Scanning Tip Research Articles

Enhancing Effective Scanning Techniques for Digital Impression in Neonates with Cleft Lip and/or Palate: A Laboratory Study Investigating the Impact of Different Scanners, Scanning Tip Sizes, and Strategies

Background/Objectives: Digital impressions are increasingly used to manage Cleft lip and/or palate (CL/P), potentially offering advantages over traditional methods. This laboratory investigation sought to evaluate the impact of scanning tip sizes, different scanners, and scanning strategies on intraoral scanning in neonates with CL/P. Methods: Ten soft acrylic models were used to simulate the oral anatomy of neonates with CL/P, evaluating parameters such as the ability of different scanning tips to capture alveolar cleft depth, scanning time, number of scan stops, and scan quality. The study utilised various scanning tips, including the Carestream normal tip, Carestream side tip, and Trios 4 scanner tip to assess the alveolar cleft depth measurements. The Trios 4, Carestream, and iTero scanners were evaluated for the time taken, number of scan stops during cleft-unobstructed scanning and cleft-obstructed scanning. The quality of all scanned images was analysed. Results: The findings showed comparable accuracy in capturing alveolar cleft depth with the three-scanning tip (p > 0.05). Scanning time and the number of scan stops did not significantly differ across the three scanners and various scanning strategies employed (p > 0.05). However, scanning with the cleft obstructed required less time and resulted in fewer scan stops compared to cleft -unobstructed scanning. Despite these results, all scanners failed to record the deepest part of the alveolar cleft, highlighting a limitation in current scanning technology for neonates with CL/P. Conclusions: The study recommends enhancing intraoral scanning in this population by adjusting tip size, improving clinician training, optimizing protocols, and conducting further research to improve techniques.

Effects of scanning tip and pattern on color selection

Effects of scanning tip and pattern on color selection

In-vivo evaluation of scan tip and pattern effects

In-vivo evaluation of scan tip and pattern effects

Directional picoantenna behavior of tunnel junctions formed by an atomic-scale surface defect.

Plasmonic nanoantennas have attracted much attention lately, among other reasons because of the directionality of light emitted by fluorophores coupled to their localized surface plasmon resonances. Plasmonic picocavities, i.e., cavities with mode volumes below 1 nm3, could act as enhanced antennas due to their extreme field confinement, but the directionality on their emission is difficult to control. In this work, we show that the plasmonic picocavity formed between the tip of a scanning tunneling microscope and a metal surface with a monoatomic step shows directional emission profiles and, thus, can be considered as a realization of a picoantenna. Electromagnetic calculations demonstrate that the observed directionality arises from the reshaping and tilting of the surface charges induced at the scanning tip due to the atomic step. Our results pave the way to exploiting picoantennas as an efficient way for the far-field probing and control of light-matter interactions below the nanoscale.

Imaging Nanomechanical Vibrations and Manipulating Parametric Mode Coupling via Scanning Microwave Microscopy.

In this study, we present a novel platform based on scanning microwave microscopy for manipulating and detecting tiny vibrations of nanoelectromechanical resonators using a single metallic tip. The tip is placed on the top of a grounded silicon nitride membrane, acting as a movable top gate of the coupled resonator. We demonstrate its ability to map mechanical modes and investigate mechanical damping effects in a capacitive coupling scheme, based on its spatial resolution. We also manipulate the energy transfer coherently between the mode of the scanning tip and the underlying silicon nitride membrane, via parametric coupling. Typical features of optomechanics, such as anti-damping and electromechanically induced transparency, have been observed. Since the microwave optomechanical technology is fully compatible with quantum electronics and very low temperature conditions, it should provide a powerful tool for studying phonon tunnelling between two spatially separated vibrating elements, which could potentially be applied to quantum sensing.

Complete Selective Switching of Ferroelastic Domain Stripes in Multiferroic Thin Films by Tip Scanning

AbstractBiFeO3 is a rare single‐phase multiferroic which shows coupled ferroelectricity, ferroelasticity and antiferromagnetism at room temperature. Many fantastic properties of BiFeO3 are regulated by its domain structure. While (001) rhombohedral BiFeO3 thin films can possibly develop up‐to eight degenerate states of two‐variant 71° ferroelastic domain stripes, complete selective control of all possible switching paths between these states has not yet been achieved. Here, combining phase field simulations and scanning probe microscopy experiments, we demonstrated such a complete selective control. The tip bias and the built‐in field were shown to affect the volume fraction of the 71°, 109° and 180° switched domains in rhombohedral BiFeO3 thin films under single‐point loading. Meanwhile, tip scanning further broke the symmetry of the nucleated domains, leading to different switched domain patterns. We then grew BiFeO3 thin films with a specific two‐variant 71° ferroelastic domain state and showed that such a state could be deterministically switched into the other seven two‐variant domain states by collaborative controlling tip scanning and tip bias in scanning probe microscopy experiments. These results should deepen our current understanding on the domain switching kinetics in BiFeO3 thin films and indicate they are promising platforms for developing configurable electronic and spintronic devices.

