考虑摩擦力及试样表面倾角的原子力显微镜扫描模式

原子力显微镜(Atomic force microscopes,AFM)接触模式下的测量结果因受样本表面倾角和针尖一样本表面间摩擦力的影响而存在较大的测量误差.为避免针尖-表面间的摩擦力对AFM测量试样表面形貌的影响,并能够准确测量表面倾角,提出了一种新的AFM工作模式--消除倾角和摩擦力影响模式.在这种工作模式中,扫描方向垂直悬臂的长轴方向,通过测量悬臂的竖向和横向偏转而得到针尖所受的竖向和横向力,并计算得到针尖-试样表面间的van der Waals力及试样表面局部倾角,然后结合针尖项点和扫描器的位置及针尖-试样表面间距可以得到试样表面形貌的测量结果.在上述工作模式下,针尖-试样表面间的摩擦力是可控的,能够避免针尖或试样的损伤.仿真结果证明了这种方法的可行性.     

类金刚石薄膜纳米摩擦性能的试验研究

利用摩擦力显微镜(FFM),对由等离子体增强化学气相法沉积的类金刚石(DLC)薄膜的纳米摩擦性能进行了试验研究。用原子力显微镜(AFM)观察了DLC薄膜样品的表面形貌,同时测定了其粘附力值。从外加载荷、扫描速度和湿度的角度分析了薄膜的摩擦特性。     

分子沉积(MD)膜表面形貌的测量及影响因素

利用原子力显微镜 (AFM)考察了单层磺化酞菁铜 (CuTsPc)MD膜硅表面随载荷和扫描速率变化的盒维数 ,对单层CuTsPcMD膜硅表面进行了表面形貌的测量 ,并分析了形貌信息中的摩擦力信息对表面形貌信号的影响。结果表明 ,单层CuTsPcMD膜硅表面具有较好的分形几何特性 ,分形是表面的固有属性 ;不同类型的硅表面具有的盒维数基本不变。表面形貌的信息里包含的摩擦力信息是表面形貌测量中的重要影响因素 ,载荷和扫描速率通过影响摩擦力对表面形貌的测量产生影响 ,但载荷影响程度不大 ,且没有较明显的规律 ;扫描速率增加能引起表面粗糙度和表面高度的降低。     

典型构筑植物表面不同湿度条件下黏附和摩擦特性研究

利用原子力显微镜的胶体探针技术,对不同湿度条件下四种具有典型构筑（光滑二维蜡质层、微褶皱、大褶皱、三维蜡质晶体）的原始植物表面以及两种氯仿处理后的植物样品表面的黏附力和摩擦力进行定量测试和分析。试验结果表明：冬青叶表面光滑二维蜡质涂层降低了其表面能和亲水特性,这不仅降低胶体探针与其表面在干燥条件下固固接触的摩擦力和黏附力,而且有效地阻碍了小湿度条件下液桥的形成,提高了其在小湿度条件下的脱附性能;荔枝叶表面微褶皱结构特征增大了固固接触的缝隙,不利于空气中的水蒸气冷凝并在毛细力的作用下形成液桥,从而在更大的湿度范围内提高了其脱附能力,脱附效果优于二维蜡质涂层;仙客来表面大褶皱特征和猪笼草表面三维蜡质晶体能有效排除接触界面附近的水蒸气,在干燥条件和高湿度条件下均能保持高效脱附功能,而猪笼草表面的微结构特征和蜡质晶体低表面能的耦合作用使其具有比仙客来表面大褶皱结构特征更优良的脱附功能。这些研究成果为仿生反黏附表面的设计和制备提供了理论依据。     

红细胞表面摩擦特性的AFM研究

利用CSPM5000型原子力显微镜观察了吸附在云母基底上的红细胞表面形貌,对比分析了云母表面和红细胞表面微摩擦力回路曲线及摩擦力-载荷关系曲线,通过观察红细胞表面形貌及对其表面进行摩擦力分析发现:由于红细胞表面柔软粗糙,且其表面吸附一定的血浆和水,导致测得微观摩擦力较大;红细胞表面的摩擦力随载荷的增大而增大;坚硬的探针与柔软的红细胞表面接触并施加一定的载荷时,载荷增大首先使红细胞发生变形,当载荷增大到红细胞膜的变形极限时会导致红细胞膜破损,此时所测得的摩擦力为探针切割红细胞膜的力.     

