La0.67Ca0.33MnO3—δ薄膜中的巨磁电阻效应

采用直流磁控溅射法在ＺｒＯ２（００１），ＳｒＴｉＯ３（００１），ＬａＡｌＯ３（００１）和ＮｄＧａＯ３（００１）等单昌衬底上成功地制备了Ｌａ０．０７Ｃａ０．３３ＭｎＯ３－δ薄膜。Ｘ－射线衍射结果表明薄膜具有良好的外延性。低温、磁场下的电输过测量上加磁场后，电阻急剧下降，出现负巨磁阻现象，磁阻比ＭＲ＝在室温一为５０％，２２５Ｋ这高达２０００％以上。文中还对径向磁电阻和Ｈａｌｌ电阻的温度和磁场依赖关系作     

稀磁半导体Cd1—xFexTe的巨法拉第效应

在７０－３００Ｋ温度范围内测量研究了组分ｘ为０．０１，０．００３和０．０６的稀磁半导体Ｃｄ１－ｘＦｅｘＴｅ的法拉第旋转与入射光子能量、温度和组分的关系。首次用多振子模型拟合实验结果，获得了布里渊区Γ点的激子能量Ｅ０和Ｌ点的能隙Ｅ１随组分ｘ的变化规律和Ｅ０的温度关系。讨论了Ｆｅ＾＋＋离子内部能级间跃迁对实验结果的影响。     

巨磁电阻薄膜及巨磁电阻随机存储器

介绍了一种基于巨磁电阻效应的全新的磁电子学器件──巨磁电阻随机存储器。     

Si(111)衬底上IBE法外延生长β-FeSi_2薄膜的研究

本文采用质量分析的低能离子束外延法（以下简称IBE法）在Si（111）衬底上外延生长了β-FeSi2薄膜，并进行了X射线衍射测量分析；与扫描电镜配合验证了β-FeSi2外延薄膜的形成．实验结果表明：所得β-FeSi2（101）或（110）面基本平行于Si（111）面，验证了Si（111）上β-FeSi2外延薄膜的形成；并对失配度做了精确的计算；薄膜形貌呈岛屿状分布，同时分析了生长条件对薄膜形貌的影响．     

聚合物先驱溶液法制备La0.67Ca0.33MnOx薄膜

利用聚合物先驱溶液法在SiO2基片上制备了La0.67Ca0.33MnOx薄膜，用X－射线衍射仪分析的薄膜结晶情况表明了材料是一种多晶薄膜。用标准四探针法测量了薄膜的庞磁电阻效应性能。发现用这种方法在SiO2基片上制得的薄膜在234K左右和5．5T时的磁电阻MR达到了44％，结果表明这种方法能够在普通SiO2基片上制备出具有应用价值的巨磁阻薄膜。     

Ta2O5薄膜的制备及其应用

本文阐述了Ta_2O_5薄膜的各种制备工艺、生长机理及其应用,用超薄Ta_2O_5膜制作的电容器电容量大、可靠性高,这种电容器用于双极式高速存储元件时,可使该元件面积减小到普通元件的1/3,它工作时最长存取时间<5ns。用溅射沉积的Ta_2O_5膜作光波导时,其光传输损耗<1dB/cm。采用S枪结构的磁控溅射技术制备的Ta_2O_5膜光反射率很小,透射率很大且光吸收系数低。它是一种优良的太阳能电池用抗反射(AR)涂层材料。X-轴取向Ta_2O_5膜是一种新型压电材料,用它制作的SAW器件温度稳定性好。另外,Ta_2O_5膜已用于制作湿敏、离子敏元件。     

聚合物先驱溶液成膜烧结法制备La0.67Ca0.33MnOx薄膜

采用了聚合物先驱溶液成膜烧结法在LaALO3单晶上制备了La0.67C0.33MnOx巨磁电阻薄膜。用X－射线衍射仪分析发现，在适当条件下薄膜结晶情况类似于用PLD法制备出的外延薄膜。用标准四探针法测量了薄膜的CMR性能。发现用该法制得的薄膜具有很大的庞磁阻（CMR）效应，并且发现不同的工艺条件如烧结温度对薄膜的CMR效应有很大影响，为化学法制备La0.67C0.33MnOx薄膜提供了有用参考。     

