残余应力对SrRuO3薄膜磁学及电输运性能的影响

采用射频磁控溅射法在单晶SrTiO₃ (STO)衬底和硅(Si)衬底上制备出不同取向的SrRuO₃ (SRO)薄膜, 对薄膜的残余应力进行了分析, 并研究了应力对不同取向SRO薄膜磁学性能与电输运特性的影响。根据X射线衍射(XRD)结果分析可知, Si基SRO薄膜为多晶单轴取向薄膜, 且应力来源主要为热失配拉应力; STO基SRO薄膜为外延薄膜, 其应力主要为热失配压应力和外延压应力; 磁学性能测试表明, (001)取向SRO薄膜比(110)取向薄膜拥有更高的居里温度T_C; 压应力提高了(001)取向SRO薄膜的T_C, 却降低了(110)取向薄膜的T_C。电阻性能测试表明, 对于在同种类型衬底上沉积的SRO薄膜, (001)取向的薄膜的剩余表面电阻比(RRR)高于(110)取向的薄膜。另外, 拉应力引起了薄膜微结构的无序度增加, 弱化了表面电阻率的温度依赖性, 提高了金属绝缘体转变温度(T_MI)。     

半球谐振子金属化镀膜残余应力的测量方法及影响因素研究

半球谐振子金属化镀膜是半球谐振陀螺制造的重要工艺环节.镀膜过程所产生的薄膜残余应力对谐振子Q值有较大影响,决定着半球谐振陀螺零偏稳定性等最终性能.本文采用X射线衍射法测量薄膜残余应力,研究了镀膜工艺参数和膜层厚度对残余应力的影响,结果表明:薄膜残余应力均呈压应力状态;随着沉积速率的增大,薄膜应力先增大后减小,有转化为拉...     

退火工艺对溶胶凝胶Pb(Zr0.52Ti0.48)O3薄膜残余应力的影响

使用溶胶凝胶法制备了Pb(Zr0.52Ti0.48)O3 铁电薄膜,分别利用原子力显微镜、X射线衍射及面探扫描技术分析了薄膜的组织结构,并运用掠入射X射线衍射法研究了不同工艺条件下制备的薄膜的残余应力.研究表明溶胶凝胶薄膜在600℃退火30min后完全晶化,组织结构均匀.不同工艺下制备的薄膜均受残余拉应力,随着退火温度及退火时间的延长,薄膜中的残余应力逐渐增大,而随着薄膜厚度的增加,残余应力先增大然后减小.     

激光相变硬化残余应力研究

本文主要采用X射线法对激光相变硬化处理后试样表面至内部的残余应力进行逐层测定。并辅以小孔应力释放法予以比较。结果表明:在通常激光相变硬化处理参数下,碳钢的残余应力按正弦波规津分布。表面为压应力,内部为拉应力。其幅值随激光参数减小而减小。二次激光相变硬化处理的残余应力为拉应力。本文对残余应力在激光相变硬化处理热循环过程中的形成进行了解释。在最初升温阶段,表面发生热塑性变形而形成少量压应变。在随后的冷却过程中产生拉应变。当发生奥氏体向马氏体组织转变时,又产生压应变。因此,最终残余应力状态是表面达到的温度,塑性屈服量,组织转变量等因素综合影响的结果。而与是终形成的组织,残余奥氏体量等没有对应关系。     

Pb(Zr,Ti)O3薄膜微区残余应力的X射线面探扫描分析

根据在X射线二维衍射几何关系下建立的应力应变方程,提出了一种基于X射线多晶面探衍射仪系统分析射频磁控溅射制备的Pb(Zr,Ti)O3薄膜微区残余应力的测量方法,即通过基于X射线衍射圆锥形变的分析来表征薄膜的残余应力,试验结果表明薄膜所受为残余拉应力,同时利用X射线面探扫描方法评价了薄膜的残余应力分布.     

