扫描探针显微镜在粗糙度、纳米尺寸、表面形貌观测方面的应用

扫描探针显微镜是近十几年来在表面特征表面形貌观测方面最重大的进展之一，是纳米测量学的基本工具，本文叙述了扫描探针显微镜的工作原理、检测模式及在观察检测纳米级的粗糙度、微小尺寸、表面形貌方面的特点和方法，比较了原子力显微镜、常规的表面轮廓仪、干涉显微镜、扫描电子显微镜在表面特性、表面形貌观测方面的性能，着重介绍了扫描探针显微镜在这方面的应用和存在的问题。     

Invited review article: combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science

This is a comprehensive review of the combination of scanning probe microscopy (SPM) with various optical spectroscopies, with a particular focus on Raman spectroscopy. Efforts to combine SPM with optical spectroscopy will be described, and the technical difficulties encountered will be examined. These efforts have so far focused mainly on the development of tip-enhanced Raman spectroscopy, a powerful technique to detect and image chemical signatures with single molecule sensitivity, which will be reviewed. Beyond tip-enhanced Raman spectroscopy and/or topography measurements, combinations of SPM with optical spectroscopy have a great potential in the characterization of structure and quantitative measurements of physical properties, such as mechanical, optical, or electrical properties, in delicate biological samples and nanomaterials. The different approaches to improve the spatial resolution, the chemical sensitivity, and the accuracy of physical properties measurements will be discussed. Applications of such combinations for the characterization of structure, defects, and physical properties in biology and materials science will be reviewed. Due to the versatility of SPM probes for the manipulation and characterization of small and/or delicate samples, this review will mainly focus on the apertureless techniques based on SPM probes.     

Analysis conditions of an industrial Al-Mg-Si alloy by conventional and 3D atom probes.

Industrial 6016 Al-Mg-Si(Cu) alloys are presently regarded as attractive candidates for heat treatable sheet materials. Their mechanical properties can be adjusted for a given application by age hardening of the alloys. The resulting microstructural evolution takes place at the nanometer scale, making the atom probe a well suited instrument to study it. Accuracy of atom probe analysis of these aluminium alloys is a key point for the understanding of the fine scale microstructural evolution. It is known to be strongly dependent on the analysis conditions (such as specimen temperature and pulse fraction) which have been widely studied for ID atom probes. The development of the 3D instruments, as well as the increase of the evaporation pulse repetition rate have led to different analysis conditions, in particular evaporation and detection rates. The influence of various experimental parameters on the accuracy of atom probe data, in particular with regard to hydride formation sensitivity, has been reinvestigated. It is shown that hydrogen contamination is strongly dependent on the electric field at the specimen surface, and that high evaporation rates are beneficial. Conversely, detection rate must be limited to smaller than 0.02 atoms/pulse in order to prevent drastic pile-up effect.     

纳米连接过程的分子动力学模拟研究进展

纳米材料因其特有的结构和性能而得到广泛的应用，纳米连接技术也随之发展起来。在纳米加工领域，虽然有很多先进的显微分析手段，但由于实时观察技术的限制，材料的很多现象和行为很难通过实验进行观测和分析，而分子动力学适用于几纳米到几十纳米的三维空间尺度和纳秒以下的时间尺度，同纳米加工领域很多过程的时间尺度和空间尺度保持一致，因此，利用分子动力学模拟纳米材料性能和连接过程原子的动力学行为是可行的。综述了纳米材料（包括纳米多层膜、纳米线、碳纳米管、纳米颗粒）在纳米连接过程以及连接大尺寸材料过程中的分子动力学模拟研究进展，模拟结果与实验结果基本吻合。结合最新研究进展，讨论了分子动力学模拟在纳米连接应用中的存在问题、解决办法和发展趋势。     

大气状态下SPM纳米加工系统的开发

对现有的商业化SPM进行了一些必要的改造，使其适合于扫描探针加工的要求。讨论了在DI公司多功能SPM基础上开发纳米加工系统的可能性，并提供了一套完整的信号施加，过程监测和环境控制的方法，实现了矢量式的纳米氧化加工，得取了30nm宽的氧化结构，为下一步进行纳米电子器件的构建奠定了基础。     