AFM-NSOM Nano-Polarimeter: Wide-ranging sensing device for synchronized scanning

This paper explores the use of an enhanced AFM-NSOM system tip as a nanoscale polarimeter. The tip consists of a tungsten-silicon conical photodetector modified with four differently-shaped subwavelength apertures, which enable the determination of incident light's four Stokes parameters and in turn its polarization state on the Poincaré sphere. The system is mounted on a standard Atomic Force Microscope (AFM) cantilever and can serve as a triple-mode scanning system, with complementary topography scanning, optical data analysis, and polarization state detection. The device was designed and simulated using the Comsol Multi-Physics software package, and initial steps toward fabrication were taken using the application of advanced nanotechnology tools to a commercial AFM probe. After a discussion of the advantages and drawbacks of drilled scanning tips vis-a-vis standard ones, the article presents the simulation and fabrication results of the nano-polarimeter tip.

Atom Filtering Algorithm and GPU-Accelerated Calculation of Simulation Atomic Force Microscopy Images

Simulation of atomic force microscopy (AFM) computationally emulates experimental scanning of a biomolecular structure to produce topographic images that can be correlated with measured images. Its application to the enormous amount of available high-resolution structures, as well as to molecular dynamics modelling data, facilitates the quantitative interpretation of experimental observations by inferring atomistic information from resolution-limited measured topographies. The computation required to generate a simulated AFM image generally includes the calculation of contacts between the scanning tip and all atoms from the biomolecular structure. However, since only contacts with surface atoms are relevant, a filtering method shall highly improve the efficiency of simulated AFM computations. In this report, we address this issue and present an elegant solution based on graphics processing unit (GPU) computations that significantly accelerates the computation of simulated AFM images. This method not only allows for the visualization of biomolecular structures combined with ultra-fast synchronized calculation and graphical representation of corresponding simulated AFM images (live simulation AFM), but, as we demonstrate, it can also reduce the computational effort during the automatized fitting of atomistic structures into measured AFM topographies by orders of magnitude. Hence, the developed method will play an important role in post-experimental computational analysis involving simulated AFM, including expected applications in machine learning approaches. The implementation is realized in our BioAFMviewer software (ver. 3) package for simulated AFM of biomolecular structures and dynamics.

Three Sonographic Findings to Look for in Fibromatosis Colli: Scanning Tips and Report of Two Cases

Fibromatosis colli is a rare, benign mass of the sternocleidomastoid muscle (SCM), typically diagnosed in infants between weeks 1 to 8 of life. Physical examination of the infant will exhibit a firm lump on the affected side of the neck. The mass is typically unilateral and may be accompanied by torticollis. We present two cases of infants with fibromatosis colli. Sonographic examination is the preferred initial non-invasive diagnostic procedure, with 100% sensitivity. Ultrasound can confirm the diagnosis, avoiding unnecessary invasive interventions. Early diagnosis can prevent complications such as plagiocephaly, facial asymmetry, and scoliosis. We aim to provide the tools necessary to recognize fibromatosis colli by describing three key sonographic appearances. We will present two separate cases that demonstrate these findings and discuss how to sonographically rule out the many differential diagnoses.

Research on Tip Characterization Techniques Based on Two-Dimensional Self-Traceable Nano-Gratings

The characterization of scanning tip morphology is crucial for accurate linewidth measurements. Conventional rectangular characterizers are affected by lateral distortion caused by the nonlinearities in AFM scanning, leading to errors between the actual characterization results and the true values. In this study, we innovatively developed self-traceable two-dimensional nano-gratings using chromium atomic deposition technology and extreme ultraviolet interference lithography. We used this structure as a characterizer for conducting scanning tip characterizations.This paper analyzed the periodic stability of the grating sample during scanning and corrected the lateral distortion of atomic force microscopy (AFM) at scan scales of 0.5 µm and 1 µm based on its self-traceable characteristics. Additionally, we extracted the angle information of the scanning tip in the X direction and Y direction within a scan scale of 0.5 µm. The results demonstrate that the two-dimensional grating sample exhibited excellent periodic stability during scanning. The characterization errors for the tip’s X direction and Y direction angles are within ±2°, showing high consistency. This study highlights that self-traceable two-dimensional grating samples have the capability for in situ bidirectional characterization of tip information, providing a creative solution for the development of new-style tip characterizers.

