光学原子力显微镜中的蒙特卡罗方法（英文）

扫描探针显微镜(Scanning probe microscopy, SPM)是显微镜的一个分支,它利用物理探针扫描标本形成样本表面图像。而原子力显微镜(Atomic force microscopy, AFM)是SPM中一种多功能的表面成像和测量工具,对导电、不导电、真空中、空气中或流体中的各种样本均可测量。原子力显微镜最面临的最大挑战之一是评估其在表面测量过程中所伴随的不确定度。本研究通过XYZ Phase的标定,对一台光学原子力显微镜进行了校准。该方法旨在克服在评估一些无法实验确定的不确定部件时遇到的困难,如尖端表面相互作用力和尖端几何。运用蒙特卡罗方法来确定根据相关容差和概率密度函数(PDFs)随机绘制参数而引起的相关不确定度。整个过程遵循《测量不确定度表示指南》(GUM)补编2。经本方法验证,原子力显微镜的评估不确定度为10 nm左右。     

原子力显微镜发展近况及其应用

扫描隧道显微镜(简称STM)和原子力显微镜(简称AFM),它们也可统称为扫描探针显微镜(简称SPM)。原子力显微镜(AFM) 是近十几年来表面成像技术中最重要的进展之一。与扫描电子显微镜相比,它具有较高的分辨率。本文将讨论原子力显微镜的工作原理、原子力显微镜的发展概况和应用。     

用于并行SPM的图像合成技术研究

介绍一种针对并行扫描探针显微镜系统的图像合成算法。利用单探针原子力显微镜(AFM)系统模拟多探针扫描探针显微镜(SPM)并行扫描的图像特征。在图像处理上,将中值滤波器及各种边缘检测算法与成像系统集成在一起,以提高成像质量;同时,依靠原理简单并易于实现的标准化协方差相关法实现相邻探针扫描图像的拼接,采用加权合成算法进行图像的自然融合。实验证明,该算法高效、高精度,合成后的图像与原图相似度达到96%,能够满足并行SPM系统的成像要求。     

MEMS器件圆度误差纳米级测量方法研究

为了测量毫米以下尺寸MEMS零件的圆度参数,建立了将扫描探针显微镜(SPM)系统的原子力测头作为测量传感器,配合精密回转气浮轴系实现对待测试件进行转位的测试系统;讨论了精密气浮轴系、驱动电机、装夹调心装置等关键部件的设计问题及测量系统的工作原理.应用测试系统测量了直径约为0.2mm的微细电极外表面形貌,对获得的表面数据进行了滤波处理,最后使用最小二乘圆度评定准则计算其圆度误差为3.210μm.这种方法可以为圆形MEMS器件的制造工艺提供可行的测量方法与手段.     

原子力显微镜管式扫描器运动学建模与误差分析

针对样本扫描模式原子力显微镜,对其管式扫描器-样本-探针系统进行了运动学分析,建立了该系统的运动学模型,该模型表明:对于给定原子力显微镜扫描器,样本上与探针接触点的横向和纵向位移取决于探针尖端相对于扫描管轴心的偏置量、所加电压(或名义扫描范围)及样本厚度。据此模型,对由于弯曲运动模式所产生的两种重要误差—交叉耦合误差及扫描范围误差进行了定量分析,分析表明:扫描范围误差主要受样本厚度及名义扫描范围影响,而Z向交叉耦合误差主要受探针偏置量及名义扫描范围影响,实验验证了所建立的运动学模型和误差计算公式的正确性;另外,还提出了相应的减小误差的方法。     

在SPM通用平台上自己开发组装扫描探针显微镜

SPM通用平台是一套扫描探针显微镜开发工具系统，它提供了一种开发生产SPM新的思路和方法。使SPM成为通用、开放、兼容的仪器体系。本文介绍了SPM通用平台的原理、指标和在其上扩展扫描隧道显微镜、原子力显微镜等功能模块的方法，以及智能型SPM通用平台的研究思路。希望与相关领域的专家开展合作。     

用于纳米级三维表面形貌及微小尺寸测量的原子力显微镜

SPM是在纳米尺度上进行测量的重要的测量仪器之一,随着SPM进入工业测量领域,SPM的校准、量值溯源和测量不确定度分析已经成为SPM能够作为计量仪器使用的关键所在.文章论述了一种计量型原子力显微镜的构成、校准以及在国际比对中的应用.     