Transmission electron microscopy as a tool to image bioinorganic nanohybrids: the case of phage-gold nanocomposites

In recent years, bioinorganic nanohybrids composed of biological macromolecules and functional inorganic nanomaterials have revealed many unique properties that show promise for the future. Transmission electron microscopy (TEM) is a popular and relatively simple tool that can offer a direct visualization of the nanomaterials with high resolutions. When TEM is applied to visualize bioinorganic nanohybrids, a treatment of negative staining is necessary due to the presence of biological molecules in the nanohybrids except for those with densely packed inorganic materials. However, the conventional negative-staining procedure for regular biological samples cannot be directly applied to such bioinorganic nanohybrids. To image a specific bioinorganic nanohybrid, negative-staining factors such as negative stain type, working pH, staining time, and drying method, should be identified. Currently, no detailed studies have been done to investigate how to adjust negative-staining factors based on specific bioinorganic nanohybrids. In this study, bacteriophage-gold nanoparticle hybrids were chosen as a model to systematically study the effects of each factor on the negative staining of the nanohybrids. The best staining conditions for gold nanoparticle-phage nanohybrids were obtained and the effects of each factor on the negative staining of general nanohybrids were discussed. This work indicates that with proper staining it is possible to use TEM to visualize directly both biological and inorganic components without introducing any artifact.     

Analysis of scanning probe microscope images using wavelets

The utility of wavelet transforms for analysis of scanning probe images is investigated. Simulated scanning probe images are analyzed using wavelet transforms and compared to a parallel analysis using more conventional Fourier transform techniques. The wavelet method introduced in this paper is particularly useful as an image recognition algorithm to enhance nanoscale objects of a specific scale that may be present in scanning probe images. In its present form, the applied wavelet is optimal for detecting objects with rotational symmetry. The wavelet scheme is applied to the analysis of scanning probe data to better illustrate the advantages that this new analysis tool offers. The wavelet algorithm developed for analysis of scanning probe microscope (SPM) images has been incorporated into the WSxM software which is a versatile freeware SPM analysis package.     

Frictional and adhesive behavior of organic–inorganic hybrid coatings on surgical grade stainless steel using nano-scratching technique

Because of their mechanical properties, metals are the most widely used materials as orthopaedic implants. However they cannot provide a natural bond with the mineralized bone and they also release metallic particles due to degradation or tribologic events. One way to improve the metallic implants performance is to apply protective organic–inorganic sol–gel coatings. In this work, stainless steel substrates are coated with films made by a sol–gel technique from organosilane precursors.Although mechanical properties of similar films have been studied, there is no information about adhesion, friction or deformation processes of silica-based hybrid films to stainless steel substrates.Hybrid coatings with higher amount of inorganic components (called TMH) have almost no elastic response and the debris due to chipping or delamination does not persist into the indentation trace. With the film with high content of organic compounds was found elastic recovery in early stages of loading and there is evidence of pile-up at the edges of the trace with higher load applied. After the unloading the film has a persistent deformation and is removed due to the asynchronic recovery of the film and the substrate. The combined two-film coating shows a lot of debris in the trace. This is an unusual but possible behavior of polymeric coatings and could be attributed to different recoveries between the first inorganic layer (called TEOS–MTES), the substrate and the upper TMH film. This fact produces delamination and crack formation in the TEOS–MTES coating, inducing tensile efforts, and finally the upper film is pulled-off.     

Reducing the missing wedge: High-resolution dual axis tomography of inorganic materials

Electron tomography is a powerful technique that can probe the three-dimensional (3-D) structure of materials. Recently, this technique has been successfully applied to inorganic materials using Z-contrast imaging in a scanning transmission electron microscope to image nanomaterials in 3-D with a resolution of 1 nm in all three spatial dimensions. However, an artifact intrinsic to this technique limits the amount of information obtainable from any object, namely the missing wedge. One way to circumvent this problem is to acquire data from two perpendicular tilt axes, a technique called "dual axis tomography." This paper presents the first dual axis data at high resolution for inorganic materials, and by studying a CdTe tetrapod sample, demonstrates the increase in information obtained using this technique.     

