L10-FePt纳米颗粒的合成、结构与磁性

首先概述了L10-FePt纳米颗粒的普遍制备方法,然后重点总结了降低其相转变温度和直接合成这两个方面的典型实验方法,并回顾了L10-FePt纳米颗粒结构、磁性能与自组装方面的最新研究进展。     

掺杂Bi促进L10-FePt有序转变的第一性原理研究

掺杂第三元素是促进FePt有序相变和降低有序转变温度的重要方法,元素Bi可大幅度降低有序转变温度,在低温下直接合成出高有序的FePt纳米粒子,但Bi促进FePt有序的机理和有序转变中的作用仍然是一个挑战。本文针对该问题,基于第一性原理密度泛函理论研究了Bi元素对FePt的晶格常数、形成能、差分电荷密度、饱和磁化强度和有序转变温度的影响。结果表明Bi原子取代Fe原子比取代Pt原子的替位形成能更低,Bi原子更容易取代Fe原子。Bi原子取代近邻位的替位形成能要比远邻位的替位形成能更低,Bi原子倾向于在FePt晶格内聚集。Fe原子是FePt体系磁性的主要来源,Bi原子对FePt的电子结构和磁性影响很小。掺杂Bi元素后FePt的有序转变温度明显降低,其中双掺杂情况FePt体系的有序转变温度最低为623.32K。空位机制在有序转变中起主导作用,Bi元素降低了FePt的空位形成能,提高体系中Fe原子和Pt原子的空位浓度并促进Fe原子和Pt原子的扩散和迁移,从而促进FePt有序相变。     

Transparent conductive Sb-doped SnO2/Ag multilayer films fabricated by magnetron sputtering for flexible electronics

The effects of an embedded silver layer and substrate temperature on the electrical and optical properties of Sb-doped SnO₂ (ATO)/silver (Ag) layered composite structures on polyethylene naphthalate substrates have been investigated. The highest conductivity of ATO/Ag multilayer films was obtained with a carrier concentration of 1.5 × 10²² cm^?3 and a resistivity of 2.4 × 10^?5 Ω cm at the optimum Ag layer thickness and substrate temperature. The photopic averaged transmittance and Haacke figure of merit are 81.7%, and 21.7 × 10^?3 Ω^?1, respectively. In addition, a conduction mechanism is proposed to elucidate the mobility variation with increased Ag thickness. We also describe the influence of substrate temperature on the structural, electrical and optical properties of the ATO/Ag multilayer films, and propose a mechanism for the changes in electrical and optical properties at different substrate temperatures.     

Rolling textures in nanoscale Cu/Nb multilayers

Rolling textures in nanoscale multilayered thin films are found to differ markedly from textures observed in bulk materials. Multilayered thin films consisting of alternating Cu and Nb layers with columnar grains were produced by magnetron sputtering, with individual layer thickness ranging from 4 μm to 75 nm and Cu/Nb interfaces locally satisfying the Kurdjumov–Sachs (K–S) orientation relations. After rolling to 80% effective strain, samples with a larger initial layer thickness develop a bulk rolling texture while those with a smaller initial layer thickness display co-rotation of Cu and Nb columnar grains about the interface normal, in order to preserve the K–S orientation relations. The resulting K–S texture has 0 0 1Nb parallel to and 1 1 0Cu approximately 5° from the rolling direction. A crystal plasticity model based on the Principle of Minimum Shear captures the K–S texture approximately and suggests that Nb drags Cu along in the rotation process.     

基片温度对Ni80Fe20薄膜结构和各向异性磁电阻的影响

本文用磁控溅射方法制备出一系列Ni80Fe20磁性薄膜,研究不同基片温度对薄膜结构和各向异性磁电阻的影响.基片温度在150～180 ℃时制备的Ni80Fe20薄膜具有较大的各向异性磁电阻效应和较低的磁化饱和场.X射线衍射仪和扫描电子显微镜测量结果表明,基片温度通过改变薄膜的晶体结构、晶粒大小和均匀性等微观结构改变薄膜的零场电阻率和各向异性磁电阻,文章对实验结果做出了详细分析.     

FePt/Cu多层膜化降低L10-FePt有序化温度

采用直流磁控溅射方法制备FePt／Cu多层膜,再经不同温度下真空热处理得到有序L10-(FePt)100-xCux薄膜．结果表明,Cu的添加可以降低FePt薄膜有序化温度．[FePt(4nm)／Cu(0．2nm)10多层膜在350℃热处理1h后,有序度增至0．6,矫顽力达到421kA／m．对插入极薄Cu层促进有序化在较低的温度下进行的热力学和动力学因素进行了讨论.     