基于相位反馈控制的压电微音叉扫描探针显微镜

压电微音叉具有谐振频率稳定、品质因数高和易于实现音叉臂的振动检测等优点。利用微音叉的这些特性,将其与钨探针结合,构成了压电微音叉扫描探针显微镜(SPM)测头,可实现对微观表面的测量。该测头扫描时,压电微音叉的谐振频率被试样表面原子和钨探针尖端原子间的作用力调制。探针的谐振状态通过锁相环路(PLL)实现,微音叉测头与试样间的恒定测力及测头的Z向定位通过相位反馈控制实现。此外,测量系统可同时获得试样表面的微观轮廓图和相位图。     

基于原子力显微镜的四电极微探针局域电导率测量技术

开发了基于原子力显微镜(Atomic force microscope,ArM)的四电极微探针局域电导率测量技术.四电极AFM探针最小的电极间距为300 nm,安装了这种新型四电极微探针的AFM系统既保持表面微观形貌测量能力,又可以在实施表面形貌扫描的同时测定局域电导率.利用该技术精确测量了厚度为6.0μm的铝薄膜和厚度为350nm的透明导电氧化铟薄膜(Indiumtin oxide,ITO)的局域电导率,试验结果证明基于AFM的四电极微探针技术在亚微米局域电导率测量方面的能力.     

复合型超精密表面形貌测量仪

研制了基于同一显微镜基体实现原子力探针扫描测量与非接触光学测量两种功能的复合型超精密表面形貌测量仪.分析了基于白光显微干涉原子力探针的测量方法、探针微悬臂变形量与白光干涉条纹移动量的关系以及探针微悬臂测量非线性误差的修正方法,和通过融合垂直扫描系统的位移量和悬臂梁变形量得到了原子力探针的工作方式.研制了三维精密位移系统...     

Direct deformation study of AFM probe tips modified by hydrophobic alkylsilane self-assembled monolayers

The in-use wear of atomic force microscopy (AFM) probe tips is crucial for the reliability of AFM measurements. Increase of tip size for several nanometers is difficult to monitor but it can already taint subsequent AFM data. We have developed a method to study the shape evolution of AFM probe tips in nanometer scale. This approach provides direct comparison of probe shape profiles, and thus can help in evaluation of the level of tip damage and quality of acquired AFM data. Consequently, the shape degradation of probes modified by hydrophobic alkylsilane self-assembled monolayers (SAMs) was studied. The tip wear length and wear volume were adopted to quantitatively verify the effectiveness of hydrophobic coatings. When compared with their silicon counterparts, probes modified by SAM materials exhibit superior wear-resistant behavior in tapping mode scans.     

Simulation-aided design and fabrication of nanoprobes for scanning probe microscopy

We proposed and demonstrated a flexible and effective method to design and fabricate scanning probes for atomic force microscopy applications. Computer simulations were adopted to evaluate design specifications and desired performance of atomic force microscope (AFM) probes; the fabrication processes were guided by feedback from simulation results. Through design-simulation-fabrication iterations, tipless cantilevers and tapping mode probes were successfully made with errors as low as 2% in designed resonant frequencies. For tapping mode probes, the probe tip apex achieved a 10 nm radius of curvature without additional sharpening steps; tilt-compensated probes were also fabricated for better scanning performance. This method provides AFM users improved probe quality and practical guidelines for customized probes, which can support the development of novel scanning probe microscopy (SPM) applications.     

