一种新颖的点衍射干涉轻敲模式原子力显微镜

论述了一种新颖的原子力显微镜,它利用硅微探针的特殊结构和相关光学系统所引起的点衍射干涉现象[1]来扫描成像,因为硅微探针被用作反射型点衍射板,故光路完全共路,再结合锁相检测技术,使得该仪器抗干扰力极强且结构精巧紧凑,可适用于测试软硬不同材料样品,对软质高分子膜材料检测得到了实际的链状结构。     

Analysis of dynamic cantilever behavior in tapping mode atomic force microscopy

Tapping mode atomic force microscopy (AFM) provides phase images in addition to height and amplitude images. Although the behavior of tapping mode AFM has been investigated using mathematical modeling, comprehensive understanding of the behavior of tapping mode AFM still poses a significant challenge to the AFM community, involving issues such as the correct interpretation of the phase images. In this paper, the cantilever's dynamic behavior in tapping mode AFM is studied through a three dimensional finite element method. The cantilever's dynamic displacement responses are firstly obtained via simulation under different tip‐sample separations, and for different tip‐sample interaction forces, such as elastic force, adhesion force, viscosity force, and the van der Waals force, which correspond to the cantilever's action upon various different representative computer‐generated test samples. Simulated results show that the dynamic cantilever displacement response can be divided into three zones: a free vibration zone, a transition zone, and a contact vibration zone. Phase trajectory, phase shift, transition time, pseudo stable amplitude, and frequency changes are then analyzed from the dynamic displacement responses that are obtained. Finally, experiments are carried out on a real AFM system to support the findings of the simulations. Microsc. Res. Tech. 78:935–946, 2015. © 2015 Wiley Periodicals, Inc.     

大范围扫描原子力显微镜自动调平控制技术

为了进一步扩大原子力显微镜(AFM)的应用范围,研制出一套大范围高速AFM系统.该系统采用上、下两个扫描器,上扫描器负责Z方向闭环控制的动态响应,下扫描器负责X、Y方向平面扫描及Z方向补偿控制.针对样品放置倾斜对大范围扫描成像的影响,提出基于多线扫描的样品自动调平控制技术.首先通过多线扫描确定样品倾斜位置,然后将所有扫描点的倾斜位移差用函数式表达,最后将位移差换算为控制电压作为扫描器Z向的前馈控制输入.实验结果表明,能消除样品倾斜对AFM大范围扫描的影响.     

A convenient and rapid sample repositioning approach for atomic force microscopy

A novel repositioning approach is described for repeated observations of a specimen at a close proximal location in the atomic force microscope. The approach is similar to keystone architecture, whereby the repositioning is achieved by forming a male structured base for the specimen, and a corresponding female counterpart as the frame. For the combination of an acrylic acid frame and a metal base, 90% translation shifts are less than 10 µm, and almost all angular disorientations are within +3° to ?3°. Nanometre‐scale surface features can be relocated easily and reliably even after 40 imaging–removal–imaging cycles, dipping the specimen in solutions or heating up to 500 °C.     

Optimizing AC-mode atomic force microscope imaging

We have operated an atomic force microscope in ambient air with several oscillating cantilever modes to establish the optimal scanning parameters to maximize image resolution and to minimize probe and sample damage. This was done by scanning a surface in air and correlating scan parameters such as oscillation amplitude and damping with image resolution. We also examined the geometry of the probe with a scanning electron microscope, before and after scanning, in order to determine whether the scanning technique had an effect on the geometry of the probe tip. If the probe is oscillated such that it contacts the surface on each oscillation, substantial damage or “wear” to the probe occurs and significant degradation of image quality was observed. In ambient air, the optimal conditions are achieved when the probe penetrates the contamination layer and reverses direction before touching the surface. Under these “near-contact” conditions no probe damage is observed and high-image resolution can be maintained indefinitely.     

Dynamic analysis of tapping mode atomic force microscope (AFM) for critical dimension measurement

Transient dynamics of tapping mode atomic force microscope (AFM) for critical dimension measurement are analyzed. A simplified nonlinear model of AFM is presented to describe the forced vibration of the micro cantilever-tip system with consideration of both contact and non-contact transient behavior for critical dimension measurement. The governing motion equations of the AFM cantilever system are derived from the developed model. Based on the established dynamic model, motion state of the AFM cantilever system is calculated utilizing the method of averaging with the form of slow flow equations. Further analytical solutions are obtained to reveal the effects of critical parameters on the system dynamic performance. In addition, features of dynamic response of tapping mode AFM in critical dimension measurement are studied, where the effects of equivalent contact stiffness, quality factor and resonance frequency of cantilever on the system dynamic behavior are investigated. Contact behavior between the tip and sample is also analyzed and the frequency drift in contact phase is further explored. Influence of the interaction between the tip and sample on the subsequent non-contact phase is studied with regard to different parameters. The dependence of the minimum amplitude of tip displacement and maximum phase difference on the equivalent contact stiffness, quality factor and resonance frequency are investigated. This study brings further insights into the dynamic characteristics of tapping mode AFM for critical dimension measurement, and thus provides guidelines for the high fidelity tapping mode AFM scanning.     