FeCuNbCrSiB薄膜的制备及其巨磁阻抗效应研究

采用磁控溅射方法,在玻璃基片上制备了非晶的Fe73.5Cu1Nb3Cr0.5Si13B9薄膜及三明治结构M/C/M(M为Fe73.5Cu1Nb3Cr0.5Si13B9;C为Cu)的多层膜。在频率(1~40)MHz下,研究了薄膜材料的巨磁阻抗(GMI)效应随外加磁场的变化关系。结果表明:单层膜的GMI效应较小,只有4.4%;而三明治结构多层膜的GMI效应,比单层膜有较大幅度的提高,在5MHz、120Oe下,纵向和横向GMI效应分别达–17.4%和–20.7%。薄膜材料的纵向GMI效应随外加磁场变化呈现先增后减,而横向GMI效应随外加磁场的增加而单调递减,其变化规律与薄膜的易轴取向有很大关系。     

Rectifying,giant magnetoresistance,spin-filtering,newgative differential resistance,and switching effects in single-molecule magnet Mn(dmit)2-based molecular device with graphene nanoribbon electrodes

By applying the density functional theory and the nonequilibrium Green’s function formalism, we investigate the spin transport properties of a single-molecule magnet Mn(dmit)₂ sandwiched between two ferromagnetic zigzag-edge graphene nanoribbon electrodes. The results show that the system can present large rectifying, giant magnetoresistance, spin-filtering and negative differential resistance effects with the help of magnetic field modulation. Moreover, an improved switching effect can also be realized by changing the orientation between planes of two dmit ligands. Therefore, the system will provide the possibilities for a multifunctional molecular device design.     

Preparation of lateral spin-valve structure using doped conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)

To perform four-terminal nonlocal spin-valve measurements on organic spin-valves, we fabricated lateral spin-valve devices consisting of doped conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) [PEDOT:PSS] and ferromagnetic Ni₈₀Fe₂₀ narrow line (width: 530 nm) electrodes. Although the formula of the nonlocal magnetoresistance with the parameters of doped conducting polymers predicts sufficient nonlocal magnetoresistance, we could not observe any spin signal. The spin diffusion length in the doped PEDOT:PSS device does not appear to be as long as those predicted by both the Elliott–Yafet mechanism and the theory of spin relaxation in organic disordered solids.     

New BETS salts based on magnetic (CuCl3, FeCl4) and non-magnetic (GaCl4) anions

New BETS salts (where BETS is bis(ethylenedithio)tetraselenafulvalene) with (CuCl₃)_x, Cu₂C₆, Cu₄Cl₈ and Fe_0.75Ga_0.25Cl₄ anions have been obtained. The crystal structures and electrical and magnetoresistance properties of K-BETS₄Cu₄Cl₈, θ-BETS₄Cu₂Cl₆ and K-BETS₂Fe_0.75Ga_0.25Cl₄ have been studied. The last two compounds have been found to exhibit Shubnikov-de Haas and angle-dependent magnetoresistance oscillations. © 1997 John Wiley & Sons, Ltd.     

Monolithic integration of Giant Magnetoresistance (GMR) devices onto standard processed CMOS dies

Giant Magnetoresistance (GMR) based technology is nowadays the preferred option for low magnetic fields sensing in disciplines such as biotechnology or microelectronics. Their compatibility with standard CMOS processes is currently investigated as a key point for the development of novel applications, requiring compact electronic readout. In this paper, such compatibility has been experimentally studied with two particular non-dedicated CMOS standards: 0.35 μm from AMS (Austria MicroSystems) and 2.5 μm from CNM (Centre Nacional de Microelectrònica, Barcelona) as representative examples. GMR test devices have been designed and fabricated onto processed chips from both technologies. In order to evaluate so obtained devices, an extended characterization has been carried out including DC magnetic measurements and noise analysis. Moreover, a 2D-FEM (Finite Element Method) model, including the dependence of the GMR device resistance with the magnetic field, has been also developed and simulated. Its potential use as electric current sensors at the integrated circuit level has also been demonstrated.     