Atomistic polarization model for Raman scattering simulations of large metal tips with atomic-scale protrusions at the tip apex.

Tip-enhanced Raman spectroscopy (TERS) has recently been developed to push the spatial resolution down to single-chemical-bond scale. The morphology of the scanning tip, especially the atomistic protrusion at the tip apex, plays an essential role in obtaining both high spatial resolution and large field enhancement at the Ångström level. Although it is very difficult to directly characterize the atomistic structures of the tip, the Raman scattering from the apex's own vibrations of the metal tip can provide valuable information about the stacking of atoms at the tip apex. However, conventional quantum chemistry packages can only simulate the Raman scattering of small metal clusters with few atoms due to huge computational cost, which is not enough since the shaft of the tip behind the apex also makes significant contributions to the polarizabilities of the whole tip. Here we propose an atomistic polarization model to simulate the Raman spectra of large metal tips at subwavelength scales based on the combination of the atomistic discrete dipole approximation model and the density functional theory. The atomistic tip with different sizes and stacking structures is considered in its entirety during the calculation of polarizabilities, and only the vibrational contributions from the tip apex are taken into account to simulate the Raman spectra of the tip. The Raman spectral features are found to be very sensitive to the local constituent element at the tip apex, atomic stacking modes, and shape of the tip apex, which can thus be used as a fingerprint to identify different atomistic structures of the tip apex. Moreover, our approaches can be extended to the metal tips with sub-wavelength sizes, making it possible to consider both the large scale and the atomistic detail of the tip simultaneously. The method presented here can be used as a basic tool to simulate the Raman scattering process of the metal tips and other nanostructures in an economic way, which is beneficial for understanding the roles of atomistic structures in tip- and surface-enhanced spectroscopies.

(Invited) Multiphysics Model of the sSNOM Spectroscopy: Can Near-Field Probes Report the Spectrum of Nanomaterials?

Last decade has been celebrated with a substantial increase of publications on imaging of nanomaterials with near-field probes. The latter include Tip-Enhanced Raman and/or Photoluminescence Spectroscopy (TERS/TEPL), various near-infrared (NIR) Atomic Force Microscopy (AFM) based methods, and several scattering Scanning Near-field optical methods (sSNOM). Using various coherent sources, often tunable in terms of excitation, these methods produce high spatial resolution images – near-field scanning maps, in terms of a pixel size claimed to be limited only by the size of the scanning tip.By design, TERS/TEPL detects a spectral response at each point of a map, which is, naively speaking, gives us a local probe of optical material properties within a single pixel (at the fixed excitation wavelength). NIR-AFM and sSNOM (leaving aside the FTIR mode) allow to obtain quasi-spectral information by tweaking the excitation. In this case, the collected (elastic) signal is restricted to the wavelength of the excitation.The essence of the near-field method is in breaking the laws of a plane-wave reflection from the sample, which requires a sub-wavelength separation between the tip and the sample and a strong enough near-field coupling between those. Still, it is routinely assumed that the tip is an “ideal probe” and its role is to “channel” the information about the local optical response to the detector. Up to date, little is known about the spectral response of the tip-sample system from the perspective of quantum physics.In this work, several aspects of the problem: mechanical motion of the scanning tip, electrodynamics of the excitation/scattered light, and quantum solid state description of the sample and the tip – are combined to obtain, within a simple model, a full picture of the near-field detection. The results, though not general and limited by the simplicity of model used for the sake of clarity of derivation, shed the light on the spectral response of a typical near-field microscope and describe effects, earlier called “artifacts”, as natural response for coupled tip-sample elementary excitations. Lastly, an application of the model for an analysis of spectra of nBN heteronanotubes (Y. Feng, et.al, ACS Nano 15, 5600, 2021) will be presented. Acknowledgement: This work has been partially supported by NSF MRSEC (DMR-2011839).Fig. 1. (left) Amplitude and phase of the near-field optical signal vs. the optical frequency: S(ω). (right) Same optical amplitude and phase vs. ω and the phase of mechanical motion of an AFM tip. Figure 1

Morphology measurements by AFM tapping without causing surface damage: A phase shift characterization

