Near-Field Scanning Optical Microscopy Combined with a Tapping Mode Atomic Force Microscope

Tapping mode atomic force microscopy is used to control the tip-sample distance in near field scanning optical microscopy (NSOM), which gives both topographic and near-field images simultaneously. The evanescent waves are scattered by a vibrating silicon-nitride tip in the proximity of sample surfaces and are detected through a microscope objective. This NSOM allows the observation of opaque samples with reflection illumination. A glass grating of 1-μm pitch and an InP grating of 0.5-μm pitch are observed with a lateral resolution of 100 nm.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan     

原子力显微术轻敲模式中探针样品接触过程及相位衬度研究

借助简单的有阻尼受迫振子模型,研究了原子力显微术轻敲模式中探针与样品接触时间t_c、样品的表面形变D_z和相位衬度对探针设置高度z_c及样品杨氏模量E_s的依赖关系.结果发现,t_c与D_z均随E_s及z_c的增大而减小,同时探针与样品作用过程伴随很小的能量耗散.对轻敲过程中相移量φ的研究表明,E_s较大的样品有较小的φ,且φ随关键词：原子力显微术轻敲模式相位衬度     

MeV-ion-induced defects in organic crystals

We present scanning force microscope images of crater-like defects induced by MeV atomic ions incident on single-crystal L-valine surfaces. For grazing incidence ions, the craters are elongated alongthe ion azimuth of incidence and are followed by raised tails in the surface above the ion track. Craters formed by off-normal ions are wider than craters formed by nrmally incident ions. The crater volume is highly nonlinear in (dE/dx)_e. We discuss our observations qualitatively in terms of thermal-spike and pressure-pulse/shock-wave models for the sputtering of organic solids.     

原子力显微镜及其对DNA大分子的应用研究

详细讨论了原子力显微镜的基本原理和针尖－样品间相互作用力,大量实验结果表明,ＡＦＭ这个高分辨成像技术对ＤＮＡ大分子进行应用研究是非常适合的,同时我们也讨论了样品制备方法的改进、成像模式和环境选择等因素对ＤＮＡ大分子ＡＦＭ结果的影响以及ＡＦＭ在ＤＮＡ分子结构研究中的一些局限性。     

Dynamic scanning force microscopy at low temperatures on a van der Waals surface: graphite (0001)

The (0001) surface of highly oriented pyrolytic graphite is studied by scanning force microscopy in both contact and dynamic mode. Low temperatures were necessary for the dynamic mode measurements in order to achieve the required signal to noise ratio. At 22 K, atomic scale structures with 2.46 Å periodicity and trigonal symmetry of the individual maxima were obtained in both modes. Since graphite exhibits a van der Waals surface in good approximation, this result shows that comparatively weak forces of van der Waals type are sufficient for successful imaging in the dynamic mode on the atomic scale. However, since the positions of the observed maxima correspond to the ones found by scanning tunneling microscopy and contact scanning force microscopy, but not to the positions of the carbon atoms, it also opens new questions on the imaging mechanism in the dynamic mode.     

Effect of chain length on the adhesion behaviour of n-alkanethiol self-assembled monolayers on Au(111): An atomic force microscopy study

The effect of chain length on the adhesion behaviour of n-alkanethiols CH₃(CH₂)_nSH, wheren = 5, 6, 7, 9, 10, 11, 14 and 15 has been followed by carrying out pull-off force measurement using atomic force microscopy (AFM). The self-assembled monolayers on Au(111) surface has been characterized by reflection absorption infra-red spectroscopy (RAIRS) and contact mode AFM. It is observed that the work of adhesion is independent of thiol chain length though the standard deviation is high for short chain length thiol-based monolayers. This may be attributed to the relatively more deformable nature of the short chain thiol films due to their heterogeneity in the monolayer structure than the long chain ones. This, in turn, increases the contact area/volume between the AFM tip and the monolayer, and hence the force of adhesion. However, in the presence of water, the force of adhesion is lower than that observed in air reflecting the effects of capillary forces/polar components associated with the surface energy.     

Electrical Measurement Techniques in Atomic Force Microscopy

A conductive tip in an atomic force microscope (AFM) has extended the capability from conventional topographic imaging to electrical surface characterization. The conductive tip acts as a voltage electrode to provide stimuli and monitor electrical surface properties. In this review article, we have organized the AFM electrical techniques based on whether the electrical properties are monitored at the cantilever tip or across the sample. Furthermore, the techniques are organized based on probe detection signal. A number of acronyms are used in the literature, and the more commonly used ones are identified. The principle of each technique is described, and representative applications are presented. A better understanding of the spectrum of techniques should serve as the driver to expand the application of electrical techniques to study interdisciplinary phenomena at the nanoscale.     