High-coercivity Nd–Fe–B thick films without heavy rare earth additions

The magnetic properties and microstructures of two Nd–Fe–B thick films with different Nd contents have been studied. The films were deposited in the amorphous state and were crystallized by post-deposition annealing. Both films show a strong 〈0 0 1〉 fibre texture out-of-plane. The film with the higher Nd content has a large room temperature coercivity of 2.7 T, while the one with the lower Nd content has a room temperature coercivity of only 0.7 T. The difference in coercivity may be explained by the fact that the film with the higher Nd content exhibits a continuous Nd-rich grain boundary phase, giving better isolation of the Nd₂Fe₁₄B grains with respect to magnetic exchange interactions. The extrusion of Nd-rich liquid to the top surface of the film with high Nd content during post-deposition annealing led to the formation of ripples in the Ta capping layer, indicating that the films are under compressive stress. This stress-induced flow of the Nd-rich material up through the film explains the excellent distribution of the Nd-rich grain boundary phase. Atom probe tomography has revealed the presence of Cu in the Nd-rich grain boundary phase, explaining the formation of the liquid phase at the relatively low temperature of 550 °C due to the eutectic reaction of Nd and Cu.     

Characterization of EB-PVD yttrium-stabilised zirconia by nanoindentation

Nanoindentation was used to determine room temperature Young's modulus and hardness of the top surface and cross section of an electron beam physical vapor deposited yttrium-stabilized zirconia layer. In situ observations of indentations inside a scanning electron microscope (SEM) chamber were used along with normalized cross correlation (NCC) to evaluate the degree to which indentation of a columnar microstructure can be affected by elastic structural deformation. It was found that (i) the top surface Young's modulus is roughly twice that of the cross section. (ii) Upon isothermal heat treatment at 1100 °C for 80 h, an increase in Young's modulus and hardness occurred, to a greater degree in the bottom 20 μm of the cross section, and in the top surface, which was attributed to preferential sintering in these zones. (iii) NCC analysis of SEM observations of nanoindentation in the cross section gave an estimate of the extent to which elastic structural deformation is a constituent of the measured displacement. It was found that depending on the indenter location relative to the columnar microstructure, an underestimation of the Young's modulus by as much as a factor of four can occur.     

室温低压下脉冲等离子体生长立方氮化硼薄膜

运用脉冲高能量密度等离子体,在室温下制成立方氮化硼薄膜．沉积薄膜的衬底材料分别选用单晶硅、氯化钠和ＧＣｒ１５轴承钢,用扫描电镜、透射电镜、红外吸收谱仪、扫描Ａｕｇｅｒ微探针等对沉积的薄膜进行了分析与测试,结果表明,氮化硼薄膜的结构及性质强烈地依赖于实验条件．分析表明立方氮化硼晶核的形成与衬底材料关系不大,但晶核的生长则部分地依赖于衬底．     

衬底温度对Fe-N薄膜结构、形貌及磁性能的影响

采用直流磁控溅射方法,以Ar和N2作为放电气体,在单晶Si(100)衬底上沉积了Fe-N薄膜.采用X射线衍射仪(XRD)、X射线光电子能谱分析仪(XPS)、原子力显微镜(AFM)和超导量子干涉仪(SQUIDS)对所制备的样品进行了结构、成分、形貌和磁性能分析,研究了衬底温度对薄膜的结构、形貌和磁性能的影响.结果表明:衬底温度对Fe-N薄膜的结构有重要的影响,通过控制衬底温度可以获得单相γ′-Fe4N化合物薄膜;γ′-Fe4N具有较高的饱和磁化强度,是非常有应用前景的磁记录介质及磁头功能材料.     

溶胶-凝胶法制备薄膜材料抗高温氧化性能研究

制备了SiO2、ZrO2和添加不同成分的siO2-ZrO2复合溶胶，研究了在Cu／Ni上浸涂不同溶胶后形成膜层的抗高温氧化性能，探讨了不同膜层对Cu／Ni在800℃、900℃C下高温氧化规律的影响。结果表明，这些膜层很好的改善了Cu／Ni的抗高温氧化性能，而且向SiO2-ZrO2复合溶胶中添加铈、钇等稀土元素以及ZrO2纳米粉，可以进一步改善SiO2-ZrO2凝胶膜层的抗高温氧化性能。     

Interface-directed spinodal decomposition in TiAlN/CrN multilayer hard coatings studied by atom probe tomography

Microstructural and compositional changes in TiAlN/CrN multilayered films occurring at temperatures up to 1000 °C were studied at different length scales by a combination of atom probe tomography, transmission electron microscopy and X-ray diffraction. We observe the onset of decomposition of the multilayer structure at 700 °C via the mechanism of interface-directed spinodal decomposition of TiAlN layers, where Al atoms preferentially move toward the nearest interface and segregate there. The interface-directed mechanism later transforms into isotropic spinodal decomposition and is accompanied by intense interdiffusion between the constituting layers. Distinct compositional gradients across columnar grain boundaries (extending perpendicular to the multilayers) are detected at this stage of decomposition. Drastic differences in decomposition behavior across the film depth were observed at elevated temperatures (800–1000 °C): the layered structure completely dissolves in the near-surface part but persists in the regions distant from the surface. The influence of residual stresses caused by the sputter deposition process on the thermally induced evolution of the multilayer thin films is discussed.     

