Ag/Fe/Ag 纳米颗粒膜磁特性和微结构

"利用对靶磁控溅射法制备了一系列Ag/Fe/Ag纳米薄膜,沉积态样品Fe层厚度固定为35 nm,Ag层厚度为1、2、3、4、5 nm．随后对沉积态样品进行了退火处理,退火温度分别为200、300、400、500、600 ℃ , 退火30 min． 利用VSM测量了样品的磁特性, 利用SPM观察样品表面形貌和磁畴结构,并且利用XRD分析了样品的晶体结构．研究结果表明,沉积态样品随Ag层厚度的变化,垂直和平行膜面矫顽力均先增加后减小．当Ag层厚度为3 nm时,垂直膜面矫顽力最大约为260 Oe,样品颗粒分布均     

MgO/Pt界面对增强Co/Ni多层膜垂直磁各向异性及热稳定性的研究

采用直流磁控溅射法在玻璃基片上制备了Pt底层和MgO/Pt双底层的Co/Ni多层膜样品, 通过反常霍尔效应研究了不同MgO厚度和退火温度对样品垂直磁各向异性(perpendicular magnetic anisotropy, PMA)的影响. 随着底层中MgO厚度的逐渐增加, 样品的矫顽力也随之增强, 霍尔电阻变化不大; 对样品进行退火处理后发现, 单纯Pt底层的Co/Ni多层膜随着退火温度的升高, 霍尔电阻逐渐降低, 矫顽力则迅速降低, 热稳定性较差; 而当MgO/Pt双底层的样品在200 ℃退火后矫顽力大幅增加, 霍尔电阻略微有所减小, 更高的退火温度使得Co和Ni合金化, 导致多层膜的PMA特征减弱.     

分子束外延生长Fe/Fe_(50)Mn_(50)双层膜的交换偏置

利用表面磁光克尔效应和铁磁共振对分子束外延生长的Fe/Fe50Mn50双层膜的交换偏置场和矫顽力进行了研究,实验结果表明,当反铁磁层厚度小于5.5!nm时,不出现交换偏置,而当大于这一厚度时,出现交换偏置;大约在7!nm时,达到极大值.随着反铁磁层厚度的继续增大,偏置场和矫顽力随Fe50Mn50膜厚的增大而下降.铁磁共振实验结果表明样品的磁性存在单向各向异性.并对上述结果进行了讨论.     

基于纳米压痕法的多孔硅硬度及杨氏模量与微观结构关系研究

采用电化学腐蚀制备多孔硅，利用场致发射扫描式电子显微镜(field emission scanning electron microscope，FESEM)观测多孔硅的二维微观形貌，利用Nano Indenter XP中的纳米轮廓扫描仪组件(nano profilometry, NP)得到其三维拓扑分析图像，分析了微观结构差异的原因并讨论了多孔硅内部微观结构对其机械性能的影响；利用MTS Nano Indenter XP纳米压入测量仪器，研究了多孔硅的显微硬度和杨氏模量随压入深度的变化规律，比较了不同孔隙率多孔硅的机械性能差别.实验结果测得40mA/cm²，60mA/cm²，80mA/cm²和100mA/cm²四个不同腐蚀电流密度条件下制备多孔硅样品的孔隙率在60%—80%范围内，孔隙率随着腐蚀电流密度的增加而增大；在氢氟酸(HF)浓度为20%的条件下制备出多孔硅样品的厚度在40μm—50μm范围内；测得多孔硅的平均硬度、平均杨氏模量分别在0.478GPa—1.171GPa和10.912GPa—17.15GPa范围内，并且其数值随腐蚀电流密度的增加而减小，在纳米硬度范围内随压入深度的增加而减小，在显微硬度范围内其数值保持相对恒定，分析了样品表面、厚度、微观结构，及环境对其机械性能的影响，得到了多孔硅力学性能随其微观尺度形貌的变化规律. 关键词： 多孔硅 微观结构 硬度 杨氏模量     