类金刚石薄膜微观摩擦性能的FFM评价——针尖尺度效应

采用等离子体增强气相沉积制备了类金刚石薄膜，利用原子力显微镜的轻敲模式观察了它们的形貌，并在考虑外加载荷和扫描速度的基础上，用摩擦力显微镜（FFM）对比考察了尖端探针和平头探针对类金刚石薄膜摩擦性能评价的影响。结果表明：类金刚石薄膜的表面粗糙度随基底负偏压的增加而减小；存在于探针和类金刚石薄膜之间的水膜对尖端探针的剪切阻力贡献较大，且尖端探针测得的摩擦力变化趋势受扫描速度影响显著；水膜对平头探针起着不同形式的润滑作用，从而导致平头探针和类金刚石薄膜之间摩擦性能的速度效应存在差异；利用摩擦力显微镜考察类金刚石薄膜的摩擦性能时，存在着明显的针尖尺寸效应。     

人脐静脉内皮细胞形貌与表面粘附力的原子力显微镜表征

目的:探讨原子力显微镜(AFM)在研究人脐静脉内皮细胞(ECV304)表面形貌、超微结构及纳米机械性质等方面的应用,讨论ECV304超微结构和机械性质与其功能的关系。方法:利用AFM对ECV304细胞的表面形貌及生物机械性质进行表征与测量。结果:在AFM下观察到用普通光学显微镜难以观察到的ECV304细胞的独特的形态结构,如细胞骨架、伪足及细胞边缘微丝等。ECV304细胞呈现长梭形、多角形、圆形等多种形态,细胞表面平均粗糙度为320.52±75.98 nm,表面均匀分布微绒毛,细胞周围有铺展的圆盘状物质。力曲线定量分析得出针尖与细胞表面的非特异性粘附力为75±14 pN。结论:通过AFM成像和力曲线测量表明,ECV304细胞呈圆形,多角形,梭形等多种形态,针尖与细胞膜表面问的粘附力比较小,约75±14pN。     

钛合金表面红细胞吸附特性AFM研究

采用原子力显微镜(AFM)观察吸附在钛合金基底上的红细胞表面形貌,研究红细胞、钛合金与探针之间的微摩擦力,对比分析红细胞表面和钛合金表面同探针之间的微摩擦力-距离关系曲线,及红细胞破损前后的探针与红细胞的微摩擦力-距离关系曲线。结果表明:在外力作用下,红细胞不仅细胞表面形貌受影响,而且其黏性增大,摩擦力增大,影响润滑效果;因红细胞表面柔润粗糙,且探针在活细胞表面所测得的微摩擦力为多种微观力的合力,从而使红细胞表面的摩擦力较大。     

基于精确探针模型的AFM图像重构研究

原子力显微镜技术已在纳米成像中得到了普遍应用.但实验表明,AFM图像在水平方向分辨率较低,其中探针针尖形貌是影响扫描图像分辨率的关键因素之一.为了提高AFM扫描图像的分辨率,改善成像质量,一种可行的方法是通过建立探针模型后,重构扫描图像.在已有的探针建模方法中,普遍采用盲建模算法.针对目前盲建模算法中降噪阈值难以优化问题,提出了一种降噪阈值最优估计新方法.该方法可以使盲建模算法更准确地建立扫描方向上的探针形貌轮廓,进而完成3D探针模型.通过应用AFM探针扫描多空铝和标准栅格实验,介绍了探针针尖形貌精确建模的方法.然后使用数学形态学的腐蚀运算对标准栅格的AFM成像进行了重构,验证了上述方法的有效性.实验结果证明,重构后的图像中降低了探针针尖形貌的失真影响,可以显著改善扫描探针显微镜成像的水平分辨率.     

基于数学形态学方法的AFM探针建模研究

AFM扫描图像可被认为是探针针尖的形貌和扫描样品表面形貌的数学形态学卷积结果,需要用反卷积的方法排除扫描图像中探针形貌引起的失真影响。本文在已有基于数学形态学的探针盲建模算法基础上,提出了一种可快速实现特征点优化提取的方法,同时提出了一种可降低最优降噪阈值估计复杂性的基于临界阈值搜索新方法。最后给出了仿真与CNT扫描图像的重构实验结果。实验表明,本文介绍的方法提高了探针建模的计算速度和建模精度,可以对AFM成像质量进行有效的失真修正和改善。     

Surface characterization and adhesion and friction properties of hydrophobic leaf surfaces

Super-hydrophobic surfaces as well as low adhesion and friction are desirable for various industrial applications. Certain plant leaves are known to be hydrophobic in nature. These leaves are hydrophobic due to the presence of microbumps and a thin wax film on the surface of the leaf. The purpose of this study is to fully characterize the leaf surface and to separate out the effects of the microbumps and the wax on the hydrophobicity. Furthermore, the adhesion and friction properties of the leaves, with and without wax, are studied. Using an optical profiler and an atomic/friction force microscope (AFM/FFM), measurements on the hydrophobic leaves, both with and without wax, were made to fully characterize the leaf surface. Using a model that predicts contact angle as a function of roughness, the roughness factor for the hydrophobic leaves has been calculated, which is used to calculate the contact angle for a flat leaf surface. It is shown that both the microbumps and the wax play an equally important role in the hydrophobic nature as well as adhesion and friction of the leaf. This study will be useful in developing super-hydrophobic surfaces.     