喷丸处理对2219铝合金搅拌摩擦焊焊接残余应力的影响

对2219铝合金板进行了搅拌摩擦焊(FSW)和喷丸处理，采用X射线衍射仪(XRD)测量了搅拌摩擦焊和喷丸产生的残余应力，分析了残余应力的分布特征，研究了弹丸直径、弹丸材料、喷射距离等参数对搅拌摩擦焊接残余应力分布的影响。结果表明：焊接后，焊缝附近存在较大的残余拉应力，焊缝中心线±20 mm范围内的平均应力高达100.9 MPa,而远离焊缝的母材区域接近零应力状态；喷丸后，试样残余应力分布发生显著变化，表层残余应力表现为压应力，并且该压应力数值随着深度的增加先增大后减小，最后保持为拉应力；增大弹丸直径可提高最大残余压应力值和残余压应力层深度，但当弹丸直径继续增大至1.2 mm时，最大残余压应力值不再继续增大；选用合适的弹丸材料可获得理想的残余压应力分布情况；随着喷射距离的增大，最大残余压应力值和残余压应力层深度先增大后减小。     

微波辐照对iPP在Al/iPP/Al界面层残余应力的影响

采用薄膜X射线衍射(TF-XRD)方法研究了微波辐照后Al／iPP／Al夹心材料中iPP界面宏观残余应力,微观应力和点阵静畸变应力的变化,结果表明,微波辐照后iPP的宏观残余张应力减小。垂直于[300]晶面(β晶形)的晶粒尺寸增大,β晶形生长趋于完善,晶格微观畸变减小,微观应力减小,α晶形微观应力增大。β晶形的点阵静畸变应力和应力能量小于α晶形,这是引起α→β晶形转变的主要原因。     

用基片曲率法测量薄膜应力

采用基片曲率法设计和制作了一种测量薄膜应力的装置，它具有简单、无损伤、快速、易于操作、精度高的优点。使用该装置测量了射频磁控溅射镀制的Cu单层膜和Ag／Cu多层膜的应力，结果表明薄膜残余应力是均匀的，但随沉积条件不同而不同。Cu单层膜和Ag／Cu多层膜处于压应力状态，外加-200V偏压时，Ag／Cu多层膜则转变为很小的拉应力状态。XRD表明Ag／Cu多层膜已结晶，呈现Ag(111)／Cu(111)择优取向。     

激光相变热处理对TC４电子束焊缝残余应力的影响

利用CO２激光相变热处理技术对TC４钛合金电子束焊缝进行了处理,研究了激光功率、光斑直径、 辅助气体等激光工艺参数对电子束焊缝残余应力分布的影响。实验结果表明,激光相变热处理改善了焊缝残余 应力的分布,使焊缝表面残余应力由拉应力转变为压应力,其压应力值随着激光功率的增加而增大,随着激光 光斑直径的减小而增加;辅助气体为O２时残余压应力值比辅助气体为N２大３０～４０MPa,激光相变热处理显著 提高了TC４钛合金电子束焊缝的残余压应力及其使用寿命。     

干燥过程中小径木表层应力的研究

采用连续加热和间歇加热(间歇2h和间歇6h)方式对小径木锯材进行常规干燥,研究了干燥过程中小径木的表层应力(全应力和残余应力)发生、发展变化规律.结果表明,随着试材的含水率降低,其表层全应力最初表现为拉应力,拉应力增大到最大值后,逐渐减小直至消失,然后转变为压应力,压应力达到最大值后,逐渐减小直到干燥结束;残余应力是先逐渐增大,达到最大后又减小;3种加热方式下,试材表层应力的变化趋势基本一致,但是试材的表层应力间歇加热的明显小于连续加热的,间歇6h试材的表层应力最小;同一含水率水平下,表层应力弦切板的比径切板大.     

Effect of B/C ratio on the physical properties of highly boron-doped diamond films

Highly boron-doped diamond films were deposited on silicon substrate by hot filament chemical vapor deposition in a gas mixture of hydrogen and methane. The chemical bonding states, surface texture, and electrical resistivity of these films were analyzed by X-ray photoelectron spectroscopy, scan electron microscope, and four-point probe method. It was found that boron dopants play an important role in the texture and chemical bonding states of the diamond films. An appropriate concentration of boron dopants (B/C ratio of 10 000 ppm) can simultaneously improve crystal quality and reduce resistivity of the diamond films. The minimum resistivity of diamond films reaches 1.12 × 10⁻² Ω cm, which is applicable as electrodes.     

