Probe Tips Functionalized with Colloidal Nanocrystal Tetrapods for High‐Resolution Atomic Force Microscopy Imaging

We fabricated a polymer-metal combined atomic force microscopy (AFM) probe by two steps; a polymeric resin was used at first step, and a metal-ion was used at second step which needs more fabricating time than the resin. At first step, we fabricated a cylindrical base on to a commercial cantilever. At second step, we fabricated a conical probe on to the fabricated cylindrical base. To make the conical probe composed with silver, a 0.2 M aqueous solution of silver nitrate (AgNO3) was used. A 50 microm length polymeric-metallic hybrid tip has been fabricated to observe large bio and food samples. Generally, the AFM images of bio/food samples show cliff-like sharp patters in vertical. However, the AFM image by fabricated long tip shows clear structure of each brown rice flours. As most of commercial tips have three-angular pyramidal, the scanned results should be influenced by the lateral face of the three-angular pyramid, which results in cliff-like images. Because the sample size is large, the side area of the sample was adversely affected by the pyramidal structure during imaging. This problem may be resolved by designing conical structure tips. As the conical structure has no edge, the AFM image becomes clear. The fabricated tip has conical structure, and a clear AFM image was achieved.

This article provides data on the scanning tunnelling microscopy (STM), atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM) images of InAs(001) surface. Using the frequency-modulation (FM) method in AFM and KPFM, atomic resolution topography and contact potential difference (CPD) images of InAs(001) surface were obtained. The InAs(001) surface reconstruction images observed by STM and AFM are compared. The effect of AFM tip condition and tip-sample distance to AFM and KPFM imaging is verified by measuring frequency shift vs. tip-sample distance spectroscopy. This data article is related to the article entitled, “Kelvin prove force microscopy and its application” (Melitz et al., 2011) [1].

In this thesis, two inversion-based feedforward control approaches have been developed and implemented to high-speed large-range atomic force microscope (AFM) imaging and nanofabrication, respectively. High-speed large-range AFM imaging and nanofabrication are needed in many areas and have attracted great interests. Challenges, however, must be overcome because in high-speed largerange AFM operation, large positioning error of the AFM probe relative to the sample can be generated due to the adverse effects of the hardware. The nonlinear hysteresis and the vibrational dynamics effects of the piezotube actuator must be addressed during the high-speed lateral scanning of the AFM imaging over large imaging size. In addition, precision positioning of the AFM probe in the vertical direction is even more challenging (than the lateral scanning) because the desired trajectory (i.e., the sample topography profile) is unknown in general, and the probe positioning is also effected by and sensitive to the probe-sample interaction. Finally, in AFM multi-axis nanofabrication, additional positioning errors are induced by the large cross-axis dynamics coupling effect. The large positioning errors generated during high-speed, large-range fabrication will lead to large defects in the fabricated structures or devices. In the thesis, firstly, to compensate for the adverse effects generated during high-speed large-range AFM imaging, an integrated approach is proposed, which combines the enhanced inversion-based iterative control technique (EIIC) for lateral x-y axis scanning with a dual-stage piezoactuator for the vertical z-axis positioning. The main contribution of this integrated approach is the combination of an advanced control algorithm with an advanced hardware platform. This approach is demonstrated in experiments by imaging a large-size (50 μm) calibration sample at high speed (50 Hz scan rate). Then secondly, to achieve high-speed large-range multi-axis AFM nanofabrication, a recently developed model-less inversion-based iterative control technique (MIIC) is utilized to overcome the adverse effects involved in high-speed large-range multi-axis AFM nanofabrication. By using this advanced control technique,

We present a fast method for computing simulated Atomic Force Microscope (AFM) image scans (including tip artifacts). The basic insight is that the array of depth values in the depth buffer of a graphics system is analogous to the height field making up an AFM image, and thus the ability of graphics hardware to compute the depth of many pixels in parallel can be used to radically speed up the AFM imaging simulation. We also present a method for reconstructing better approximations to the true shape from AFM images distorted by tip artifacts. These algorithms are implemented using operations from 3D grayscale mathematical morphology operations of dilation and erosion.