Investigating ultra-thin lubricant layers using resonant friction force microscopy

The ultrasonic friction mode of an atomic force microscope is a scanning probe technique allowing one to analyze the load and velocity dependence of friction. The technique is based on evaluation of the resonance behavior of an AFM cantilever when in contact with a vibrating sample surface. The effect of load and lateral displacement of the sample surface on the shape of the torsional resonance spectra of the AFM cantilever is evaluated under dry and lubricated sliding conditions. A characteristic flattening of the torsional resonance curve has been observed at large surface displacements, resulting from the onset of sliding friction in the AFM cantilever–sample surface contact. An analytical model describing torsional cantilever vibrations in Hertzian contact with a sample surface is presented, and numerical simulations have been carried out in order to confirm that the flattening of the resonance curve occurs with the onset of the sliding friction in the contact.     

Adhesion and Friction Studies of Nano-textured Surfaces Produced by Self-Assembling Au Nanoparticles on Silicon Wafers

This article presents the results of nanoscale friction and adhesion of nanoparticle-textured surfaces (NPTS) using atomic force microscope (AFM). The effects of coverage ratio, texture height, and packing density on the adhesion and friction of the NPTS were investigated. The nano-textured surfaces were produced by self-assembling Au nanoparticles (NPs) with diameters of 20 nm and 50 nm on the silicon (100) surfaces, respectively. Surface morphology of the NPTS was characterized by field emission scanning electron microscopy and AFM. The results show that the NPTS significantly reduced the adhesive force compared to the smooth surface. The adhesion of NPTS is mainly dependent on the coverage ratio of NPs rather than the texture height and higher coverage ratio resulted in smaller adhesive force. The reduced adhesion of textured surfaces was attributed to the reduced real area of contact. The friction of NPTS is mainly dependent on the spacing between asperities. The lowered frictional force was obtained when the spacing between asperities is less than the size of AFM tip, because of the effectively reduced real area of contact between the AFM tip and the NPTS surface.     

Friction Force of Locust <Emphasis Type="Italic">Locusta migratoria manilensis</Emphasis> (Orthoptera,Locustidae) on Slippery Zones of Pitchers from Four <Emphasis Type="Italic">Nepenthes</Emphasis> Species

Slippery zone of inner pitchers in Nepenthes species serves functions of trapping insect and restraining escape of prey being used as a main nitrogen and phosphorus source. To investigate the influence of the slippery zones from different Nepenthes species on friction force of insect possessing smooth adhesive pads and rigid claws, friction force of locust Locusta migratoria manilensis on slippery surface of pitchers from four Nepenthes species was measured. The friction force of locust was also measured on stainless steel plate for comparison. Different friction forces were showed among the four Nepenthes species (mainly 380–550 mN in imagines, 120–185 mN in larvae), and were apparently lower than on the stainless steel plates (mainly 650 mN in imagines, 230 mN in larvae). Surface morphologies and structures of the slippery zones were observed and analyzed with scanning electron microscope and scanning white-light interferometer to explain the discrimination of the friction force. The slippery zones from the selected Nepenthes species exhibited similar surface morphologies and structures, but differed obviously in the geometrical dimensions of the surface architectures, and the difference probably result in the discriminations of the locust’s friction force. The obtained results contribute to further interpretation of the slippery zone’s anti-attachment mechanism to insect and presumably supply suitable theoretical foundations for biomimeticing structure and function of the slippery zone to develop slippery plates for trapping plague locusts or other agricultural pests.     