Design and performance of a combined secondary ion mass spectrometry-scanning probe microscopy instrument for high sensitivity and high-resolution elemental three-dimensional analysis

State-of-the-art secondary ion mass spectrometry (SIMS) instruments allow producing 3D chemical mappings with excellent sensitivity and spatial resolution. Several important artifacts however arise from the fact that SIMS 3D mapping does not take into account the surface topography of the sample. In order to correct these artifacts, we have integrated a specially developed scanning probe microscopy (SPM) system into a commercial Cameca NanoSIMS 50 instrument. This new SPM module, which was designed as a DN200CF flange-mounted bolt-on accessory, includes a new high-precision sample stage, a scanner with a range of 100 μm in x and y direction, and a dedicated SPM head which can be operated in the atomic force microscopy (AFM) and Kelvin probe force microscopy modes. Topographical information gained from AFM measurements taken before, during, and after SIMS analysis as well as the SIMS data are automatically compiled into an accurate 3D reconstruction using the software program "SARINA," which was developed for this first combined SIMS-SPM instrument. The achievable lateral resolutions are 6 nm in the SPM mode and 45 nm in the SIMS mode. Elemental 3D images obtained with our integrated SIMS-SPM instrument on Al/Cu and polystyrene/poly(methyl methacrylate) samples demonstrate the advantages of the combined SIMS-SPM approach.     

Atomic and magnetic force microscopy imaging of thin-film recording heads

Investigations on the use of the scanning probe microscope (SPM) in the atomic force microscopy (AFM) mode for topography imaging and the magnetic force microscopy (MFM) mode for magnetic imaging are presented for a thin-film recording head. Results showed that the SPM is suitable for imaging the surface profile of the recording head, determining the width of the pole gap region, and mapping the magnetic field patterns of the recording head excited under current bias conditions of different polarity. For the cobalt sputter-coated tips used in MFM imaging, it was found that the magnetic field patterns obtained under different polarities of the current bias to the recording head were similar. This can be explained by the nature of the thin-film MFM tip, in which the direction of the tip magnetic moment can follow the stray magnetic field of the sample as the current bias to the recording head reverses in direction.     

Blind estimation of general tip shape in AFM imaging

The use of flared tip and bi-directional servo control in some recent atomic force microscopes (AFM) has made it possible for these advanced AFMs to image structures of general shapes with undercut surfaces. AFM images are distorted representations of sample surfaces due to the dilation produced by the finite size of the tip. It is necessary to obtain the tip shape in order to correct such tip distortion. This paper presents a noise-tolerant approach that can for the first time estimate a general 3-dimensional (3D) tip shape from its scanned image in such AFMs. It extends an existing blind tip estimation method. With the samples, images, and tips described by dexels, a representation that can describe general 3D shapes, the new approach can estimate general tip shapes, including reentrant features such as undercut lines.     

Traceable atomic force microscope based on monochromatic light interference

Atomic force microscope (AFM) is widely applied to the measurement of the micro-nano structures due to its three-dimensional spatial resolution of sub-nanometer. However, the height measurement traceability in the z-axis is complex to be implemented in conventional AFMs. In this paper, a traceable AFM is developed based on the monochromatic light interference (MLI) principle without probe calibration. The height change of the AFM's probe is directly detected by extracting the phase change of the MLI fringes on the probe tip with the Hilbert transform based phase extraction algorithm, and the three-dimensional surface topography is reconstructed with a surface recovery algorithm. The configuration of tracing to the wavelength of the monochromatic light in real-time further improves the measurement accuracy of the MLI-AFM. A prototype MLI-AFM is established to demonstrate its measurement accuracy enhancement.     