One of the pleasures of teaching introductory biology courses is learning new things about old, familiar subjects … such as the differences between eukaryotes and prokaryotes. For a eukaryotic cell biologist, such learning usually entails examining how bacteria function, in ways other than how they replicate and transcribe DNA and how they synthesize protein. I find it interesting, for example, to understand how bacteria maintain their distinctive spherical, rod-like or spiral shapes; or how they make an external cell wall, if they have one; or how they segregate the products of DNA replication faithfully into daughter cells. New answers to these questions are especially interesting because, in my mistaken eukaryote-centric view, bacteria lack cytoskeletons and cytoskeletal proteins, which might be involved in maintaining cell shape, regulating cell wall synthesis, and erecting something like a mitotic apparatus. Which brings me to a second and equally delightful pleasure derived from teaching introductory biology: debunking worn-out notions. Bacteria do possess cytoskeletons made of proteins which resemble the actin and tubulin familiar to eukaryotic cell biologists. Here I review several, recently published videos that characterize the in vitro behaviors of the actin-like protein, ParM (also known as StbA), and the tubulin-like protein, FtsZ and its in situ localization during cell division. For sake of completeness, I also briefly mention some recent work on the protein crescentin (CreS), an intermediate filament-like molecule, in the absence of published videos. By way of background material, readers may find the recent review by Michie and Lowe (2006) on the dynamics of bacterial cytoskeletal proteins helpful, including the authors' provocative list of “Future Issues to be Resolved.” Also, students and their teachers may wish to compare the videos reviewed below with those involving tubulin and actin (Watters, 2002 , 2004 , 2005 ), which could generate some interesting discussions about the differences and similarities of prokaryotes and eukaryotes. In such discussions, for example, students may raise questions concerning the evolution of “the cytoskeleton”; in which case, they may also find an earlier review on the subject (van den Ent et al., 2001 ) and commentary (Erickson, 2001 ) very helpful, for both an overview and a relevant bibliography. Students and their teachers will also want to discuss critically whether the similarities exhibited by the bacterial and eukaryotic cytoskeletal proteins reflect phylogenetic homologies or, rather, represent good examples of convergent evolution. At this point, readers more familiar with eukaryotic cell biology should be advised the videos being reviewed (as well as the review figures below) were, with one exception, obtained using 100× objectives: that is, at the limits of light microscopy resolution. Thus, the fields of view are small and the images do not seem as large or as sharp as seen in lower-magnification images of eukaryotic cells. Moreover, all but one of the video images were obtained by fluorescence microscopy at low light intensities, which required longer time exposures and time-lapse digital imaging (with accompanying loss of intervening visual detail). In contrast, the set of images portraying FtsZ behavior in vitro was obtained using an atomic force microscope (AFM), which is not a microscope in the usual sense of the term. An AFM lacks lenses and forms an image by means of a probe that traverses the object in a systematic manner, one line at a time. The image formed by the kind of AFM most commonly used for molecular studies is topographical in nature, and image details receive contrast from their size (changes in the z-axis). These images are created in a raster-like manner by the movement of a very fine, whisker-like projection across the surface of an object. AFM resolution, consequently, reflects the size of the probe tip, relative to the detail being probed, and not the diffraction of electromagnetic or electron radiation as seen in more familiar micrographs. With a very small tip, spatial resolution in an AFM image can be very high. Temporal resolution, however, is limited, because of the time usually required to achieve raster-like movements across the field. More information about AFM may be obtained at http://stm2.nrl.navy.mil/how-afm/how-afm.html#General%20concept.