Improving tapping mode atomic force microscopy with piezoelectric cantilevers

This article summarizes improvements to the speed, simplicity and versatility of tapping mode atomic force microscopy (AFM). Improvements are enabled by a piezoelectric microcantilever with a sharp silicon tip and a thin, low-stress zinc oxide (ZnO) film to both actuate and sense deflection. First, we demonstrate self-sensing tapping mode without laser detection. Similar previous work has been limited by unoptimized probe tips, cantilever thicknesses, and stress in the piezoelectric films. Tests indicate self-sensing amplitude resolution is as good or better than optical detection, with double the sensitivity, using the same type of cantilever. Second, we demonstrate self-oscillating tapping mode AFM. The cantilever's integrated piezoelectric film serves as the frequency-determining component of an oscillator circuit. The circuit oscillates the cantilever near its resonant frequency by applying positive feedback to the film. We present images and force-distance curves using both self-sensing and self-oscillating techniques. Finally, high-speed tapping mode imaging in liquid, where electric components of the cantilever require insulation, is demonstrated. Three cantilever coating schemes are tested. The insulated microactuator is used to simultaneously vibrate and actuate the cantilever over topographical features. Preliminary images in water and saline are presented, including one taken at 75.5 μm/s—a threefold improvement in bandwidth versus conventional piezotube actuators.     

基于平板扫描器的新型AFM系统

研制了一种基于平板扫描器的新型原子力显微镜(AFM)系统。该系统创新地把二维平板扫描器和一维反馈控制器相结合,有效地克服了传统扫描器Z向反馈控制与XY扫描平面之间的非线性交叉耦合误差,同时保证了大范围扫描时检测光路的稳定性。利用该系统与传统AFM作了氧化铝薄膜和光栅对比扫描实验,结果表明这种AFM系统能够获得无扭曲、规则的理想图像。     

原子力显微镜的力曲线分析与转化

原子力显微镜测定的力曲线需转化为力位移曲线来应用.力位移曲线是以任意点为零点的,当研究粘附或者分子模型对比时,需要知道针尖样品间的作用力或确切的零点位置,这时需将其转化为力-距离曲线.本文首先从力曲线的测定原理得出了典型的力曲线,之后从理论上分析了力曲线、力位移曲线和力-距离曲线间的转化,从中得出了转化过程中需要的两个重要参量:灵敏度和零距离,并提出了确定方法.最后,利用MATLAB实现了曲线的自动转化.     

Recent advances in atomic force microscopy of DNA

Three advances involving DNA in atomic force microscopy (AFM) are reported here. First a HEPES-Mg buffer has been used that improves the spreading of DNA and provides good DNA coverage with as little as 200–500 picograms per sample. Second, the new “tapping” mode has been used to improve the ease and resolution of AFM-imaging of DNA in air. Finally, AFM images are presented of single-stranded ΦX-174 virion DNA with the gene 32 single-stranded binding protein. A summary of the current state of the field and of the methods for preparing and imaging DNA in the AFM is also presented.     

原子力显微镜(AFM)在光盘检测及其质量控制中的应用

综述了原子力显微镜(AFM)在光盘质量检测中的应用.AFM能够在nm尺度上直接对光盘及其模板上的信息位几何结构的特征尺寸及其误差进行三维测量,从而可以建立生产工艺参数和信息位几何结构之间、信息位几何结构和盘片电气性能之间的关系,进而找出影响光盘质量的直接原因.用AFM进行光盘质量检测主要有三方面：盘片和模板表面的定性观测;信息位几何结构的半定量分析;信息位特征尺寸的统计分析.定性观测和半定量分析可以对盘片播放的高误差率、凹坑形态和块出错率、凸台形态及其表面粗糙度等参数进行有针对性的检测;而信息位特征尺寸的统计分析则可以对信息位几何结构的关键参数进行面向生产过程的统计分析.所得结论表明AFM在光盘质量检测过程中具有独特的优势.     

Stereoscopic display of atomic force microscope images using anaglyph techniques

This paper describes the use of a standard stereo-pair image display method for presenting the three-dimensional relief information found in atomic force microscope (AFM) images. The method makes use of commercially available image processing software packages. The techniques are illustrated on AFM images of the cuticle structure of a human hair fibre.     

Neural network sliding mode controller of atomic force microscope‐based manipulation with different cantilever probes

Development of nanotechnology has given rise to various applications, including the nano‐manipulation process within small‐size environments. The implementation of such processes requires the use of tools and proper equipment and understanding of various factors influencing it. One such tool is the atomic force microscope (AFM) and its probe, used for imaging surfaces and manipulation tools. The AFM probe is the most important element of the AFM with a key role in system function. The dynamic analysis and control of AFM are necessary to increase efficiency. In this paper, a model of AFM is reviewed and rewritten by considering various cantilever probes, including rectangular, V‐shaped, and dagger. The AFM actuator was modeled and analyzed on uncertain conditions. The position of the stage was controlled to the desired position through the desired motion profiles. To overcome the problem of model nonlinearity, a neural network (NN) sliding mode controller was used to optimize the controller parameter and provide the desired output. The simulation of system was performed by the effective parameters, its control was implemented, and the results were analyzed. The simulation revealed that the modified sliding mode controller with learnable NN improved controller performance by decreasing the rise time and eliminating the overshot.     

