(Ni0.81Fe0.19)66Cr34缓冲层对Ni74Co26薄膜各向异性磁电阻的影响

用磁控溅射方法制备了以Ta和非磁性(Ni0.81Fe0.19)66Cr34为缓冲层的Ni74Co26薄膜,研究了它们的各向异性磁电阻效应.结果表明用厚度为4.5nm的非磁性(Ni0.81Fe0.19)66Cr34做缓冲层的Ni74Co26薄膜,其各向异性磁电阻(AMR)值比用10nm的Ta做缓冲层的同样厚度的Ni74Co26薄膜的AMR有较大的提高.比如,当Ni74Co26薄膜的厚度为12.5nm时,AMR值能提高43%.X射线衍射(XRD)研究表明缓冲层(Ni0.81Fe0.19)66Cr34与磁性层Ni74Co26有非常接近的晶格常数,因此产生了较大的AMR值.     

Ni81Fe19各向异性磁电阻薄膜的工艺和微结构的研究

在不同本底真空和工作气压下制备了Ta／Ni81Fe19薄膜，并进行了磁性测量和原子力显微镜分析。结果表明较高的本底真空和较低的工作气压下制备的薄膜有较大的各向异性磁电阻值△R／R。其原因是高本底真空和低工作气压导致大晶粒尺寸和低粗糙度。进而降低电子的散射．减小电阻R，增大各向异性磁电阻△R／R。在不同真空度下剞备了(Ni81Fel9)64Cr36／Ni81Fe19薄膜，与以Ta为衬底的薄膜相比，具有更大的各向异性磁电阻值，达到了3．2％，这是国内目前报道的最大值，但它受真空度的影响更大。     

基片表面粗糙度对坡莫合金AMR以及磁性能的影响

利用霍尔离子源轰击Si基片获得了不同表面粗糙度的基片,然后利用磁控溅射方法制备了一系列Ta(5nm)/Ni 80Fe 20(12nm)/Ta(2nm)薄膜样品,重点研究了基片表面粗糙度对薄膜结构和各向异性磁阻效应的影响。采用AFM测量基片的表面粗糙度,采用四探针法测量薄膜的各向异性磁阻效应。研究结果表明,随着基片表面粗糙度的增加,坡莫合金的AMR值显著降低,且ΔH显著增加。     

Ta/NiFe和NiFe/Ta界面反应和"死层"现象的研究

Ta/Ni81Fe19和Ni81Fe19/Ta被广泛应用于磁电阻多层膜结构中。我们发现 ,在Ta/Ni81Fe19/Ta薄膜结构中 ,磁性“死层”的厚度大约为 1 6± 0 2nm。用X射线光电子能谱和图谱拟合技术研究Ta/Ni81Fe19和Ni81Fe19/Ta的界面成分和化学状态发现 ,在两上界面处都发生了反应 :2Ta +Ni=NiTa2 ,因此NiFe的有效厚度减少。利用这个反应也可以合理解释用分子束外延制备的自旋阀多层膜比用磁控溅射制备的自旋阀多层膜的“死层”更薄的现象     

热处理时间对NiFe薄膜性能的影响

用磁控溅射法制备了厚度２０－２００ｎｍ的ＮｉＦｅ合金薄膜。研究了热处理时间（及温度）对ＮｉＦｅ薄膜的电阻（电阻率）、各向异性磁电阻比和软磁性能的影响。在一定温度下，经适当时间的热处理可以减小ＮｉＦｅ薄膜的电阻、增大其各和中异性磁电阻比，从而制备出性能较好（各向异性磁电阻比较大、温度稳定性较好）的薄膜磁性材料。     

半导体Si(111)上电沉积NiFe缓冲层薄膜

采用电化学沉积法,在半导体硅片上制备了具有纳米晶粒尺寸的NiFe缓冲层薄膜,并确定了获得Ni80Fe20合金的工艺条件.由SEM形貌观测分析,当薄膜名义厚度＞25 nm时,可形成连续性镀层.I-t暂态曲线及STM结果表明,NiFe薄膜在低过电位下以三维岛状模式生长,在高过电位下以二维层状模式生长,其RMS表面粗糙度最小值仅为0.5 nm.XRD结果表明,薄膜为面心立方Ni基固溶体结构,并具有明显的(111)晶面择优取向.当薄膜组成为Ni80Fe20时,各向异性磁电阻效应(AMR)最大,AMR值为1.8%.     