The morphology measurement of a surface can be done by using an atomic force microscope (AFM). However, it is difficult to ensure that the measurement does not introduce any damage to the sample surface. This paper proposes that phase shift, the phase change between the original surface and scanned area, can provide a characteristic signal of the tip-surface interaction. On a poly (methyl methacrylate) thin film, the present investigation explored the relationship between phase shift and nondestructive surface morphology measurement under the tapping mode of an AFM. The study showed that when the drive amplitude was doubled, the phase shift reached from 0.47° to 1.85°. Under this condition, wrinkles became observable. With the tip radius in the range of 15–20 nm, no phase shift appeared between a scanned area and the original surface after multiple measurements. In this case, the tip-surface energy dissipation was in the range of 10–35 eV, showing a nondestructive interaction of the surface with the AFM tip. When the tip radius was about 55 nm, under the same tip excitation parameters, the energy dissipation per tap varied from 60 to 110 eV, and a phase shift occurred in the range of 0.02–0.64°, while the surface plastic deformation was still extremely minor after multiple tip scanning. A higher phase shift was occurred on the softer surface attributed to multiple scanning under tapping mode. The study found that the phase shift characteristics was a more sensible measure to signify the transition from a nondestructive to a destructive surface morphology measurement by using the tapping mode of an AFM.

Strong Piezoelectricity and Improved Rectifier Properties in Mono‐ and Multilayered CuInP2S6

AbstractMost atomically thin piezoelectrics suffer from weak piezoelectric response or current rectification along the thickness direction, which largely hinders their applications in a vertical crossbar architecture. Therefore, exploring new types of ultrathin materials with strong longitudinal piezoelectric coefficient and rectification is highly desired. In this study, the monolayer of van der Waals CuInP2S6 (CIPS) is successfully exfoliated and its strong piezoelectricity in the out‐of‐plane direction with an effective coefficient d33eff of ≈5.12 pm V−1, which is one or two orders of magnitude higher than that of most existing monolayer materials with intrinsic d33, is confirmed. A prototype vertical device is further constructed and the current rectification is achieved through the flexoelectricity induced by the scanning tip force. The switching between low and high rectification states can be readily controlled by tuning the mechanical loads. These findings manifest that CIPS possesses promising application in vertical nanoscale piezoelectric devices and provides a novel strategy for achieving a good current rectification in ultrathin piezoelectrics.

Microsphere‐Aided Super‐Resolution Scanning Spectral and Photocurrent Microscopy for Optoelectronic Devices

AbstractDielectric microspheres naturally possess unique optical properties by which the light's focus and confinement can be manipulated on a microscale. Combining microspheres and optical or Raman microscopy, super‐resolution imaging beyond the diffraction limit and enhancement of Raman signals are demonstrated to provide abundant spectroscopic information on materials. However, microsphere‐aided super‐resolution scanning photocurrent imaging remains challenging to date. Here, based on the photonic nanojet mechanism, a super‐resolution photocurrent and spectral microscopy equipped with a scanning tip with silica dielectric microspheres are presented. With such microsphere‐aided microscopy, order of magnitude enhancements for single‐point Raman and photoluminescence signals can be achieved, and the spatial resolutions for photocurrent and spectral mapping surpass the best resolution of the original confocal system restricted by the diffraction limit. This versatile system enables correlative super‐resolution spectral and photocurrent imaging, serving as a reliable tool for comprehensively understanding and uncovering the optoelectronic properties of materials.

Particle Smoother to Assimilate Asynchronous Movie Data of High-Speed AFM with MD Simulations.

High-speed (HS) atomic force microscopy (AFM) can be used to observe structural dynamics of biomolecules under near-physiological conditions. In the AFM measurement, the probe tip scans an area of interest and acquires height data pixel by pixel so that the obtained AFM image contains a measurement time difference. In this study, to integrate molecular dynamics simulations with asynchronous HS-AFM movie data, we developed a particle smoother (PS) method for Bayesian data assimilation, one of the machine learning approaches, by extending the previous particle filter method. With a twin experiment with an asynchronous pseudo HS-AFM movie of a nucleosome, we found that the PS method with the pixel-by-pixel data acquisition reproduced the dynamic behavior of a nucleosome better than the previous particle filter method that ignored the data asynchronicity. We examined several frequencies of particle resampling in the PS method, and found that resampling once per one frame was optimal for reproducing the dynamic behavior. Thus, we found that the PS method with an appropriate resampling frequency is a powerful method for estimating the dynamic behavior of a target molecule from HS-AFM data with low spatiotemporal resolution.