电致发光色纯性增强的硅基有机微腔

报道了硅基有机微腔的电致发光（EL）.该微腔由上半透明金属膜、中心有源多层膜和多孔硅分布Bragg反射镜（PS DBR）组成.半透明金属膜由Ag（２０nm）构成，充当发光器件的负电极和微腔的上反射镜.有源多层膜由Al (1 nm) / LiF(05 nm) /Alq3/Alq3:DCJTB/NPB/CuPc/ITO/SiO2组成，其中的Al/LiF为电子注入层，ITO为正电极，SiO2为使正、负电极电隔离的介质层.该PS DBR是采用设备简单、成本低廉且非常省时的电化学腐蚀法用单晶Si来制备的；该PS 关键词： 电化学腐蚀 电致发光 窄峰发射 硅基有机微腔     

Al掺杂ZnO薄膜的厚度对其结构及磁学性能的影响

采用直流磁控共溅的方法在玻璃基底上制备了不同厚度的Al掺杂ZnO薄膜,并在真空和空气中分别退火.利用X射线衍射仪(XRD)和物理性能测量仪(PPMS)对系列薄膜的结构和磁性进行了表征.XRD结果显示:随着膜厚的增加,晶粒尺寸逐渐增大,薄膜的内应力逐渐减小.在空气退火的薄膜样品中观察到了室温的铁磁性,薄膜的饱和磁化强度M_s 随着膜厚的增加而增大,而矫顽力H_c却随着膜厚的增加而减小. 关键词： Al掺杂ZnO薄膜 薄膜厚度 应力 铁磁性     

金属/多孔硅/单晶硅(M/PS/Si)微结构的电学特性

采用双槽电化学腐蚀法制备多孔硅层,然后在多孔硅表面沉积形成金属电极,制备出M/PS/Si微结构.利用SEM分析多孔硅的表面形貌,通过测试其I-V特性分析M/PS/Si微结构的电学特性.结果表明:由Pt做电极形成的M/PS/Si结构,表现出非整流特性.M/PS/Si结构的I-V曲线由线性区和非线性区组成,多孔硅孔隙率越高的M/PS/Si结构的I-V特性曲线线性区越宽.由Cu做电极形成的M/PS/Si结构,表现出整流特性.其整流比随多孔硅孔隙率增加而减小. 关键词： M/PS/Si微结构 孔隙率 I-V特性')" href="#">I-V特性 欧姆接触     

电化学制备薄黑硅抗反射膜

采用计算机控制电流密度按指数规律衰减对单晶硅进行电化学腐蚀,得到了折射率随薄膜厚度连续均匀变化的抗反射膜,即黑硅样品. 这种在制取上快速、经济和工艺非常简单的样品,不仅在较宽波段范围内反射率小于5%,且整个薄膜厚度不足1μm. 利用传输矩阵方法对黑硅样品的反射谱进行模拟,得到了理论与实验符合较好的结果. 关键词： 多孔硅 折射率 抗反射膜 黑硅     

n型有序多孔硅基氧化钨室温气敏性能研究

利用电化学腐蚀方法制备了n型有序多孔硅, 并以此为基底用直流磁控溅射法在其表面溅射不同厚度的氧化钨薄膜. 利用X射线和扫描电子显微镜表征了材料的成分和结构, 结果表明, 多孔硅的孔呈柱形有序分布, 溅射10 min的WO₃薄膜是多晶结构, 比较松散地覆盖在整个多孔硅的表面. 分别测试了多孔硅和多孔硅基氧化钨在室温条件下对二氧化氮的气敏性能, 结果表明, 相对于多孔硅, 多孔硅基氧化钨薄膜对二氧化氮的气敏性能显著提高. 对多孔硅基氧化钨复合结构的气敏机理分析认为, 多孔硅和氧化钨薄膜复合形成的异质结对良好的气敏性能起到主要作用, 氧化钨薄膜表面出现了反型层引起了气敏响应时电阻的异常变化. 关键词： 有序多孔硅 氧化钨薄膜 二氧化氮 室温气敏性能     

Fe含量和粒径对Fe/Cu颗粒膜结构和磁性的影响

采用共蒸发法制备不同组分的Fe/Cu颗粒膜,将样品分两组进行退火和不退火处理. 根据测量及分析,确定了不同成分的Fe/Cu颗粒膜的相组成和晶体结构;找出了 Fe/Cu颗粒膜矫顽力与粒径的关系,利用此关系由自发形核理论可知,提高功率,快速蒸镀薄膜,可得到细密颗粒的Fe/Cu颗粒膜,从而降低矫顽力,减少磁滞损耗.     