非均匀退磁场对NiFe薄膜AMR元件性能的影响

采用磁控溅射制备了NiFe各向异性磁电阻(AMR)薄膜,经过光学曝光及离子刻蚀将NiFe薄膜制成了宽度w=20μm、厚度t=20nm、长度l=2.5mm的AMR元件.测量了NiFe元件的磁电阻效应.考虑沿宽度方向退磁场的非均匀性,计算了磁电阻比率.结果表明,理论和实验符合.     

种子层厚度对以NiFeNb为新种子层的坡莫合金薄膜的零场电阻率和AMR的影响

制备了(Ni82Fe18)72.9Nb27.1(dnm)／Ni32Fe18(3nm)／Ta(3mm)坡莫合金系列膜。测量了样品零场电阻率(ρ)．各向异性磁电阻(AMR)和微结构。研究了ρ和AMR随种子层厚度(d)的变化。探讨了d影响ρ和AMR的微观机理。     

退火对NiCo薄膜各向异性磁电阻(AMR)的影响

用磁控溅射法制备了以NiFeCr和Ta分别为缓冲层的两种NiCo薄膜样品,在200、300、400℃温度下对两种样品退火.结果表明,不同的退火温度导致样品AMR值不同,在退火200℃时样品AMR值最大,超过200℃退火磁电阻急剧下降.XRD和摇摆曲线的结果都表明,退火后晶粒的平均晶粒尺寸都会长大,晶内缺陷减少.振动样品磁强计(VSM)测量的结果显示,退火后样品的磁矩有所减小,矫顽力增大,表明缓冲层与NiCo磁薄膜之间有扩散现象.     

半金属 Fe3O4薄膜的制备工艺探索

半金属材料Fe3O4是一种新型的功能自旋电子材料，由于其具有百分之百的自旋极化率而备受关注．但由于铁元素存在多种价态的氧化物，使得制备单一成分的Fe3O4非常困难，因而本文着重对磁控反应溅射制备单一成分的Fe3O4薄膜进行了研究，探索了晶化温度对薄膜结构的影响，并通过引入缓冲层Ta对其性能进行改善，得到了反应溅射制备半金属Fe3O4的最优条件．另外，通过对所制备的Fe3O4薄膜磁电阻效应的测试，发现多晶Fe3O4具有同单晶Fe3O4薄膜类似的负磁电阻效应，因此有望将其应用到自旋电子器件中．     

Interface Reaction of Ta/NiFe and NiFe/Ta and the Dead Layer

The structures of Ta/Ni_(81)Fe_(19) and Ni_(81)Fe_(19)/Ta are commonly used in magnetoresistance multilayers. It is found that the thickness of dead layer in Ta/Ni81Fe19/Ta was about 1.6±0.2 nm. X-ray photoelectron spectroscopy (XPS) was used to study the interfaces of Ta/Ni_(81)Fe_(19) and Ni_(81)Fe_(19)/Ta. The results show that there is a reaction at the two interfaces: 2Ta+Ni=NiTa_2, which caused the thinning of the effective NiFe layer. Furthermore, this reaction could also explain the phenomenon that the dead layer thickness of spin valves multilayers prepared by MBE is thinner than those prepared by magnetron sputtering.     