Imaging tip formation in single-mode optical fibres

The formation of probe tips is a crucial step in all forms of scanning probe microscopy (SPM). In this work single-mode optical fibres are chemically etched in a variable temperature bath of etchant solution (HF acid buffered with ammonium fluoride) to produce tips for optical SPM. Tip evolution is monitored by prematurely truncating the etching process and imaging the tip end-structure using atomic force microscopy (AFM). In the case of a visible regime single-mode fibre the AFM images show a remarkable ring structure in the central cladding region and a tip structure in the core with a central depression; this serves to demonstrate the efficacy of chemical etching for converting compositional variation to three-dimensional topography. In the case of a standard, single-mode optical communications fibre the (projected) tip cone angle is assessed from AFM images in the early stages of tip formation. Values of the cone angle thus determined, for different etch conditions, are compared to those predicted by a model in which the independently determined core and cladding etch rates, and core diameter are the sole determinants of the final tip geometry. The model was devised in the context of etching multi-mode fibres and is shown to be valid here for single-mode fibres within the range of experimental accuracy and etch conditions examined.     

In-plane contributions to phase contrast in intermittent contact atomic force microscopy

Contrast in the phase response of intermittent-contact atomic force microscopy (IC-AFM) reveals in-plane structural and mechanical properties of polymer monolayers. This result is unexpected, as IC-AFM has previously only been considered as a probe of out-of-plane properties. Until now, AFM measurements of nanoscale in-plane properties have employed contact mode techniques. In-plane property measurements are possible with intermittent contact AFM because there is a small but significant component of tip motion parallel to the sample surface. This in-plane component of tip displacement is virtually universal in AFM, implying that oscillating-tip techniques generally are sensitive to in-plane material properties. We present a simple Hertzian model of intermittent-contact AFM that includes such an in-plane displacement.     

Computational models of a nano probe tip for static behaviors

It is difficult to predict the measurement bias arising from the compliance of the atomic force microscope (AFM) probe. The issue becomes particularly important in this situation where nanometer uncertainties are sought for measurements with dimensional probes composed of flexible carbon nanotubes mounted on AFM cantilevers. We have developed a finite element model for simulating the mechanical behavior of AFM cantilevers with carbon nanotubes attached. Spring constants of both the nanotube and cantilever in two directions are calculated using the finite element method with known Young's moduli of both silicon and multiwall nanotube as input data. Compliance of the nanotube-attached AFM probe tip may be calculated from the set of spring constants. This paper presents static models that together provide a basis to estimate uncertainties in linewidth measurement using nanotubes. In particular, the interaction between a multiwall nanotube tip and a silicon sample is modeled using the Lennard-Jones theory. Snap-in and snap-out of the probe tip in a scanning mode are calculated by integrating the compliance of the probe and the sample-tip interacting force model. Cantilever and probe tip deflections and points of contact are derived for both horizontal scanning of a plateau and vertically scanning of a wall. The finite element method and the Lennard-Jones model provide a means to analyze the interaction of the probe and sample and measurement uncertainty, including actual deflection and the gap between the probe tip and the measured sample surface.     

Atomic force microscope imaging and force measurements at electrified and actively corroding interfaces: challenges and novel cell design

We report the design of an improved electrochemical cell for atomic force microscope measurements in corrosive electrochemical environments. Our design improvements are guided by experimental requirements for studying corrosive reactions such as selective dissolution, dealloying, pitting corrosion, and∕or surface and interface forces at electrified interfaces. Our aim is to examine some of the limitations of typical electrochemical scanning probe microscopy (SPM) experiments and in particular to outline precautions and cell-design elements, which must necessarily be taken into account in order to obtain reliable experimental results. In particular, we discuss electrochemical requirements for typical electrochemical SPM experiments and introduce novel design features to avoid common issues such as crevice formations; we discuss the choice of electrodes and contaminations from ions of reference electrodes. We optimize the cell geometry and introduce standard samples for electrochemical AFM experiments. We have tested the novel design by performing force-distance spectroscopy as a function of the applied electrochemical potential between a bare gold electrode surface and a SAM-coated AFM tip. Topography imaging was tested by studying the well-known dealloying process of a Cu(3)Au(111) surface up to the critical potential. Our design improvements should be equally applicable to in situ electrochemical scanning tunneling microscope cells.