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.     

MEMS-based fast scanning probe microscopes

Scanning probe microscopy is a frequently used nanometer-scale surface investigation technique. Unfortunately, its applicability is limited by the relatively low image acquisition speed, typically seconds to minutes per image. Higher imaging speeds are desirable for rapid inspection of samples and for the study of a range of dynamic surface processes, such as catalysis and crystal growth. We have designed a new high-speed scanning probe microscope (SPM) based on micro-electro mechanical systems (MEMS). MEMS are small, typically micrometer size devices that can be designed to perform the scanning motion required in an SPM system. These devices can be optimized to have high resonance frequencies (up to the MHz range) and have very low mass (10⁻¹¹ kg). Therefore, MEMS can perform fast scanning motion without exciting resonances in the mechanical loop of the SPM, and hence scan the surface without causing the image distortion from which conventional piezo scanners suffer. We have designed a MEMS z-scanner which we have integrated in commercial AFM (atomic force microscope) and STM (scanning tunneling microscope) setups. We show the first successful AFM experiments.     

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.     

Three-dimensional imaging of undercut and sidewall structures by atomic force microscopy

Sidewall surface roughness is an important parameter in electronic device manufacture. At present, no high resolution technique exists to quantitatively characterize this property for undercut structures created by semiconductor processing techniques. We developed a three-dimensional atomic force microscope (3D-AFM) to measure the surface roughness of undercut sidewalls with nanometer precision. Decoupled from the positional scanner, the 3D-AFM probe had a variable tilt up to 40° off the normal. Nonorthogonal scans resolved the sidewall surface roughness, base width, and acute critical angle for undercut structures, including a metal overhang and the transmission line of a photonic device. Compatible with standard cantilevers, the 3D-AFM demonstrates great potential for characterizing the sidewalls of soft materials such as photoresist.     

扫描探针显微镜的进展

扫描探针显微镜（SPMs）经过近30年的发展，已经应用到科学研究的各个方面。为适应不同研究的需要，扫描探针显微镜本身的发展也非常迅速。如其中原子力显微镜（AFM）从发明初期的单一的接触工作模式发展到包括可以测量粘弹性的相位模式在内的多种工作模式，同时通用型方面也高度发展，已经形成了一个庞大的高度自动化的扫描探针显微镜的家族。在这个家族中，严格环境控制的扫描探针显微镜的出现，很好的解决了各种务件下对样品的原位观察，环控化扫描探针显微镜的发展已经引起了人们的足够重视，必将成为扫描探针显微镜发展的一个重要方向。新近出现的各种显微镜集成的扫描探针显微镜系列是这个家族中的新成员，这个成员可以同时完成大范围、高分辨和精确定位等各种研究，必将在半导体制造厂的异物检查、金属和绝缘体等表面测定以及生物大分子研究等领域发挥重要作用。扫描探针显微镜的发明和发展促进了一门新兴的高科技——一纳米科学技术的诞生，宣告一个科枝新纪元，纳米科技时代已经来临。     

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。     

Flexible drift-compensation system for precise 3D force mapping in severe drift environments

The acquisition of dense 3D data sets is of great importance, but also a challenge for scanning probe microscopy (SPM). Thermal drift often induces severe distortions in the data, which usually constrains the acquisition of dense data sets to experiments under ultra-high vacuum and low-temperature conditions. Atom tracking is an elegant approach to compensate for thermal drift and to position the microscope tip with highest precision. Here, we present a flexible drift compensation system which can easily be connected to existing SPM hardware. Furthermore, we describe a 3D data acquisition and position correction protocol, which is capable of handling large and non-linear drift as typically present in room temperature measurements. This protocol is based on atom-tracking for precise positioning of the tip and we are able to acquire dense 3D data sets over several hours at room temperature. The performance of the protocol is demonstrated by presenting 3D data taken on a CaCO(3)(10 ?14) surface with the data density being as large as 85×85×500 pixel.     

High-resolution scanning near-field EBIC microscopy: application to the characterisation of a shallow ion implanted p+-n silicon junction

High-resolution electron beam induced current (EBIC) analyses were carried out on a shallow ion implanted p⁺–n silicon junction in a scanning electron microscope (SEM) and a scanning probe microscope (SPM) hybrid system. With this scanning near-field EBIC microscope, a sample can be conventionally imaged by SEM, its local topography investigated by SPM and high-resolution EBIC image simultaneously obtained. It is shown that the EBIC imaging capabilities of this combined instrument allows the study of p–n junctions with a resolution of about 20 nm.     

Traceable calibration of transfer standards for scanning probe microscopy

A Metrological Atomic Force Microscope (MAFM) has been constructed for the traceable calibration of transfer standards for scanning probe microscopy. It uses optical interferometry to generate image scales with direct traceability to the national standard of length. Three interferometers monitor the relative displacements of the AFM tip and sample in the x, y and z directions and the interferometer data is used directly to construct 3D images of sample surfaces. Traceable dimensional measurement of surface features may then be derived from the image data. This paper describes the MAFM instrument and presents a measurement uncertainty budget. Examples are given of measurements of pitch and step height on calibration transfer standards for scanning probe microscopy.     