Stress and phase purity analyses of diamond films deposited through laser-assisted combustion synthesis

Diamond films were deposited on silicon and tungsten carbide substrates in open air through laser-assisted combustion synthesis. Laser-induced resonant excitation of ethylene molecules was achieved in the combustion process to promote diamond growth rate. In addition to microstructure study by scanning electron microscopy, Raman spectroscopy was used to analyze the phase purity and residual stress of the diamond films. High-purity diamond films were obtained through laser-assisted combustion synthesis. The levels of residual stress were in agreement with corresponding thermal expansion coefficients of diamond, silicon, and tungsten carbide. Diamond-film purity increases while residual stress decreases with an increasing film thickness. Diamond films deposited on silicon substrates exhibit higher purity and lower residual stress than those deposited on tungsten carbide substrates.     

Stress and strain in titanium nitride thin films

Titanium nitride (TiN) films, with thickness ranging from 0.02 µm to 1.9 µm, were grown by reactive unbalanced magnetron sputter deposition on silicon substrates. The average film stress is highly compressive in thin films and less compressive in thicker films.Two films, with thicknesses of 0.53 µm and 1.63 µm, were subjected to detailed X-ray diffraction (XRD) analysis. Sin²Ψ analysis was performed, both on films attached to the substrate, as well as on free-standing flakes of the film. The flakes were obtained by dissolving the substrate. Sin²Ψ analysis, both on the films attached to the substrate as well as on the flakes, did not yield straight lines. By combining the sin²Ψ measurements on films attached to the substrate with the sin²Ψ measurements on the flakes we were able to distinguish between a residual deformation of the lattice and the deformation due to the biaxial stress. Following this procedure the stress obtained from wafer curvature and from XRD strain measurements coincides.A residual strain parallel to the growth direction of the crystallites with the <111> direction parallel to the growth direction combined with a changeover in film texture from <001> parallel to growth direction to <111> parallel to growth direction leads us to propose a model explaining the dependence of stress on film thickness in TiN thin films.     

Effects of low temperatures, low pressures and seeding over the crystalline quality, yield and stress of diamond films grown by ECR-assisted chemical vapor deposition

We have studied diamond films grown by electron cyclotron resonance (ECR)-assisted chemical vapor deposition (CVD) on Si (100) substrates seeded with diamond, boron nitride and unseeded. Relatively low temperatures (550–710°C) and low pressures (1–2 Torr) were employed. Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to characterize the crystalline quality, diamond yield, and stresses developed in these films. Most of the diamond films exhibit a Raman blue-shift with respect to natural diamond, indicating that the net stress is compressive. However, this net stress is significantly more compressive than the one estimated by taking into account the thermal interfacial stress and the stress developed at the grain boundaries. In addition, this net stress exhibits an inverse correlation with diamond yield, and a direct correlation with crystalline quality. These results were interpreted in terms of the critical interplay between the supply of precursor species to the growing surface and the surface mobility of adsorbed species. The excess (or intrinsic) compressive stress shows an inverse correlation with diamond crystalline quality, indicating that the creation of point defects serves as a stress-relieving mechanism. Seeding effects, in general, are deleterious to diamond quality, in this temperature and pressure regime studied. Seeding with boron nitride had the effect of reversing the net stress from compressive into tensile, but this effect was rapidly lost as the diamond yield increased.     

硼掺杂对金刚石薄膜生长特性的影响

采用HFCVD方法制备了掺硼金刚石薄膜,通过扫描电子显微镜和X射线衍射光谱对样品的表面形貌及结构进行了分析.结果表明,随着硼含量的增加,薄膜中晶粒的取向由(100)变为(111),然后趋向于无序化.硼的掺入同样影响到孪晶晶粒的形态及生长因子α,使得α变小.通过对样品的Raman光谱分析,得出在适当的硼掺杂浓度下,孪晶的出现使金刚石薄膜中的应力得到松弛,从而中心声子线Raman位移红移较小.     

Effects of doping concentration on the microstructural and optoelectrical properties of boron doped amorphous and nanocrystalline silicon films

Boron doped hydrogenated amorphous silicon thin films were prepared by plasma-enhanced chemical vapor deposition technique at various flow rate of diborane (F_B). As-deposited samples were thermally annealed at the temperature of 800 °C to obtain the doped nanocrystalline silicon (nc-Si) films. The effect of boron concentration on the microstructural, optical and electrical properties of the films was investigated. X-ray photoelectron spectroscopy (XPS) measurements demonstrated the presence of the substitutional boron in the doped films. It was found that thermal annealing can efficiently activate the dopants in films accompanying with formation of nc-Si grains. Based on the temperature-dependent conductivity measurements, it was shown that the dark conductivity of doped amorphous samples increases monotonously with the increase of doping content. While the dark conductivity of doped nc-Si films is not only determined by the concentration of dopant but also the crystallinity of the films. As increasing the flow rate of diborane, the crystallinity of doped nc-Si films decreases, which causes the decrease of dark conductivity. Finally, the high dark conductivity of 178.68 S cm⁻¹ of the B-doped nc-Si thin films can be obtained.     

