间歇模原子力显微镜非线性振动的数值模拟

1　引　言　　原子力显微镜 (简记为 AFM)是利用其微悬臂梁的机械振动响应于力敏探针和实验样品表面之间的相互作用力来成像的 ,由于具有原子和分子级的分辨率 ,已成为表面成像及材料微结构研究的新工具 ,在科学技术的各种领域获得了广泛的应用 [1-2 ] 。有几种不同模式的 AFM相继被开发使用。在 AFM的接触模工作中 ,其力敏探针始终保持同样品表面相接触 ,力敏探针和样品之间的相互作用力被微悬臂梁位移产生的弹性力所平衡 ,这种接触模式有极高的分辨率 ,但力敏探针上存在横向力 ,对实验样品有较大的损伤 ;在 AFM的非接触模工作中 ,力…     

用于减小控制对测量影响的AFM新工作模式

原子力显微镜（atomic force microscope，AFM）是纳米尺度线宽成像和测量的重要工具．但系统的非线性和控制器参数选择的多样性导致AFM控制的不确定性，影响了AFM测量结果的精确性和重复性．为克服这个缺点，分析了AFM的测量原理和工作模式的特点，在此基础上提出了一种新的工作模式——补偿模式．在这种工作模式中，结合了扫描器和悬臂梁的位置信息而得到被测试样表面的形貌图像．与恒力接触模式相比，在补偿模式下，AFM能够在高速度下以更好的精确性和重复性进行成像和测量．仿真和实验结果证明了这种新工作模式的可行性和适用性．实验结果说明该工作模式可以提高扫描速度16倍或减小均方根误差到约1／5．     

AFM扫描图像重构算法的改进

针对原子力显微镜（AFM）纳米成像中存在的失真问题,研究了通过探针建模实现AFM扫描图像重构方法.目前探针盲建模算法在重构AFM图像时存在较大误差,因此提出基于探针模型预估计的AFM扫描图像重构方法.该方法采用分区探针针尖建模,并通过基于该探针模型的反卷积运算实现AFM扫描图像重构,获得比较接近真实形貌的AFM扫描图像.文中介绍了算法的具体步骤,通过仿真和实验结果证明,该方法能够有效降低AFM图像重构时引入的误差,得到的图像更能反映样品表面真实的形貌.     

一个基于直方图的纳米尺度线宽计算模型

用原子力显微镜 (AFM )来测量纳米线宽近几年发展迅速。针对AFM能对纳米线宽表面三维成像的特点 ,本文提出了一个直方图线宽计算模型 ,并通过实验数据同其他模型进行了比较。该线宽计算模型具有算法简单、抗干扰能力强的优点     

AFM轻敲模式下扫描参数对成像质量影响的研究

针对原子力显微镜(AFM)扫描参数对成像质量的影响规律,对现有的扫描参数影响成像质量的研究进行了分析。提出了以幅值误差作为评价AFM成像质量的指标,通过实验研究了扫描参数对AFM成像质量的耦合影响。发现了扫描频率fs、积分增益I和幅值设定点S这3个扫描参数间相互影响的现象,在S低较低情况下可设置更大的fs和I,在获取高质量成像的同时,提升了测量效率,对扫描参数的合理设置提供了可靠的操作准则。     

基于压电扫描管动态特性分析的AFM成像方法研究

针对原子力显微镜(AFM)在高速扫描下成像误差大的缺点,提出了一种基于压电扫描管动态特性的改进成像方法,并对这种成像方法的性能进行了理论分析和实验验证.分析和实验结果表明,该成像方法可以较好地处理压电扫描管的动态特性,有效地提高 AFM 在 Z 方向上的成像精度,因此得到的扫描图像能够更加真实地反映样品的形貌.     

上浆剂分子量对碳纤维表观性能及其界面性能影响研究

研究了不同分子量的上浆剂对碳纤维表观状态及其界面性能的影响,并采用了AFM,SEM等表面分析技术研究了上浆后碳纤维表面形貌.AFM,SEM证实了S-1表面没有小颗粒存在,沟槽较均匀,而S-2表面的沟槽较深,S-3表面的沟槽较浅,且表面都有小的颗粒.XPS证实了S-1表面含有O元素含量最高,表面极性官能团较多.上浆剂分子...     

O.92PZN-0.08PT晶体的缺陷与畴结构研究

应用环境扫描电子显微术(ESEM)、原子力扫描显微术(AFM)、同步辐射白光形貌术(SRWBT)等形貌成像技术研究了0.92PZN-0.08PT晶体的表面缺陷形态与铁电畴结构.通过对畴结构动态演化的同步辐射形貌观察,可揭示出该晶体的结构相变过程.     

基于条件生成式对抗网络的AFM图像盲重构方法

针对原子力显微镜（AFM）成像过程中针尖展宽效应引起的误差,提出一种基于条件生成式对抗网络（CGAN）的AFM图像盲重构方法。首先,以pix2pixHD模型为基础,通过全局生成网络对仿真样本数据进行对抗训练,引入AFM测量数据采用局部提升网络联合训练;最后,特征匹配损失函数以用于提升栅格边缘横向分辨力。实验结果表明:对于线宽8μm一维矩形栅格在AFM下的测量图像进行盲重构,重构图像标准差为0.33μm×0.45μm,具有较高的成像分辨力,有利于提升AFM图像一维栅格测量的准确度。     

XPS,AFM研究沥青基碳纤维电化学表面处理过程的机制

对各向同性沥青基碳纤维进行电化学氧化表面处理,用XPS,AFM分析了碳纤维表面含氧官能团和表面微观形貌的变化过程。实验结果表明:电化学氧化处理是表面碳及其含氧官能团逐步被氧化成羧基和CO₂的过程。氧化处理首先是使碳纤维表面变得更光滑,持续氧化后才会出现沟槽,SEM的分辨率不足以表征碳纤维电化学氧化前后的表面形貌变化,而采用AFM可在纳米尺度上表征碳纤维在电化学氧化过程中的表面形貌变化。AFM和XPS的结合可表征碳纤维电化学氧化表面处理的进程。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.