阴离子表面活性剂及复配对阻挡层抛光液性能的影响

为提高铜互连化学机械抛光(CMP)后表面质量，在抛光液中需引入适当的表面活性剂以改善磨料的稳定性以及CMP后铜的表面粗糙度。研究了十二烷基硫酸铵(ADSA)、脂肪醇聚氧乙烯醚硫酸铵(AESA)、直链烷基苯磺酸(LABSA)3种不同阴离子表面活性剂，以及非离子表面活性剂脂肪醇聚氧乙烯醚(AEO-9)和LABSA复配表面活性剂对钽阻挡层抛光液润湿性、分散性以及对材料去除速率的影响。通过接触角测量仪、纳米粒度仪、扫描电镜和原子力显微镜测试表面张力、接触角、大颗粒数、粒径分布以及CMP后铜的表面粗糙度，并分析复配表面活性剂的作用机制。结果表明：抛光液中加入LABSA后，因其具有直链型结构，抛光液的润湿性和分散性效果最好，抛光后铜表面的粗糙度最低；AEO-9和LABSA进行复配，相较于单一的LABSA,抛光液的润湿性、分散性、稳定性和抛光后铜表面粗糙度均有所改善，体积分数0.1%LABSA+0.1%AEO-9的复配表面活性剂性能最优，CMP后铜表面粗糙度降至0.7 nm。     

Atomic force microscopy characterization of the chemical contrast of nanoscale patterns fabricated by electron beam lithography on polyethylene glycol oxide thin films

The present paper shows that atomic force microscopy (AFM) imaging of friction force and phase lag in ambient air can be used to characterize the chemical contrast induced by electron beam (EB) irradiation on polyethylene glycol oxide (PEO) surface. Time-of-flight secondary emission mass spectroscopy measurements showed that the EB irradiation generates chemical contrast on PEO surface by decreasing the ether bond density. The AFM measurements showed smaller phase lag and lower friction and adhesive forces on the EB irradiated PEO surface, as compared to the non-irradiated PEO surface. While the chemical contrast in friction force had a linear dependence on the EB irradiation dose, the dependence of the chemical contrast in the phase lag was strongly non-linear. As the friction and adhesive forces depended on the AFM probe hydrophilicity and air humidity, the contrast in friction and adhesive forces is ascribed to different capillary condensation of ambient water vapour at the AFM tip contact with the EB irradiated and non-irradiated PEO surfaces, respectively.     

Demonstration of topography modification by friction processes and vice versa

Contact formation and development are the basis of friction and wear modelling and understanding. Unanimously topography formation and development in friction contacts are regarded of highest importance for understanding and modelling friction processes. The frequently found running in behaviour of sliding contacts is—aside from the build up of reaction and transfer layers-at least partly caused by the topography development due to friction processes until a stable equilibrium state is reached.Experimental results of friction and topography measurements are presented which demonstrate the mutual modification of friction and contact topography.A special experimental set up with an AFM allowed to correlate the measured friction forces with the contact position and the topography at this point. In this way, friction force transitions and changes can be assigned to topography changes due to abrasion, adhesion and wear particle agglomeration.Contact surfaces with artificial regular structures have been prepared to avoid problems with topography and friction correlation due to the statistical nature of roughness on technical contact surfaces. The friction effects of roughness were simulated by etched ditches of defined width, depth and distance on silicon or metal surfaces. This allowed to explain the mutual influences of topography and friction. The effect of a single ‘asperity’ and of the ‘roughness structures’ could be demonstrated.Topography measurements with an AFM correlated with the friction force could help to understand friction changes without changing any parameter.     

基于DMT模型的金刚石表面纳米摩擦学研究

基于DMT接触模型，在理论上计算金刚石表面纳米摩擦的摩擦力和摩擦因数；采用原子力显微镜，以金刚石探针和片状金刚石试件作为摩擦副，在大气环境下分别研究机械抛光和聚焦离子束（FIB）刻蚀的金刚石试件的摩擦学特性，并比较实验结果和DMT接触模型计算结果。结果表明：金刚石试件的摩擦因数均随着载荷的增加而减小，这与以往对金刚石微观摩擦的研究结果相符合；DMT接触模型计算结果与机械抛光表面试验结果吻合较好，而略高于FIB刻蚀表面试验结果，验证了DMT模型在金刚石纳米摩擦研究中的适用性。通过表面粗糙度和碳原子化学状态分析，得出粗糙表面对探针滑动的阻碍作用和FIB刻蚀过程中生产的非晶碳的减摩作用是DMT模型应用于上述2种加工表面产生差异的原因。     

模块化扫描探针显微镜的研究

介绍一种多功能、模块化扫描探针显微镜,它综合了ＳＴＭ、ＡＦＭ、ＭＦＭ、ＦＦＭ等的功能,不仅能检测物质表面微观形貌,还能检测微小静电力、磁力、原子力和摩擦力,具有较好的灵活性和较宽的应用范围。