Nanometer-scale Accuracy Research Articles

Tomography-based digital twin of Nd-Fe-B permanent magnets

Many functional materials have been designed at the multiscale level. To properly simulate their physical properties, large and sophisticated computer models that can replicate microstructural features with nanometer-scale accuracy are required. This is the case for permanent magnets, which exhibit a long-standing problem of a significant offset between the simulated and experimental coercivities. To overcome this problem and resolve the Brown paradox, we propose an approach to construct large-scale finite element models based on the tomographic data from scanning electron microscopy. Our approach reconstructs a polycrystalline microstructure with actual shape, size, and packing of the grains as well as the individual regions of thin intergranular phase separated by triple junctions. Such a micromagnetic model can reproduce the experimental coercivity of ultrafine-grained Nd-Fe-B magnets along with its mechanism according to the angular dependence of coercivity. Furthermore, a remarkable role of thin triple junctions as nucleation centers for magnetization reversal is revealed. The developed digital twins of Nd-Fe-B permanent magnets can assist their optimization toward the ultimate coercivity, while the proposed tomography-based approach can be applied to a wide range of polycrystalline materials.

Single site-controlled inverted pyramidal InGaAs QD–nanocavity operating at the onset of the strong coupling regime

Precise positioning of single site-controlled inverted pyramidal InGaAs quantum dots (QDs) at the antinode of a GaAs photonic crystal cavity with nanometer-scale accuracy holds unique advantages compared to self-assembled QDs and offers great promise for practical on-chip photonic quantum information processing. However, the strong coupling regime in this geometry has not yet been achieved due to the low cavity Q-factor based on the (111)B-oriented membrane structures. Here, we reveal the onset of phonon-mediated coherent exciton–photon interaction on our tailored single site-controlled InGaAs QD–photonic crystal cavity. Our results present the Rabi-like oscillation of luminescence intensity between excitonic and photonic components correlated with their energy splitting pronounced at small detuning. Such Rabi-like oscillation is well reproduced by modeling the coherent exchange of the exciton-photon population. The modeling further reveals an oscillatory two-time covariance at QD-cavity resonance, which indicates that the system operates at the onset of the strong coupling regime. Moreover, by using the cavity mode as a probe of the virtual state of the QD induced by phonon scattering, it reveals an increase in phonon scattering rates near the QD–cavity resonance and asymmetric phonon emission and absorption rate of even around 50 K.

DNA origami-mediated plasmonic dimer nanoantenna-based SERS biosensor for ultrasensitive determination of trace diethylstilbestrol

Diethylstilbestrol (DES) is a threatening factor to the human endocrine system. Here, we reported a DNA origami-assembled plasmonic dimer nanoantenna-based surface-enhanced Raman scattering (SERS) biosensor for measuring trace DES in foods. A critical factor influencing the SERS effect is interparticle gap modulation of SERS hotspots with nanometer-scale accuracy. DNA origami technology aims to generate naturally perfect structures with nano-scale precision. Exploiting the specificity of base-pairing and spatial addressability of DNA origami to form plasmonic dimer nanoantenna, the designed SERS biosensor generated electromagnetic-enhancement and uniform-enhancement hotspots to improve sensitivity and uniformity. Owing to their high target-binding affinity, aptamer-functionalized DNA origami biosensors transduced the target recognition into dynamic structural transformations of plasmonic nanoantennas, which were further converted to amplified Raman outputs. A broad linear range from 10−10 to 10−5 M was obtained with the detection limit of 0.217 nM. Our findings demonstrate the utility of aptamer-integrated DNA origami-based biosensors as a promising approach for trace analysis of environmental hazards.