Electrical Properties and Local Domain Structure of LiNbO3 Thin Film Grown by Ion Beam Sputtering Method

The nanocrystalline ferroelectric LiNbO3 films on（001） Si substrates with the random orientation of polycrystalline grains and the predominance of the grains with lateral orientation of the polar axis were grown using the ion beam sputtering method. The remanent polarization and the coercive field are 12 μC/cm2and 29 kV/cm, respectively. The thermal annealing leads to the coarsening of the grains. The appearance of the ＂local texture,＂ which gives rise to the unipolarity of the heterostructures caused by the predominance of the one direction in the vertical component of the spontaneous polarization, is investigated.     

衬底温度对溅射法生长Cu-Al-O薄膜性能的影响

使用多晶CuAlO2陶瓷靶，利用射频磁控溅射法沉积Cu-Al-O薄膜。傅立叶变换红外光谱显示薄膜中存在与CuAlO2相关的Cu-O,Al-O和O-Cu-O键。在可见光范围内Cu-Al-O薄膜具有较好的透过性，衬底温度为400℃～500℃时薄膜透过率在60％-70％之间，计算拟合得到Cu-Al-O薄膜的直接和间接带隙能分别为3．52eV和1．83eV左右，与多晶CuAlO2薄膜结果一致。在近室温区薄膜符合半导体热激活导电机制，其电导率随衬底温度的升高先增大后减小，500℃沉积的薄膜导电性较好，室温电导率达到2．36×10^-3S·cm^-1，这可能源于Cu-Al-O薄膜中与CuAlO2相关的键合形成情况的改善。     

基于Au/Ni-W多层薄膜修饰铜基微纳分级结构固相瞬态焊接方法

目的 以特殊形貌的铜基微纳结构为基板,在其上依次镀覆Ni-W合金层和Au纳米层,在超声能量和室温条件下,实现瞬时与锡基焊料的焊接,解决无铅焊料由于高熔点对薄芯片和热敏器件造成的热冲击和热损伤问题,保证器件安全性和性能可靠性.方法 采用电化学方法沉积出特殊形貌铜基微纳分级结构,在其上化学镀覆层厚为180 nm的Ni-W合金层和50 nm的Au层.将获得的Au/Ni-W多层薄膜修饰的铜基结构与商用焊料(SAC305)在焊接压力98 N(20 MPa)、焊接时间3 s、超声振动3 s条件下实现固相瞬态焊接.将不同表面修饰层的铜基微纳分级结构与焊球进行破坏剪切测试.将焊接后的样品在180℃下分别进行10、30、60 min的时效处理.结果 铜基微米级突起结构高度为2～4μm,底端尺寸为800～1200 nm,具有优良的凸起结构密度和长径比.Au/Ni-W修饰后的铜基微纳分级结构与SAC305焊球所形成的焊接界面嵌入效果好,没有任何孔洞存在,焊接界面平均剪切强度为43.06 MPa.结论 铜基微纳分级结构插入焊球内部形成镶嵌,产生机械互锁,而Au/Ni-W合金修饰层能有效提高铜基微纳分级结构表面硬度,与锡焊料形成较大的硬度差,在插入式焊接中减少了孔洞的形成,焊接效果优良.Ni-W合金层的存在延缓了Cu-Sn之间的互扩散,阻挡了Cu-Sn金属间化合物的生长,减少了因界面失效而产生的可靠性问题.     

热解温度对镧、锰共掺杂铁酸铋薄膜铁电性能的影响(英文)

在不同热解温度下,采用溶胶-凝胶法在Pt/Ti/SiO2/Si衬底上制备镧、锰共掺杂铁酸铋铁电薄膜Bi0.9La0.1Fe0.95Mn0.05O3(BLFMO)。利用热失重仪(TGA)分析BLFMO原粉的质量损失,用 X 射线衍射仪(XRD)和原子力显微镜(AFM)分析 BLFMO 薄膜的晶体结构和表面形貌。在热解温度为420℃时,得到BLMFO薄膜的剩余极化值为21.2μC/cm2,矫顽场为99 kV/cm,漏电流密度为7.1×10-3 A/cm2,说明薄膜在此热解温度下具有较好的铁电性能。     

退火温度对锗薄膜光学性能和表面结构的影响

研究了退火温度对电子束蒸发制备的锗薄膜光学性能和表面结构的影响规律.在硅基底上制备了厚度约850 nm的Ge薄膜,分别在350、400、450和500℃下进行退火.通过红外光谱仪测试了薄膜的透射率变化,采用光谱反演法得到了薄膜折射率和消光系数的变化规律,使用X射线衍射和原子力显微镜测试了样品的结晶特性和表面形貌.结果 ...     

沉积温度和退火处理对BCN薄膜结构的影响

采用脉冲激光沉积技术,在Si(100)基片上制备了BCN薄膜,研究了沉积温度和退火处理对BCN薄膜组分和结构的影响。利用傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)对制备的BCN薄膜进行了表征。结果表明:沉积温度升高时,BCN薄膜的组分无明显改变。所制备的BCN薄膜包含B—N,C—B和C—N化学键,是由杂化的B—C—N键构成的化合物。真空退火温度为700℃时,BCN薄膜结构稳定;大气退火温度达到600℃时,BCN薄膜表面发生氧化分解,同时有C≡N键形成,表明C≡N键具有较好的高温热稳定性。