扫描离子电导显微镜技术及其在纳米生物学研究中的应用

扫描探针显微镜技术的出现开辟生命科学研究的新纪元并逐步发展成为在纳米尺度研究细胞结构与功能的一类新型的显微镜技术。扫描离子电导显微镜技术就是新近发展起来的这一扫描探针显微镜技术家族中的一员,可被用来在生理条件下、高分辨率及非接触地研究活细胞的表面形貌,从而帮助人们深入研究细胞微观结构与功能的关系。本文简要介绍扫描离子电导显微镜技术的基本原理,并结合国外研究现状综述该技术在纳米生物学研究中的应用。     

EXPERIMENTAL RESEARCH OF NANO-CUTTING BY USING SCANNIN G PROBE MICROCOPE

0 INTRODUCTIONNanotechnolOgy becomes particularly interestingnowadays, because the increasing needs of itsapplications are demanded with the development ofhish technology, not only in scientific but also inengineering field, esPecialy in electronic and opticalindustries. As long as nanotechnology is mentioned, itwill be concerned that machining at nanometer scale,which is sometimes called "nanomachining". Thereare two similar ultra-precision machining inconventional method, i. e. ultrapre…     

纳米操作加工过程定位检测问题研究

微纳米操作、加工、检测和控制在各个领域获得广泛的研究和应用,在微纳米层次上进行原位、定位的操作、检测、加工是经常遇到的问题。扫描探针显微镜技术(Scanningprobemicroscope,SPM)提供强有力的工具,人们利用其不同类型的针尖与相应样品表面产生的化学或物理作用达到目的。但扫描探针显微镜针尖同时用于检测、加工和成像,会因为针尖磨损、状态的改变,影响检测信息的准确性、可靠性,直接影响结果的判定。本文提出一种在微操作加工过程的定位检测技术,即操作过程工具和探针承担不同任务,工具负责加工操作,探针用于检测并定位于操作加工位置,进行了实验并分析讨论定位过程相关问题。     

High-speed force load in force measurement in liquid using scanning probe microscope

This article presents an inversion-based iterative feedforward-feedback (II-FF/FB) approach to achieve high-speed force load in force measurement of soft materials in liquid using scanning probe microscope (SPM). SPM force measurement under liquid environment is needed to interrogate a wide range of soft materials, particularly live biological samples. Moreover, when dynamic evolution of the sample occurs during the measurement, and/or measuring the rate-dependent viscoelasticity of the sample, the force measurement also needs to be acquired at high-speed. Precision force load in liquid, however, is challenged by adverse effects including the thermal drift effect, the reduction of the signal to noise ratio, the distributive hydrodynamic force effect, and the hysteresis and vibrational dynamics effects of the piezoelectric actuators (for positioning the probe relative to the sample), particularly during high-speed measurement. Thus, the main contribution of the article is the development of the II-FF/FB approach to tackle these challenges. The proposed method is illustrated through an experimental implementation to the force-curve measurement of a poly (dimethylsiloxane) sample in liquid at high-speed.     

纳米加工和材料去除机理研究

针对钠米技术、微型机械在未来工程应用中对纳米级加工的要求,提出将扫描探针显微镜的技术和原理应用于纳米机械加工过程,实现纳米量级加工的可控性和加工结果的可观察性。给出了采用该方法进行纳米切削加工的试验结果,表明这一方法具有稳定、可靠的微加工性能。观察结果显示了材料去除加工的微观过程,被去除材料在刃前发生剪切变形前,与之约成90°的前刀面方向上切屑已充分变形。     

A systematic investigation of the charging effect in scanning electron microscopy for metal nanostructures on insulating substrates