原子力显微镜加工轨迹测压电剪切叠堆二维高频运动位移

针对两轴压电剪切叠堆在高频电压驱动下的二维高频运动的位移测量问题,提出使用（AFM）探针在敲击模式下的加工痕迹测量压电剪切叠堆运动位移的方法,首先制备热塑性聚合物聚甲基丙烯酸甲酯（PMMA）薄膜,随后进行AFM探针敲击加工实验,扫描AMF探针加工轨迹并对其进行后处理,成功得到压电剪切叠堆的二维高频运动位移,实现了以半接触的方式对压电剪切叠堆二维高频复杂运动的准确检测,并依据实验数据对压电剪切叠堆二维运动位移随电压幅值及频率的变化情况进行分析。实验结果表明,在10 Hz～5 kHz的激励信号频率范围内,所提出的方法能准确测量压电剪切叠堆的运动位移。     

原子力显微镜扫描成像DNA分子

采用Mg2+处理DNA、APTES或戊二醛修饰云母表面、DNA拉直方法制备了λ-DNA及DNA-组蛋白复合物样品.室温下原子力显微镜以轻敲模式在空气中扫描样品成像.实验结果表明:AFM扫描成像的效果与样品的制备方法有关,同时也受操作因素影响.     

The formation of a dislocation spiral on the (101) face of a monoclinic lysozyme crystal: High-resolution experiments

The elementary processes of crystal growth in the case of a low kink density on step edges have been studied by in situ atomic force microscopy. High-resolution images of the first turn of the polygonal dislocation spiral on the (101) face of monoclinic lysozyme crystals, which allow one to discern separate crystal cells, have been obtained. It has been shown that the dependence of the spiral segment velocity on its length is inconsistent with the Gibbs-Thomson law and is represented by several rectilinear sections. The results were explained by taking into account the features of the growth of crystals with a low kink density at low supersaturation.     

Effects of Sm substitution on ferroelectric domains and conductivity in bismuth ferrite ceramics

The large piezoelectric coefficient and multiferroicity of bismuth ferrite (BFO) make it an attractive candidate for lead-free ferroelectric devices. However, large leakage currents have limited broader applications. Rare-earth substitutions in BFO have been shown to improve ferroelectric and magnetic properties. In this work, we employed piezoresponse and conductive atomic force microscopy to study ferroelectric domains in Bi_1-xSm_xFeO₃ (x = 0–0.150) grown by the co-precipitation method. The combined piezoresponse and conductivity measurements can directly visualize the local ferroelectric domains under different sample bias. At Sm mol% > 7.5, Sm-substitution effectively lowers defect-generated conductivity. At Sm mol% < 7.5, conductivity increases due to conductive domain walls inside sample grains. The surfaces of these conductive samples exhibit a p-type rectifying behavior while the bulk is n-type. Our work details how the local piezoelectric properties and transport behaviors of BFO ceramics change as a function of Sm-substitution.     

Imitation of non-contact mode while scanning in the presence of an electric double layer?

Non-contact atomic force microscopy (NCAFM) minimizes the physical interaction between the AFM tip and the surface of interest. Several recent studies have reported observation of single atom defects using this technique. The repulsive force is presumably the primary interatomic force (cf. our paper on pseudo-non-contact mode in this issue) responsible for the reported atomic resolution in these studies. The combination of these factors, minimal tip–sample deformation and repulsive force interaction, are responsible for the observation of the single atom defects. In the present study, we show that similar resolution can be achieved utilizing the same two factors but which employs scanning in a surfactant. The method decreases the tip–sample interaction by eliminating the attractive forces between the tip and sample. The surfactant solution induces an electrical double-layer (EDL) on the surface of the tip and sample. This EDL creates additional repulsion that is distributed over a large area, and hence does not contribute noticeably to the image contrast during scanning. However, it does compensate for the high pressures normally experienced by the tip in the absence of surfactant. In addition, the presence of the EDL enhances tip stability during the image scan. This method has been tested on surfaces of such minerals as mica, chlorite, and anhydrite.     

Effects of ion damage on the surface of ITO films during plasma treatment

During a surface treatment using CF₄/O₂ gas plasma, energetic ions affected the defect structures on the top surface of ITO thin films. C-AFM and local I-V measurements showed the formation of the depleted layer after a plasma treatment with a bias of 20 W; XPS showed the creation of new defect structures. Donor concentration in the damaged top surface of the ITO films was found to be decreased. Sn-based neutral defect complexes and reduced oxygen, which could trap the electrons, have been proposed to be formed. This can also explain the increase of the work function of ITO.