Nanotubes, particularly single-walled carbon nanotubes (SWCNTs), represent an important class of materials with valuable electrical, mechanical, and thermal properties. However, accurate characterization of nanotube network morphologies remains a significant challenge. We present a deep learning-based approach for extracting nanotube morphologies from atomic force microscopy (AFM) images utilizing an image-to-image (I2I) translation framework based on cycleGAN with a specialized loss function that learns to transform AFM images containing nanotubes to images of pure substrates. By subtracting these translated substrate images from the original AFM images, we effectively isolated nanotube morphologies even on substrates with roughness exceeding the nanotube diameter. We validate our approach through physics-based simulation studies and application to roll-to-roll printed carbon nanotube transistors on flexible polymeric substrates.Our method outperforms tranditional image processing and supervised learning models in sensitivity and accuracy for CNT network extraction. This improved characterization capability provides useful insights for optimizing the fabrication processes of CNT-TFTs, supporting their development for flexible electronic applications. The methodology extendsbeyond carbon nanotubes to other nanomaterial-based electronic devices, with future work aimed at expanding the model's generalization and integrating with real-time AFM imaging.

Ab initio periodic Hartree-Fock calculations with the full potential and minimum basis set are applied to interpretation of scanning tunneling microscope (STM) and atomic force microscope (AFM) images on 1TVTe2. Our results show that the simulated STM image shows asymmetry while the simulated AFM image shows the circular electron densities at the bright spots without asymmetry of electron density to agree with the experimental AFM image. The bright spots of both the STM and AFM images of VTe2 are associated with the surface Te atoms, while the patterns of bright spots of STM and AFM images are different.

The importance of the atomic force microscope (AFM), in nano-technology, demands understanding of factors affecting AFM performance and image quality. Through a simulation study, the impact of scanning parameters on AFM images acquired in contact-mode has been investigated. The performance and limitations of commercial AFM controllers was also discussed. Based on the generated images, it is seen that high speed scans may require a large force set-point to maintain probe-sample contact at the expense of higher surface deformation, contact area, and friction force. Hence, reducing resolution and increasing image distortion. The sensitivity of AFM images to scan and controller parameters, invites the development of a systematic procedure for parameter selection for a given sample and operating environment. This would greatly reduce the current guess work in parameter selection and improve image repeatability. Currently, commercial control systems do limit the capabilities of the AFM in terms of speed and data repeatability. A good controller should be able to compensate for the large uncertainty due to different cantilevers and samples that may be used, nonlinearities, and system resonances. In addition, it should provide a tight tolerance on sample surface tracking both during transient and at steady state operation. This would enable robust high-speed operation and allow small or negative force set-point to be used.

Protein-DNA interactions are pivotal for many essential biological processes. Atomic force microscopy (AFM) imaging of protein-DNA systems involved in DNA target site search, identification, and processing by proteins has contributed invaluable information to our understanding of the underlying mechanisms. The single molecule 3D resolution of AFM enables us to uncover stoichiometries and conformational properties of protein-DNA complexes. Its molecular resolution places AFM at the interface between the atomic resolution achievable by crystallography and the comparably poor (typically > hundred nanometers) spatial resolution of optical microscopy. Furthermore, the transient character of protein interactions with nonspecific DNA sites, for example during their target site search renders these complexes difficult to resolve by standard ensemble methods. Here, we review current applications and capabilities of as well as novel advances in AFM imaging in protein-DNA interaction studies.

We describe in detail how atomic force microscopy (AFM) images can be routinely achieved with macroscopic silicon-based chips integrating mesoscopic tips, paving the way for the development of new near field devices combining AFM imaging with any kind of functionality integrated on a chip. The chips have been glued at the end of the free prong of 100 kHz quartz tuning forks mounted in Qplus configuration. Numerical simulations by modal analysis have been carried out to clarify the nature of the vibration modes observed in the experimental spectra. It is shown that two low frequency modes can be used to drive the system and scan the surface with a great stability in amplitude modulation as well as in frequency modulation AFM under ultrahigh vacuum. The AFM capabilities are demonstrated through a series of examples including phase and dissipation contrast imaging, force spectroscopy measurements, and investigations of soft samples in weak interaction with the substrate. The lateral resolution with the tips grown by focused ion beam deposition already matches the one achieved in standard amplitude modulation mode AFM experiments.