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。     

模块化扫描探针显微镜的研究

介绍一种多功能、模块化扫描探针显微镜,它综合了ＳＴＭ、ＡＦＭ、ＭＦＭ、ＦＦＭ等的功能,不仅能检测物质表面微观形貌,还能检测微小静电力、磁力、原子力和摩擦力,具有较好的灵活性和较宽的应用范围。     

Scanning probe microscopy of biological samples and other surfaces

Scanning probe microscopes derived from the scanning tunnelling microscope (STM) offer new ways to examine surfaces of biological samples and technologically important materials. The surfaces of conductive and semiconductive samples can readily be imaged with the STM. Unfortunately, most surfaces are not conductive. Three alternative approaches were used in our laboratory to image such surfaces. 1. Crystals of an amino acid were imaged with the atomic force microscope (AFM) to molecular resolution with a force of order 10^?8 N. However, it appears that for most biological systems to be imaged, the atomic force microscope should be able to operate at forces at least one and perhaps several orders of magnitude smaller. The substitution of optical detection of the cantilever bending for the measurement by electron tunnelling improved the reliability of the instrument considerably. 2. Conductive replicas of non-conductive surfaces enabled the imaging of biological surfaces with an STM with a lateral resolution comparable to that of the transmission electron microscope. Unlike the transmission electron microscope, the STM also measures the heights of the features. 3. The scanning ion conductance microscope scans a micropipette with an opening diameter of 0·04-0·1 μm at constant ionic conductance over a surface covered with a conducting solution (e.g., the surface of plant leaves in saline solution).     

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 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.     

The FAST module: an add-on unit for driving commercial scanning probe microscopes at video rate and beyond

We present the design and the performance of the FAST (Fast Acquisition of SPM Timeseries) module, an add-on instrument that can drive commercial scanning probe microscopes (SPM) at and beyond video rate image frequencies. In the design of this module, we adopted and integrated several technical solutions previously proposed by different groups in order to overcome the problems encountered when driving SPMs at high scanning frequencies. The fast probe motion control and signal acquisition are implemented in a way that is totally transparent to the existing control electronics, allowing the user to switch immediately and seamlessly to the fast scanning mode when imaging in the conventional slow mode. The unit provides a completely non-invasive, fast scanning upgrade to common SPM instruments that are not specifically designed for high speed scanning. To test its performance, we used this module to drive a commercial scanning tunneling microscope (STM) system in a quasi-constant height mode to frame rates of 100 Hz and above, demonstrating extremely stable and high resolution imaging capabilities. The module is extremely versatile and its application is not limited to STM setups but can, in principle, be generalized to any scanning probe instrument.     

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.     

Atomic force microscopy of purple membranes

The surface structure of purple membranes was imaged using an atomic force probe mounted in a scanning tunnelling microscope. One of the two different membrane surfaces showed protruding, disc-shaped features forming an hexagonal lattice with about 6 nm centre to centre spacing. These are identified as the cytoplasmic surfaces of trimers of bacteriorhodopsin molecules and are correlated with the structural information on bacteriorhodopsin obtained from numerous earlier electron microscope and diffraction studies.     

Microtribological applications of probe microscopy

This paper introduces the new field of microtribology; it gives a general overview and then presents some typical research results. Micromachines use very lightweight sliding parts, and their wear is primarily due to surface interaction forces rather than load or weight. The ultimate goal of microtribology is to create practical zero-wear devices. Microtribological evaluations of surfaces have started using new tools, such as the scanning probe microscope. Quasi-static indentation tests, impact indentation tests, line scratch tests, and scanning scratch tests have been performed using an atomic force microscope with a diamond tip. Frictional force distributions and adhesive force distributions have also been obtained using atomic force microscopes. Water clusters adsorbed onto solid surfaces have been observed using a scanning tunnelling microscope. The configuration, adsorption, and mobility of lubricant molecules have also been evaluated using a scanning tunnelling microscope.     

Optimal design and fabrication of three-dimensional calibration specimens for scanning probe microscopy

Micro-/nano-scale roughness specimens are highly demanded to synthetically calibrate the scanning probe microscopy (SPM) instrument. In this study, three-dimensional (3D) specimens with controllable main surface evaluation parameters were designed. In order to improve the design accuracy, the genetic algorithm was introduced into the conventional digital filter method. A primary 3D calibration specimen with the dimension of 10 μm × 10 μm was fabricated by electron beam lithography. Atomic force microscopy characterizations demonstrated that the statistical and spectral parameters of the fabricated specimen match well with the designed values. Such a kind of 3D specimens has the potential to calibrate the SPM for applications in quantitative surface evaluations.     

基于SPM的纳米加工技术研究进展

扫描探针显微镜(SPM)使人们不仅可以观察到物质表面的微观形貌,还可以在微纳米尺度上对样品表面进行加工,这种方法有可能成为未来微纳米器件的主要制作方法,成为推动人类科学和技术发展的新动力。主要介绍基于SPM的三种纳米加工方法:单原子操纵法、阳极氧化法和机械刻蚀法。详细阐述了各自的原理、特点及发展状况,并指出阳极氧化法是目前最有可能应用在实际生产制造中的加工方法,而机械刻蚀法则不仅可以作为纳米加工的手段,还可以应用于纳米加工机理方面的研究。