical strength and fracture character of Al₂O₃/Al/Al₂O₃ joints. The joints were formed by liquid state bonding of alumina substrates covered with titanium thin film of 800 nm thickness using Al interlayer of 30μm thickness at temperature of 973 K in a vacuum of 0.2 mPa for 5 min. The bend strength was measured by four–point bending test at room temperature. Scanning and transmission electron microscopy were applied for detailed characterization of interface structure and failure character of fractured joint surfaces. Result analysis has shown that application of the Ti thin film on alumina leads to decrease of bond strength properties of Al₂O₃/Al/Al₂O₃ joints along with the change either of structure and chemistry of interface or of failure character.     

Giant room temperature electric-field-assisted magnetoresistance in La0.7Sr0.3MnO3/n-Si nanotip heterojunctions

An on-chip approach for fabricating ferromagnetic/semiconductor-nanotip heterojunctions is demonstrated. The high-density array of Si nanotips (SiNTs) is employed as a template for depositing La(0.7)Sr(0.3)MnO(3) (LSMO) rods with a pulsed-laser deposition method. Compared with the planar LSMO/Si thin film, the heterojunction shows a large enhancement of room temperature magnetoresistance (MR) ratio up to 20% under 0.5 T and a bias current of 20 μA. The MR ratio is found to be tunable, which increases with increasing external bias and the aspect ratios of the nanotips. Electric-field-induced metallization, in conjunction with nanotip geometry, is proposed to be the origin for the giant MR ratio.     

Temperature-dependent <Emphasis Type="Italic">C-V</Emphasis> characteristics of Au/ZnO/n-Si device obtained by atomic layer deposition technique

Since the importance of Schottkky devices, Au/ZnO/n-Si device were obtained, and the capacitance–voltage (C-V) and conductance-voltage (G-V) characteristics of Au/ZnO/n-Si device were studied using admittance spectroscopy at changing temperature from 160 to 340 K with 20 K intervals and ?1 to +2 V bias voltage range. The interface thin film ZnO layer was deposited on the n-type Si wafer by atomic layer deposition technique (ALD) in order to obtain homogenous interface layer. The layer thickness of ZnO was taken as 10 nm by the resulting ZnO film growth rate at about 1.45 Å per cycle. This thin film layer was characterized with XRD and AFM analyses. It can be seen from the C-V curves of the device that the capacitance values increased in depletion region with increasing temperature and exhibited peaks towards to forward biases after 240 K temperature. The changing of capacitance values confirmed re-ordering and re-structuring of charges in the interface of the device with changing temperature. The G-V curves of the device also increased with increasing temperature and towards to forward bias voltages due to increasing free charges in the interface. The series resistance (\({R}_{s}\)) of the device was taken into account to understand its effect on main electrical parameters, and it could be seen from these results that the \({R}_{s}\) strongly depends on the device temperature. The impedance (Z) values decreased with changing from ?1 to +2 V bias voltages and increasing temperature. The barrier height which was obtained from the C ^?2 -V plots increased a slope of 0.00108 eV/K with a decrease in temperature from 160 to 340 K. It can be concluded that the Au/ZnO/n-Si device may be used and improved for next technological applications such as capacitor and memristor.