Scanning electron microscopy (SEM) and ion beam milling (FIB) techniques are mature nanoscale measurement technologies, while Atomic Force Microscopy (AFM) is a developing technology with intense interest in the scientific community for basic research and development. We discuss the recent integration of these techniques into a single instrument enabled by technological innovation in AFM instrument design, and applications of this instrument for characterization of FIB milled trenches. An AFM integrated into the SEM/FIB has specific design constraints that need to be met involving the AFM scanner, probe design, and feedback loop so that it geometrically fits into the chamber without interfering with the electron and ion beams. An ultraflat scanning stage was thus developed for precise sample motion that enable large ranges (85 microns or greater) in x,y, z. SPM probes that do not interfere with the electron beam were manufactured from fused silica in a cantilevered geometry (see Fig 1) where there is full visualization of the tip, without any loss of SPM functionality. These probes are combined with a tuning fork based feedback mechanism to maintain accurate tip-sample control; this mechanism does not involve lasers or optical beam deflection that interferes with the electron and ion beams. The many benefits of this combined approach to three-dimensional nanoscale characterization are illustrated in the imaging of a FIB milled trench. Figure 2a shows an AFM image profiling a 25-µm-deep trench milled in silicon with FIB imaged with the large Z range of the system. In this measurement, the FIB beam was used to mill this feature, and it was followed immediately by AFM imaging without having to remove the specimen from the FIB chamber and search in the AFM. Furthermore, the true depth of the trench was measured by the AFM in a crosssectional profile (Figure 2b) while a 3D reconstruction revealed the geometry of the sidewall (Figure 2c). Sidewall imaging with such long and exposed tips now are feasible with this instrument. The red arrow in this image clearly shows a Pt decoration on this structure, and the white arrow shows an undercut. Additionally, the ability of AFM to quickly and easily follow FIB milling with high Z resolution provides a straightforward and convenient method to check on FIB milling results. This capability is demonstrated in Figure 3 where several FIB-milled features in Si were monitored during the milling process. The grayscale SEM image in Figure 3a can easily locate these features and measure their widths but cannot provide direct information on their depths. The AFM delivers a 3D reconstruction (Figure 3b), and a cross sectional profile that together provide a true topographic map of specimen features. These depth profiles demonstrate the linearity of the etching process with time. This instrument incorporates important innovations in the design and technology of atomic force microscopy enabling its integration with SEM and FIB into a single powerful capability.

Quantitative determination of isomorphous substitutions on clay mineral surfaces through AFM imaging: A case of mica

Atomic force microscope (AFM) probes and AFM imaging by extension are the product of exceptionally refined silicon micromachining, but are also restricted by the limitations of these fabrication techniques. Here, the nanoscale additive manufacturing technique direct laser writing is explored as a method to print monolithic cantilevered probes for AFM. Not only are 3D printed probes found to function effectively for AFM, but they also confer several advantages, most notably the ability to image in intermittent contact mode with a bandwidth approximately ten times larger than analogous silicon probes. In addition, the arbitrary structural control afforded by 3D printing is found to enable programming the modal structure of the probe, a capability that can be useful in the context of resonantly amplifying nonlinear tip-sample interactions. Collectively, these results show that 3D printed probes complement those produced using conventional silicon micromachining and open the door to new imaging techniques.

Reconstruction of atomic force microscopy image using compressed sensing

Electrochemical scanning tunneling microscopy (ESTM) and atomic force microscopy (AFM) images of hydrogen-terminated Si(111) in several solutions have been studied to evaluate the performance of the AFM method. In dilute H2SO4 solution, the overall features of AFM images were similar to those of ESTM images, suggesting that both images reflect the topography of the bare H-Si(111) surface. However, AFM images in ultrapure water and in dilute NaOH solution were successfully obtained, while ESTM images were not. These results indicate that AFM is a powerful method for studying topographic change of Si in solutions during the wet cleaning process.