共掺杂n型CVD金刚石薄膜的结构和性能

利用微波等离子体化学气相沉积(MPCVD)技术制备硫掺杂及硼/硫共掺杂n型金刚石薄膜,探讨n型CVD金刚石薄膜的特性和共掺杂机理.研究结果显示:随着单一硫(S)掺杂含量的增加,金刚石薄膜导电激活能降低,薄膜生长速率减小,薄膜中非金刚石结构相增多;硼/硫(B-S)共掺杂有利于增加硫在金刚石中的固溶度,提高硫在金刚石晶体中的掺杂率,降低金刚石薄膜的导电激活能(在0.26～0.33eV);与单一S掺杂相比较,B-S共掺杂金刚石薄膜生长速率低,薄膜质量和晶格完整性好;霍耳效应测试表明硫掺杂和硼/硫共掺杂金刚石薄膜具有n型导电特征,载流子浓度在1016-1018/cm3之间,载流子迁移率在7～80cm2V-1s-1之间.采用B-S共掺杂技术有利于提高CVD金刚石薄膜的晶格完整性,使得B-S共掺杂金刚石薄膜具有更高的载流子迁移率.     

A positron annihilation study on the defect properties of doped diamond films

Doppler broadening measurements were performed on undoped, boron doped, and sulfur doped diamond films. The defect properties in these different diamond films were analyzed and the effect of boron concentration in the B-doped diamond films on these properties was studied. The Doppler broadening measurements were characterized with the shape parameter S and the wing parameter W. From these fitted characteristic S and W values of the diamond films and plots of S vs. position implantation energy, it was deduced that undoped and S-doped diamond films are rich of vacancy-like defects, while B-doped diamond films are poor of vacancy-like defects. This difference may originate from possible different charge state of the vacancy-like defects and from the incorporation of impurities in the different growth ambient of the films. By comparing the parameters obtained in the Doppler broadening measurements of diamond films with different boron concentration, we found that S values of B-doped diamond did not decreased with the increasing of boron concentration, which suggests that more damaged regions form in the higher boron concentration samples.     

Boron-doped transparent conducting nanodiamond films

Boron-doped nanodiamond (ND) films on silica substrates have been obtained by the method of microwave plasma-enhanced chemical vapor deposition (MWPECVD). Using special technological regimes ensuring the growth of boron-doped ND films after the deposition of an initial ND nucleation layer with small roughness (<15 nm) and a large number of diamond phase nucleation centers per unit surface area (>10¹⁰ cm⁻²), it is possible to obtain conducting ND films transparent in the UV spectral range. Dependence of the transparency and conductivity of the obtained films on the boron concentration and methane content in the working methane-hydrogen mixture has been studied.     

A comparative study of p-type diamond films using Raman and transport measurements

The influence of deposition temperature in the properties of synthetic diamond films grown by two different chemical vapor deposition (CVD) techniques, hot-filament- and microwave-plasma-assisted, was investigated. These samples were obtained using the optimal growth conditions previously achieved in this work. Raman spectroscopy was employed in order to investigate the diamond film quality as a function of the deposition temperature. It was found that the nondiamond carbon bands decrease as the deposition temperature increases for both the deposition methods, leading to higher-quality diamond films. The micro- and macro-Raman spectra showed that the nondiamond band is already present in a single diamond grain. Both techniques provided well homogeneous diamond films and with equivalently good quality. Boron-doped diamond films with different carrier concentration levels were also studied. In order to get details about the electrical properties of the films, resistivity as a function of the boron concentration—in association with Raman spectra—and temperature-dependent transport measurements were employed. The results showed that the boron doping is the main responsible for the conductivity and that the variable range hopping (VRH) mechanism dominates the transport in these doped diamond films.