Scanning electron microscopy is perhaps the most important method for investigating and characterizing nanostructures. A well‐known challenge in scanning electron microscopy is the investigation of insulating materials. As insulating materials do not provide a path to ground they accumulate charge, evident as image drift and image distortions. In previous work, we have seen that sample charging in arrays of metal nanoparticles on glass substrates leads to a shrinkage effect, resulting in a measurement error in the nanoparticle dimension of up to 15% at 10 kV and a probe current of 80 ± 10 pA. In order to investigate this effect in detail, we have fabricated metal nanostructures on insulating borosilicate glass using electron beam lithography. Electron beam lithography allows us to tailor the design of our metal nanostructures and the area coverage. The measurements are carried out using two commonly available secondary electron detectors in scanning electron microscopes, namely, an InLens‐ and an Everhart–Thornley detector. We identify and discriminate several contributions to the effect by varying microscope settings, including the size of the aperture, the beam current, the working distance and the acceleration voltage. We image metal nanostructures of various sizes and geometries, investigating the influence of scan‐direction of the electron beam and secondary electron detector used for imaging. The relative measurement error, which we measure as high as 20% for some settings, is found to depend on the acceleration voltage and the type of secondary electron detector used for imaging. In particular, the Everhart–Thornley detectors lower sensitivity to SE₁ electrons increase the magnitude of the shrinkage of up to 10% relative to the InLens measurements. Finally, a method for estimating charge balance in insulating samples is presented.     

Synthesis and microtribological studies of new silica–triazine hybrids

Synthesis of organic/inorganic hybrid materials is an area of growing interest as advantageous properties of disparate components can be combined into singular materials. In this study, nanosized silica gel hybrids were obtained by reaction between silanol groups of silica and 2,4-dichloro-6-methoxy-1,3,5-triazine (DCMT), which then reacted with p-phenylenediamine. Acylation of amine by 10-undecanoic acid, N-Fmoc-Lys(Boc)OH, and N-Boc-Ser(OH)OH was the final step. Friction performance of silica–triazine hybrids, evaluated with a microtribometer, can be ranked in the following order: 10-undecanoic acid >N-Fmoc-Lys(Boc)OH>p-phenylenediamine>N-Boc-Ser(OH)OH. It is inferred that all the hybrids are effective in reducing friction, in comparison to pure silica materials. The rearrangement of silica–triazine hybrid included the 10-undecanoic acid, induced by UV exposure, also confirmed further improvement of friction performance. This approach can be successfully applied to preparation of other ORMOSIL hybrids.     

Atomic force microscope (AFM) combined with the ultramicrotome: a novel device for the serial section tomography and AFM/TEM complementary structural analysis of biological and polymer samples

A new device (NTEGRA Tomo) that is based on the integration of the scanning probe microscope (SPM) (NT‐MDT NTEGRA SPM) and the Ultramicrotome (Leica UC6NT) is presented. This integration enables the direct monitoring of a block face surface immediately following each sectioning cycle of ultramicrotome sectioning procedure. Consequently, this device can be applied for a serial section tomography of the wide range of biological and polymer materials. The automation of the sectioning/scanning cycle allows one to acquire up to 10 consecutive sectioned layer images per hour. It also permits to build a 3‐D nanotomography image reconstructed from several tens of layer images within one measurement session. The thickness of the layers can be varied from 20 to 2000 nm, and can be controlled directly by its interference colour in water. Additionally, the NTEGRA Tomo with its nanometer resolution is a valid instrument narrowing and highlighting an area of special interest within volume of the sample. For embedded biological objects the ultimate resolution of SPM mostly depends on the quality of macromolecular preservation of the biomaterial during sample preparation procedure. For most polymer materials it is comparable to transmission electron microscopy (TEM). The NTEGRA Tomo can routinely collect complementary AFM and TEM images. The block face of biological or polymer sample is investigated by AFM, whereas the last ultrathin section is analyzed with TEM after a staining procedure. Using the combination of both of these ultrastructural methods for the analysis of the same particular organelle or polymer constituent leads to a breakthrough in AFM/TEM image interpretation. Finally, new complementary aspects of the object's ultrastructure can be revealed.     