Mechanically Driven Reversible Polarization Switching in Imprinted BiFeO3 Thin Films

AbstractMechanically driven polarization switching via scanning probe microscopy provides a valuable voltage‐free strategy for designing ferroelectric nanodomain structures. However, it is still challenging to realize reversible polarization switching with mechanical forces. Here, the mechanically driven reversible polarization switching observed in imprinted ferroelectric BiFeO3 thin films is reported, i.e., up‐to‐down switching by a sharp scanning tip and down‐to‐up switching by a blunt tip. Free energy calculations, phase‐field simulations, and piezoresponse force microscopy reveal that reversible mechanical switching arises from the interplay among the flexoelectric effect, the piezoelectric effect, and the internal upward built‐in field in BiFeO3 films. This study gains a deeper insight into the mechanism and control of mechanically driven polarization switching, and provides guidance for exploring potential ferroelectric‐based electro‐mechanical microelectronics.

Novel type of whisker-tip cantilever based on GaN microrods for atomic force microscopy

High-resolution scanning probe microscopy (SPM) is a fundamental and efficient technology for surface characterization of modern materials at the subnanometre scale. The bottleneck of SPM is the probe and scanning tip. Materials with stable electrical, thermal, and mechanical properties for high-aspect-ratio (AR) tips are continuously being developed to improve their accuracy. Among these, GaN is emerging as a significant contender that serves as a replacement for standard Si probes. In this paper, for the first time, we present an approach that demonstrates the application of GaN microrods (MRs) as high-AR SPM probes. GaN MRs were grown using molecular beam epitaxy, transferred and mounted on a cantilever using focused electron beam-induced deposition and milled in a whisker tip using a focused ion beam in a scanning electron/ion microscope. The presence of a native oxide layer covering the GaN MR surface was confirmed by X-ray photoelectron spectroscopy. Current-voltage map measurements are also presented to indicate the elimination of the native oxide layer from the tip surface. The utility of the designed probes was tested using conductive atomic force microscopy and a 24-hour durability test in contact mode atomic force microscopy. Subsequently, the graphene stacks were imaged.

Facile Control of Ferroelastic Domain Patterns in Multiferroic Thin Films by a Scanning Tip Bias.

BiFeO3, known as the "holy grail of all multiferroics", provides an appealing platform for exploration of multifield coupling physics and design of functional devices. Many fantastic properties of BiFeO3 are regulated by its ferroelastic domain structure. However, a facile programable control on the ferroelastic domain structure in BiFeO3 remains challenging and our understanding on the existing control strategies is also far from complete. This work reports a facile control of ferroelastic domain patterns in BiFeO3 thin films under area scanning poling by exploiting the tip bias as the control parameter. Combining scanning probe microscopy experiments and simulations, we found that BiFeO3 thin films with pristine 71° rhombohedral-phase stripe domains exhibit at least four switching pathways solely by controlling the scanning tip bias. As a result, one can readily write mesoscopic topological defects into the films without the necessity to change the tip motion. The correlation between conductance of the scanned region and the switching pathway is further investigated. Our results extend the current understanding on the domain switching kinetics and the coupled electronic transport properties in BiFeO3 thin films. The facile voltage control of ferroelastic domains should facilitate the development of configurable electronic and spintronic devices.

Femtosecond Laser-Induced Periodic Surface Structures in Titanium-Doped Diamond-like Nanocomposite Films: Effects of the Beam Polarization Rotation.

We study the properties of laser-induced periodic surface structures (LIPSS) formed on titanium-doped diamond-like nanocomposite (DLN) a-C:H:Si:O films during ablation processing with linearly-polarized beams of a visible femtosecond laser (wavelength 515 nm, pulse duration 320 fs, pulse repetition rates 100 kHz-2 MHz, scanning beam velocity 0.05-1 m/s). The studies are focused on (i) laser ablation characteristics of Ti-DLN films at different pulse frequencies and constant fluence close to the ablation threshold, (ii) effects of the polarization angle rotation on the properties of low spatial frequency LIPSS (LSFL), and (iii) nanofriction properties of the 'rotating' LIPSS using atomic force microscopy (AFM) in a lateral force mode. It is found that (i) all LSFL are oriented perpendicular to the beam polarization direction, so being rotated with the beam polarization, and (ii) LSFL periods are gradually changed from 360 ± 5 nm for ripples parallel to the beam scanning direction to 420 ± 10 nm for ripples formed perpendicular to the beam scanning. The obtained results are discussed in the frame of the surface plasmon polaritons model of the LIPSS formation. Also, the findings of the nanoscale friction behavior, dependent on the LIPSS orientation relative to the AFM tip scanning direction, are presented and discussed.