Structure and photoluminescence properties of ZnS films grown on porous Si substrates

ZnS films were deposited on porous silicon (PS) substrates with different porosities. With the increase of PS substrate porosity, the XRD diffraction peak intensity decreases and the surface morphology of the ZnS films becomes rougher. Voids appear in the films, due to the increased roughness of PS structure. The photoluminescence (PL) spectra of the samples before and after deposition of ZnS were measured to study the effect of substrate porosity on the luminescence properties of ZnS/PS composites. As-prepared PS substrates emit strong red light. The red PL peak of PS after deposition of ZnS shows an obvious blueshift. As PS substrate porosity increases, the trend of blueshift increases. A green emission at about 550 nm was also observed when the porosity of PS increased, which is ascribed to the defect-center luminescence of ZnS. The effect of annealing time on the structural and luminescence properties of ZnS/PS composites were also studied. With the increase of annealing time, the XRD diffraction peak intensity and the self-activated luminescence intensity of ZnS increase, and, the surface morphology of the ZnS films becomes smooth and compact. However, the red emission intensity of PS decreases, which was associated with a redshift. White light emission was obtained by combining the luminescence of ZnS with the luminescence of PS.     

Magnetization reversal of ultrathin Fe film grown on Si（111） using iron silicide template

Ultrathin Fe films were epitaxially grown on Si（lll） by using an ultrathin iron silicide film with p（2 × 2） surface reconstruction as a template. The surface structure and magnetic properties were investigated in situ by low energy electron diffraction （LEED）, scanning tunnelling microscopy （STM）, and surface magneto-optical effect （SMOKE）. Polar SMOKE hysteresis loops demonstrate that the Fe ultrathin films with thickness t 〈 6 ML （monolayers） exhibit perpen-dicular magnetic anisotropy. The characters of M-H loops with the external magnetic field at difference angles and the angular dependence of coercivity suggest that the domain-wall pinning plays a dominant role in the magnetization reversal process.[第一段]     

Ion-beam induced changes in magnetic and microstructural properties of thin iron films

Changes in magnetic and structural properties of 60–82 nm iron films induced by heavy-ion implantation were studied using the magneto-optical Kerr effect, M?ssbauer spectroscopy, Rutherford backscattering spectroscopy, X-ray diffraction, and X-ray absorption fine structure. The influence of ion-beam parameters (ion mass, fluence) and of sample parameters (external magnetic field and stress during implantation) were investigated. The Fe films, some of them containing a thin ⁵⁷Fe marker layer for M?ssbauer spectroscopy, were deposited on Si(100) substrates, by electron-beam and effusion-cell evaporation. The films were irradiated with ²⁰Ne, ⁵⁶Fe, ⁸⁶Kr and ¹³²Xe ions at energies chosen so that the implantation profiles peaked near the middle of the Fe films. The as-deposited films were magnetically isotropic and had a high coercivity. After ion implantation, the coercivity decreased and magnetic anisotropy developed. Both changes correlated with a decrease in the internal film stress. External mechanical stress applied during the irradiation had hardly any influence on the magnetic texture, opposite to an external magnetic field applied during or before ion implantation. The results are compared with those obtained for ion-irradiated polycrystalline Ni films and epitaxial Fe films and discussed with respect to the role of radiation-induced extended defects as pinning centers.     

硅纳米线的PEOVD生长研究

本文以硅烷（SiH4）为反应气体,利用等离子体化学气相沉积（PECVD）方法在硅（100）衬底上生长硅纳米晶体、纳米线。应用扫描电镜观察不同条件下生长的样品表面,发现衬底条件对硅纳米结构的影响十分显著。在温度、压强等其它条件相同的情况下,对硅衬底应用Fe^3＋催化剂处理后,呈纳米线状结构生长,而无Fe催化剂涂覆情况下,基本呈纳米晶体状生长,说明催化剂对si纳米线的生成起了重要的促进生长作用。通过进一步研究硅纳米晶体、纳米线的等离子增强化学气相生长机理,发现它们以气-液-固（VLS）机制生长。     

Crystal structure and magnetic properties of SmCo-based films deposited on hot Si (1 0 0) substrates

SmCo-based films were deposited on Si (1 0 0) substrates by the rf magnetron sputtering process. The growth conditions are improved for the films deposited on hot Si substrates without the annealing process. The dependence of crystal structure and intrinsic coercivity on substrate temperature is chiefly investigated. It is suggested that TbCu₇ type structural films can be obtained with enhanced in-plane magnetic properties with proper substrate temperature.     