计量型原子力显微镜的位移测量系统(英文)

针对纳米结构表征和纳米制造的质量控制需要,中国计量科学研究院设计并搭建了一台计量型原子力显微镜用于纳米几何结构的测量.为了将位移精确溯源到国际单位米,研制了单频8倍程干涉仪测量位移,样品表面形貌则由接触式原子力显微镜测量.一个立方体反射镜与原子力显微镜的测头固定,作为干涉仪的参考镜.两个互相垂直的干涉仪用于测量样品与探针在x-y方向的相对位置.样品台置于具有三面反射镜的零膨胀玻璃块上,由压电陶瓷位移台驱动.另外两台干涉仪测量样品与探针在z方向的位移,探针针尖位于干涉仪光束的交点以减小Abbe误差.由于光学器件的缺陷产生的相位混合会引起非线性误差,采用谐波分离法拟合干涉信号来修正误差,修正后干涉仪测量误差减小为0.7 nm.     

The structure difference of proteins isolated on substrate with different techniques as studied by the atomic force microscope

The height and width of proteins deposited on mica substrates were measured from cross sections of their atomic force microscope (AFM) images. The tapping mode AFM gave very stable and reproducible images for high molecular weight proteins. The following results were obtained: (1) The thickness of mono-, bi-, and trilayered purple membranes was 5.3, 10.4, and 16.0 nm, respectively. The calibration curve of z range of AFM based on the above data was linear. The deviation of the calibration curve at the origin was < 0.6 nm. (2) The height of slow form α-2-macroglobulin (α2M) molecule changed depending on sampling methods. When the protein was freeze-dried on a mica substrate prewetted with water, α2M gave the highest value for its height. The fact that freeze-drying, especially after prewetting of the substrate, was effective to prevent flattening of the molecule suggested that sample deposition must be as gentle as possible to keep the original height of the molecules. (3) Furthermore, we compared differences of height and width between α2M and myosin filament. The result suggested that α2M had a disk-like rather than a spherical form. Large proteins such as α2M are still difficult to crystallize for x-ray analysis, and we tested the AFM method for the study of minute height differences of such proteins.     

光学原子力显微镜中的蒙特卡罗方法

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10nm左右.     

一种高精度多功能双用原子力显微镜技术及应用

主要研究了一种基于高精度IPC-205B型扫描隧道显微镜(STM)的新型高精度多功能双用原子力显微镜(AFM)技术及其应用.阐述该原子力显微镜的工作原理、组成及应用,详细介绍了该AFM镜体的独特结构和新型微悬臂的制作及其检测方法.该AFM采用简单适用的新型微悬臂.并利用STM检测微悬臂的起伏,通过四维机械驱动和双压电陶瓷扫描,有效提高了扫描精度,扩大了扫描范围.该机型集AFM和STM功能为一体,其中STM可以单独使用.该机型检测精度可达:横向0.1 nm,纵向0.01 nm.并用该样机进行了样品表面形貌和隧道谱的实验研究.     

Accurate measurement of the out-of-plane motion of a tip-scanning atomic force microscope

A tip-scanning atomic force microscope (AFM) can be used as a highly accurate height-measuring instrument for large samples, such as liquid crystal displays. To accurately measure the flatness or surface roughness of large samples, the xy-scanner-induced out-of-plane motion must be known to discriminate scanner artifacts from the measured AFM images. As the topographic signals of AFM measurements contain the hysteresis of the z-scanner piezoelectric actuators, actual movements of the z-scanner were measured using a z-axis sensor glued to the actuator. The actual out-of-plane motion of the xy-scanner was found to be less than 1 nm for a 50-μm scan.     

Dynamic friction measurements with an atomic force microscope on polymer surfaces

The combination of scanning friction force microscopy (SFFM) and lock‐in techniques leads to dynamic SFFM (DSFFM) and provides great advantages in friction force studies with sub‐micrometre resolution. In this paper are presented measurements on thin adsorbed organic films on polymers (polymer blend of 75% poly(allylaminehydrochloride) (PAA) and 25% poly(diallyl‐dimethylammonium chloride) (PDDAC)) and on mica (as a reference). The amplitude and phase response as a function of the excitation amplitude can be explained on hard surfaces by a simple static and dynamic friction model. This model allows us further to distinguish static friction forces and kinetic friction forces in a quantitative way. Furthermore, we demonstrate the use of these spectra to determine the correct modulation amplitude of the excitation to achieve the optimal friction contrasts directly. Polymer data suggest that the viscoelastic shear flow under the atomic force microscope (AFM) tip is responsible for the shape of the phase and amplitude spectrum. Lastly, we demonstrate that DSFFM is a useful technique for surface characterisation in situations where SFFM may not be adequate.