Photoinduced negative magnetoresistance in 6,13-bis(triisopropylsilylethynyl)-pentacene field-effect transistors

We report on photoinduced negative organic magnetoresistance in low external magnetic-fields (<100 mT) in 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-Pentacene) field-effect transistors. An external magnetic field does not influence the dark current of our device. In contrast, there is a significant increase in photocurrent when magnetic field is applied to the irradiated device, which leads to negative magnetoresistance. The magnetoresistance and photoresponse values are strongly correlated and both are influenced by applied voltages and irradiation intensity. We attribute the observed photoinduced negative magnetoresistance in TIPS-Pentacene field-effect transistors to the presence of electron-hole pairs under irradiation. The overall dissociation probability of electron-hole pairs rises under the influence of an external magnetic field, which leads to a higher number of free charge carriers.     

分子束外延Pb1—xEuxTe材料的红外透射谱研究

在2.5～25μm范围内测量了分子束外延(MBE)Pb_(1-x)Eu_xTe薄膜材料(x=0,0.011,0.032,0.045)的室温红外透射谱,得到了折射率的色散关系及禁带宽度与组份x的关系,首次报道了禁带宽度与光学介电常数的经验公式,讨论了本文结果与其它报道的不同之处。     

厚度依赖的Poly(3-hexylthiophene)光伏器件中的磁场效应

对poly(3-hexylthiophene)(P3HT)光伏器件产生正、负向磁场效应的原因进行了研究。制作了不同活性层厚度的光伏器件,光电流的磁场效应对厚度的依赖非常明显:在活性层厚度为44nm时,有2.8%的正效应;当活性层厚度提高为105nm时,磁场效应变为负值(-5.2%)。为了研究产生这种效应的原因,制备了1-(3-methyloxycarbonyl)propyl-1-phenyl[6,6]C61(PCBM)与P3HT共混的器件。在共混器件中,磁场效应随着PCBM比例的提升而逐渐下降直至湮灭且磁场效应不再随活性层厚度发生变化。磁场效应的产生源于磁场可以调控单线态和三线态激子的比例,进而调节单线态激子主导的激子分离作用和三线态激子主导的激子-电荷分离作用。实验结果显示出在纯P3HT光伏器件中,当PCBM加入到活性层中时,大量激子在给受体界面处分离成为自由载流子,单线态和三线态激子都可以高效地通过激子分离使光电流增强,激子比例不再影响光电流大小,所以磁场效应逐渐消失且对活性层厚度失去依赖。     

液相外延生长Hg_（1－x）Cd_xTe薄膜及其特性分析

报道了用液相外延技术生长Ｈｇ１－ｘＣｄｘＴｅ薄膜的工艺及分析薄膜特性的方法．结果表明Ｈｇ气压、过冷度、降温速率及退人条件等因素对波相外延薄膜的性能有很大影响．由Ｘ射线双晶回摆曲线可定量分析点阵失配度及外延层的组份，由红外透射光谱确定外延层组份的纵向分布．     

SrCoO_(3–δ)陶瓷材料的导电机理和低温热敏特性

用固相反应法合成了可在液氦(4.2K)温度下使用的、非化学计量结构氧化物SrCoO3–δ热敏电阻材料,用XRD、SEM对其进行了表征,同时还测试了低温条件下的电阻值,分析了材料的导电机理和磁阻特性。测试结果表明:材料的B值为35K左右,与在液氢(20K)温度下使用的热敏电阻元件参数(B=300K)比较,SrCoO3–δ热敏材料可在液氦(4.2K)温度下使用。