Exciton-polariton dynamics of the single site-controlled quantum dot-nanocavity in the coexisting strong-weak coupling regime

Deterministic positioning single site-controlled high symmetric InGaAs quantum dots (QDs) in (111)B-oriented GaAs photonic crystal cavities with nanometer-scale accuracy provides an idea component for building integrated quantum photonic circuits. However, it has been a long-standing challenge of improving cavity Q-factors in such systems. Here, by optimizing the trade-off between the cavity loss and QD spectral quality, we demonstrate our site-controlled QD-nanocavity system operating in the intermediate coupling regime mediated by phonon scattering, with the dynamic coexistence of strong and weak coupling. The cavity-exciton detuning-dependent micro-photoluminescence spectrum reveals concurrence of a trend of exciton-polariton mode avoided crossing, as a signature of Rabi doublet of the strongly coupled system. Meanwhile, a trend of keeping constant or slight blue shift of coupled exciton–cavity mode(CM) energy across zero-detuning is ascribed to the formation of collective states mediated by phonon-assisted coupling, and their rare partial out-of-synchronization linewidth-narrowing is linked to their coexisting strong-weak coupling regime. We further reveal the pump power-dependent anti-bunching photon statistical dynamics of this coexisting strong-weak coupled system and the optical features of strongly confined exciton-polaritons, and dark-exciton-like states. These observations demonstrate the potential capabilities of site-controlled QD-cavity systems as deterministic quantum nodes for on-chip quantum information processing and provide guidelines for future device optimization for achieving the strong coupling regime.

High-throughput deterministic plasma etching using array-type plasma generator system.

A deterministic processing method is a high-precision finishing method, where the to-be-removed amount of material at each pointof the work surface is calculated based on an accurately measured present surface shape and is removed precisely using a numerically controlled (NC) processing system. Although this method has achieved nanometer-scale accuracy, the method requires considerable time to scan the work surface, leading to low productivity. Therefore, using an individual on-off controllable array-type plasma generator covering the entire work surface, enabling simultaneous NC plasma processing is proposed herein. A novel intermittent gas flow system was constructed using cyclic on-off control of the gas supply and exhaust valves instead of the commonly used continuous gas flow to achieve uniform in-plane plasma etching. It was found that uniform removal could be achieved by combining it with a pulse-modulated high-frequency power supply and setting the plasma generation time in one cycle to be sufficiently short. Furthermore, a power control approach was developed for maintaining a constant plasma state, even while varying the plasma-generating array elements, which resulted in a demonstration experiment of NC plasma etching that successfully reduced the thickness variation of a silicon substrate.

Analysis and design of fringe phase control system for scanning beam interference lithography

Scanning beam interference lithography (SBIL) is an advanced technology developed for manufacturing large-area diffraction grating at a nanometer-scale phase accuracy. To withstand environmental disturbances and maintain the interference fringes still relative to the substrate, SBIL requires high-precision phase control. We proposed a fringe phase control system with homodyne detection for SBIL. First, a homodyne detector is employed to achieve high-precision phase measurement, while ensuring the simplicity of the optics and high laser utilization. The time-varying nonlinear error in the measurement results is corrected by a dynamic ellipse fitting method. To reduce the latency effect, a lead controller is designed using the root locus method based on the model identification result. The lead controller considerably increases the control bandwidth while ensuring a sufficient phase margin, which further suppresses disturbances and stabilizes the interference fringes to within ∼1 / 60 of the fringe period. Wide-range phase tracking for perpendicular scanning with high accuracy is also verified through an experiment.

A 3-DOF piezoelectric driven nanopositioner: Design, control and experiment

In this paper, a novel 3-degree-of-freedom (DOF) nanopositioner was investigated in order to position objects with nanometer scale accuracy. Nanopositioners are used in a variety of real-world applications, e.g. biomedical technology and nanoassembly. In this work, a nanopositioner was firstly designed with the flexure diaphragm guider, capacitive sensors and walking piezoelectric actuators. The specifically designed monolithic flexure diaphragm guider was able to significantly restrict motions in the other unwanted directions. The walking piezoelectric actuator can enable the developed nanopositioner to have nanometer scale positioning accuracy and a large travel range. Then a closed-loop sliding mode control strategy was developed to overcome the effect of the actuator’s speed nonlinearity and its stability was analysed based on Lyapunov theory. Finally, experiments focused on coupling displacement and point-to-point movement were conducted. The observed results revealed that the ratio of coupling displacement to Z displacement was less than 0.1%, which means that the coupling displacement was less than 120 nm during the Z direction travel range of the nanopositioner from −80 μm to 80 μm. Moreover, the positioning accuracy in the Z direction of point-to-point movement was within 10 nm and the dynamic response settled within 0.2 s. Therefore, the experimental results showed that the novel piezoelectric driven nanopositioner has excellent performance in terms of coupling displacement and nanometer scale accuracy for point-to-point movement.