Soft X‐ray spectromicroscopy for speciation,quantitation and nano‐eco‐toxicology of nanomaterials

There is a critical need for methods that provide simultaneous detection, identification, quantitation and visualization of nanomaterials at their interface with biological and environmental systems. The approach should allow speciation as well as elemental analysis. Using the intrinsic X‐ray absorption properties, soft X‐ray scanning transmission X‐ray spectromicroscopy (STXM) allows characterization and imaging of a broad range of nanomaterials, including metals, oxides and organic materials, and at the same time is able to provide detailed mapping of biological components. Thus, STXM offers considerable potential for application to research on nanomaterials in biology and the environment. The potential and limitations of STXM in this context are discussed using a range of examples, focusing on the interaction of nanomaterials with microbial cells, biofilms and extracellular polymers. The studies outlined include speciation and mapping of metal‐containing nanomaterials (Ti, Ni, Cu) and carbon‐based nanomaterials (multiwalled carbon nanotubes, C₆₀ fullerene). The benefits of X‐ray fluorescence detection in soft X‐ray STXM are illustrated with a study of low levels of Ni in a natural river biofilm.     

Whispering-gallery acoustic sensing: characterization of mesoscopic films and scanning probe microscopy applications

Full understanding of the physics underlying the striking changes in viscoelasticity, relaxation time, and phase transitions that mesoscopic fluid-like films undergo at solid-liquid interfaces, or under confinement between two sliding solid boundaries, constitutes one of the major challenges in condensed matter physics. Their role in the imaging process of solid substrates by scanning probe microscopy (SPM) is also currently controversial. Aiming at improving the reliability and versatility of instrumentation dedicated to characterize mesoscopic films, a noninvasive whispering-gallery acoustic sensing (WGAS) technique is introduced; its application as feedback control in SPM is also demonstrated. To illustrate its working principle and potential merits, WGAS has been integrated into a SPM that uses a sharp tip attached to an electrically driven 32-kHz piezoelectric tuning fork (TF), the latter also tighten to the operating microscope's frame. Such TF-based SPMs typically monitor the TF's state of motion by electrical means, hence subjected to the effects caused by the inherent capacitance of the device (i.e., electrical resonance differing from the probe's mechanical resonance). Instead, the novelty of WGAS resides in exploiting the already existent microscope's frame as an acoustic cavity (its few centimeter-sized perimeter closely matching the operating acoustic wavelength) where standing-waves (generated by the nanometer-sized oscillations of the TF's tines) are sensitively detected by an acoustic transducer (the latter judiciously placed around the microscope's frame perimeter for attaining maximum detection). This way, WGAS is able to remote monitoring, via acoustic means, the nanometer-sized amplitude motion of the TF's tines. (This remote-detection method resembles the ability to hear faint, but still clear, levels of sound at the galleries of a cathedral, despite the extraordinary distance location of the sound source.) In applications aiming at characterizing the dynamics of fluid-like mesoscopic films trapped under shear between the TF probe and the solid substrate, WGAS capitalizes on the well-known fact that the TF's motion is sensitively affected by the shear-forces (the substrate and its adsorbed mesocopic film playing a role) exert on its tip, which occurs when the latter is placed in close proximity to a solid substrate. Thus, WGAS uses a TF as an efficient transducer sandwiched between (i) the probe (that interact with the substrate and mesoscopic film), and (ii) the acoustic cavity (where an assessment of the probe mechanical motion is obtained). In short, WGAS has capability for monitoring probe-sample shear-force interactions via remote acoustic sensing means. In another application, WGAS can also be used as feedback control of the probe's vertical position in SPM. In effect, it is observed that when the microscope's probe stylus approaches a sample, a monotonic change of the WGAS acoustic signal occurs in the last ~20 nm before the probe touches the solid sample's surface, which allows implementing an automated-control of the probe-sample distance for safely scanning the tip across the sample surface. This principle is demonstrated by imaging the topographic features of a standard sample. Finally, it is worth to highlight that this alignment-free acoustic-based method offers a very direct assessment of the probe's mechanical motion state (the mechanical and the WGAS acoustic frequency responses coincide), which makes the WGAS a convenient metrology tool for studying surface interactions, including interfacial friction at the nanometer scale.     

High sensitivity image intensifier-TV detector for x-ray diffraction studies

A sensitive, efficient image intensifier-TV x-ray detector is described that has been optimized for a large class of diffraction studies of biological structures. All of the major components are commercially available. The system is well suited to measuring the intensity of diffraction patterns that are weak, or changing with time. Because there is no count rate limitation, it is particularly well suited for studies utilizing the high fluxes of synchrotron sources.