(Ni0.81Fe0.19)0.66Cr0.34/Ni0.81Fe0.19薄膜的各向异性磁电阻效应及尺寸效应

研究了以非磁性（Ni0.81Fe0.19)0.66Cr0.34薄膜作为过渡层的坡莫合金Ni0.81Fe0.19薄膜的磁电阻效应和饱和磁场，分析退火处理对样品饱和磁场的影响和经刻蚀后的磁电阻效应膜线的尺寸效应，并建立一个统计模型定性分析了其性能变化的机理，计算结果符合实验。     

SiO2层上沉积的纳米多晶硅薄膜及其特性

采用低压化学气相沉积(LPCVD)系统以高纯SiH4为气源,在p型10.16 cm<100>晶向单晶硅衬底SiO2层上制备纳米多晶硅薄膜,薄膜沉积温度为620℃,沉积薄膜厚度分别为30 nm、63 nm和98 nm.对不同薄膜厚度的纳米多晶硅薄膜分别在700℃、800℃和900℃下进行高温真空退火.通过X射线衍射(XRD)、Raman光谱、扫描电子显微镜(SEM)和原子力显微镜(AFM)对SiO2层上沉积的纳米多晶硅薄膜进行特性测试和表征,随着薄膜厚度的增加,沉积态薄膜结晶显著增强,择优取向为<111>晶向.通过HP4145B型半导体参数分析仪对沉积态掺硼纳米多晶硅薄膜电阻I-V特性测试发现,随着薄膜厚度的增加,薄膜电阻率减小,载流子迁移率增大.     

Dependence of GMR on NiFe layer thickness in high sensitive simple spin valve

The dependence of the giant magnetoresistance on Ni/sub 81/Fe/sub 19/ soft magnetic layer thickness is investigated experimentally for a simple spin valve with a top-pinned structure of Ta (6 nm)/Ni/sub 81/Fe/sub 19//Co/sub 90/Fe/sub 10/ (1 nm)/Cu (1.8 nm)/Co/sub 90/Fe/sub 10/ (3.5 nm)/Ir/sub 20/Mn/sub 80/ (8 nm)/Ta (6 nm). With Ni/sub 81/Fe/sub 19/ thickness increased from 6 nm to 7 nm, the magnetoresistance (MR) ratio decreases sharply from 8.34% to 3.34%, whereas it changes only slightly within the thickness ranges from 2-6 nm and from 7-12 nm, and larger MR ratios are obtained in the range from 2-6 nm. For a spin valve with an optimized thickness of Ir/sub 20/Mn/sub 80/ (11 nm) and top Ta (3 nm), the MR dependence is in accordance with the former structure when Ni/sub 81/Fe/sub 19/ thickness changes from 3.5 to 5.5 nm, and an optimized spin valve with 4.5-nm-thick Ni/sub 81/Fe/sub 19/ is obtained. This spin valve has a large MR ratio (9.15%), low coercive force (0.85 Oe), and high sensitivity, which makes it promising for applications.     

Effect of microstructural evolution on magnetic properties of Ni thin films

The magnetic properties of Ni thin films, in the range 20–500 nm, at the crystalline-nanocrystalline interface are reported. The effect of thickness, substrate and substrate temperature has been studied. For the films deposited at ambient temperatures on borosilicate glass substrates, the crystallite size, coercive field and magnetization energy density first increase and achieve a maximum at a critical value of thickness and decrease thereafter. At a thickness of 50 nm, the films deposited at ambient temperature onto borosilicate glass, MgO and silicon do not exhibit long-range order but are magnetic as is evident from the non-zero coercive field and magnetization energy. Phase contrast microscopy revealed that the grain sizes increase from a value of 30–50 nm at ambient temperature to 120–150 nm at 503 K and remain approximately constant in this range up to 593 K. The existence of grain boundary walls of width 30–50 nm is demonstrated using phase contrast images. The grain boundary area also stagnates at higher substrate temperature. There is pronounced shape anisotropy as evidenced by the increased aspect ratio of the grains as a function of substrate temperature. Nickel thin films of 50 nm show the absence of long-range crystalline order at ambient temperature growth conditions and a preferred [111] orientation at higher substrate temperatures. Thin films are found to be thermally relaxed at elevated deposition temperature and having large compressive strain at ambient temperature. This transition from nanocrystalline to crystalline order causes a peak in the coercive field in the region of transition as a function of thickness and substrate temperature. The saturation magnetization on the other hand increases with increase in substrate temperature.     