Thermal annealing of FePt thin films by millisecond plasma arc pulses

A series of 20 and 100 nm Fe₅₃Pt₄₇ thin films sputter-deposited onto Si substrates have been thermally annealed using a pulsed thermal plasma arc lamp. A series of one, three or five pulses were applied to the thin films with widths of either 50 or 100 ms. The microstructure and magnetic properties of these annealed Fe₅₃Pt₄₇ films are discussed according to the various annealing conditions and A1 to L1₀ phase transformation. Upon pulse annealing, the average in-plane grain size of 15 nm (nearly equivalent for both film thicknesses) was observed to increase to values near 20 nm. In general, increasing the pulse width or number of pulses increased the L1₀ order parameter, tetragonality of the c/a ratio and coercivity of the specimen. The exception to this trend was for five pulses at 100 ms for both film thicknesses, which indicated a reduction of the order parameter and coercivity. This reduction is believed to be a result of the interdiffusion of Fe and Pt into the Si substrate and the formation of iron oxide clusters in the grain boundaries characterized by atom probe tomography.     

Reaction and deposition of laser-evaporated iron

Reaction of laser-evaporated iron atom was investigated by Mössbauer spectroscopy and was applied for the production of films. Iron oxide films were produced by laser-deposition of Fe metal and hematite solid onto Al substrates, and the compositions of the films changed depending on the pressure of the O₂ atmosphere and the temperature of the substrates. The spin orientations of α-Fe films deposited by three types of deposition methods were compared. The nuclear spin of iron films produced by deposition of Fe atoms vaporized by resistive heating was perpendicular to the substrate surface, while that of films produced by laser-deposition of Fe was parallel to the substrate surface. The nuclear spins of iron films produced using an arc-plasma-gun were linear orientations along nanometer-sized grooves on the Al substrate surface.     

Enhanced physical properties of porous silicon for improved hydrogen gas sensing

In the current communication, porous silicon samples were prepared by pulsed photoelectrochemical etching using a hydrofluoric acid-based solution. The structural and gas-sensing properties of the samples were studied. Apart from the cycle time T and pause time T_off of the pulsed current, a novel parameter, in the shape of the current named ‘delay time T_d’ was introduced. Our results showed that by optimization of delay time, the porosity of samples can be controlled due to the chemical preparation of silicon surface prior to electrochemical anodization. The fourier-transform infrared measurements of porous silicon (PS) layers on Si substrate showed that the typical PS surface was characterized by chemical species like Si–H and Si–O–Si terminations. The two-minute delay before applying electrical current was considered sufficient for the fabrication of higher porosity (83%), more uniform, and more stable structures. The photoluminescence (PL) peak of the optimized sample showed higher intensity than the other samples. An obvious PL blue shift also revealed a change in the crystallographic characteristics of silicon due to quantum confinement effects. Metal–semiconductor–metal diodes with Schottky contacts of nickel were fabricated on PS samples and the potential application of optimized substrates for the improved sensitivity, stability, response time and recovery time of hydrogen gas sensors was subsequently studied.     

Temperature dependence of the surface anisotropy of Fe ultrathin films on Cu(001)

We report an experimental approach to separate temperature dependent reversible and irreversible contributions to the perpendicular magnetic anisotropy of Fe films grown at low temperatures on Cu(001) substrates. The surface anisotropy K(S)(T) is found to decrease linearly with temperature, causing a thermally induced spin reorientation into the plane. The irreversible shift of the spin reorientation transition and the coercivity of the iron films are directly correlated to the increasing Fe island size during annealing. The increased coercivity is discussed in terms of domain wall energy inhomogeneities provided by the islands.