磁性多层膜的X射线光电子能谱研究

用射频 /直流磁控溅射法制备了NiOx/Ni81Fe19和Co/AlOx/Co磁性薄膜。利用X射线光电子能谱研究了NiOx 对Ni81Fe19耦合交换场Hex与NiOx 化学状态的关系以及Co/AlOx/Co磁性薄膜中AlOx 对Co膜的覆盖状况。结果表明 :Hex的大小只与 2价镍有关 ,单质镍和 3价镍对Hex没什么作用 ;在Co/AlOx/Co磁性薄膜中 ,Al层将Co膜完全覆盖所需要的最小厚度为 2 .0nm ,用角分辨XPS测出的Al氧化厚度为 1 15nm     

低温水浴制备ZnO纳米晶薄膜的研究

首先在低温下制备了粒径小于10nm的ZnO纳米晶,然后采用旋口法制备了ZnO纳米晶薄膜,XRD分析ZnO晶相是纤锌矿结构;SEN与AFM表明,纳米晶薄膜在300℃退火后薄膜的厚度明显地减小到130nm（未退火200nm）,粒径明显增大,表面粗糙度减少到3．27nm（未退火4．89nm）;紫外-可见吸收和透射比光谱表明,随着退火温度的增加,吸收边发生了红移,吸收肩更明显,薄膜具有高的透射率（75—85％）,随着温度增加薄膜方阻增大,300℃以下退火方阻增加很小（小于8．5Ω／sq）,400℃以上退火方阻大幅增加（大于21．1n／sq）,假定存在最优退火温度点（300℃）。     

Oscillatory behavior of the magnetic properties of Nd–Fe–B films with Mo and Mo–Cu additions

A series of Ta/NdFeB/Ta thin films with Mo and Mo–Cu additions embedded by alloying and by stratification have been prepared by r.f. sputtering. The influence of additions, their embedding mode, and annealing temperature on the structural and magnetic behavior of Ta/NdFeB/Ta thin films is presented. The use of additions of Mo and Mo–Cu leads to refined grain structure and improvement in the hard magnetic characteristics of Ta/NdFeB/Ta thin films. The Ta/[NdFeBMo(540 nm)/Ta films and Ta/[NdFeB(180 nm)/MoCu(dnm)] × n/Ta multilayer films present enhanced coercivities and M_r/M_s ratios in comparison with the Ta/NdFeB(540 nm)/Ta films. The stratification of Ta/NdFeB/Ta thin films with Mo–Cu interlayers leads to an oscillatory behavior of hard magnetic characteristics of the Ta/[NdFeB(180 nm)/MoCu(dnm)] × n/Ta multilayer films, when the thickness, d, of Mo–Cu interlayers varies by increments of 1 nm. When the thickness of Mo–Cu interlayers varies by increments of 2 nm the oscillatory behavior of the magnetic characteristics is not revealed. For a thickness of the Mo–Cu interlayer of 3 nm in the Ta/[NdFeB(180 nm)/MoCu(3 nm)] × 3/Ta thin films annealed at 650 °C, the c-axis of part of the hard magnetic Nd₂Fe₁₄B grains is oriented out-of-plane.     

Magnetic properties of oxidized iron thin films grown by sputtering at very low temperatures

Iron thin films have been grown by DC magnetron sputtering using Si(100) wafers as substrates, and then oxidized in a well-controlled oxygen atmosphere in the vacuum chamber. Film thickness is about 50 nm, and grains forming these samples do not exceed 20 nm. In order to control structural properties such as size and shape of these grains, growth conditions can be modified, like deposition rate or substrate temperature, varying from 150 to 300 K. Two sets of samples have been prepared considering deposition rate: (i) films grown at 0.6 nm/min and (ii) at 1.2 nm/min. In order to prevent iron films from natural oxidation, all the sample series were covered with a gold layer. Analysis of their magnetic behaviour shows a strong dependence on grain size and temperature, resulting in a more effective oxidation for samples prepared at higher deposition rates and lower substrate temperatures, which behaves as a Fe/Fe oxide granular system.