A Differential Measurement System for Surface Topography Based on a Modular Design

In this paper, a novel design of a surface topography measurement system is proposed, to address the challenge of accurate measurement in a relatively large area. This system was able to achieve nanometer-scale accuracy in a measurement range of 100 mm × 100 mm. The high accuracy in a relatively large area was achieved by implementing two concepts: (1) A static coordinate system was configured to minimize the Abbe errors. (2) A differential measurement configuration was developed by setting up a confocal sensor and a film interferometry module to separate the motion error. In order to accommodate the differential measurement probes from both sides of the central stage and ensure the system rigidity with balanced supports, separate linear guides were introduced in this system. Therefore, the motion Degree of Freedom (DoF) was analyzed in order to address the challenge of an over-constrained mechanism due to multiple kinematic pairs. An optimal configuration and a quick assembly process were proposed accordingly. The experimental results presented in this paper showed that the proposed modular measurement system was able to achieve 10 nm accuracy in measuring the surface roughness and 100 nm accuracy in measuring the step height in the range of 100 mm × 100 mm. In summary, the novel concept of this study is the build of a high-accuracy system with conventional mechanical components.

Dual-Sensing System for Monitoring Ion Concentration Change in Electrochemical Micro Machining

Currently, no reliable electrolyte concentration monitoring method exists for ultra-short pulsed electrochemical micromachining. A dual-sensing system for electrolyte concentration monitoring is proposed in this work. An inductance element is added into the classical pulsed electrochemical micromachining circuit system. For it, a modified circuit equation is proposed by which the coupled electronic and ion circuit is analyzed, and two modes of the coupled circuit are found. The asynchronous mode is used to monitor the concentration changes of the ions in electromechanical micromachining, and a novel method of electrolyte concentration monitoring is obtained. Combining this method with the short-circuit frequency monitoring method, an electrolyte concentration monitoring method based on the dual-sensing monitoring system is proposed, and corresponding monitoring software is produced. The software is used in actual microstructure processing experiments, obtaining nanometer-scale machining accuracy.

Ultrahigh-Precision Rotational Positioning Under a Microscope: Nanorobotic System, Modeling, Control, and Applications

High-precision positioning is an essential requirement for sample operation at a small scale. At the current stage, although nanometer-scale accuracy has been achieved for the linear positioning, the rotational positioning (attitude control) is still very challenging and rarely addressed. This paper presents a rotatable nanorobotic system with rotational degrees of freedom first. Then, the system error, i.e., nonaxisymmetrical eccentricity error of the mechanism, is investigated dynamically and its fault model is established. After that, a double-loop servo repetitive controller is accordingly designed based on the circle interpolation strategy. The theoretical analysis and experimental results verify that the rotational positioning accuracy can be controlled up to submicrometers stably, which improves at least one order of magnitude than the current static method. Finally, two application cases are given to highlight the significance of this approach, i.e., surface defect detection from $\text{360}^{\circ }$ and in situ twisting characterization of 1-D micro/nanomaterial. This research paves a new avenue for the ultrahigh rotational positioning at microscopy environment, which is expected to generate a long-term impact on the micro/nanofields, such as microscopy imaging, material characterization, and so on.

Focussed Ion Beam

SummaryFocussed Ion Beam ‐“Cutting Edge” Technology of Material AnalysisWith the focussed ion beam technique it is possible to sputter almost any material with nanometer scale accuracy and directly image or chemically analyze structures below the surface. The major advantage towards conventional cross‐section polishing is the high precision which allows to investigate even the smallest local defects. Applications of the focused ion beam even extend to the generation of complex nano structures. This article describes the operational modes, limits and constraints of the method and gives application examples from the field of material analytics.

Control of the interaction strength of photonic molecules by nanometer precise 3D fabrication

Applications for high resolution 3D profiles, so-called grayscale lithography, exist in diverse fields such as optics, nanofluidics and tribology. All of them require the fabrication of patterns with reliable absolute patterning depth independent of the substrate location and target materials. Here we present a complete patterning and pattern-transfer solution based on thermal scanning probe lithography (t-SPL) and dry etching. We demonstrate the fabrication of 3D profiles in silicon and silicon oxide with nanometer scale accuracy of absolute depth levels. An accuracy of less than 1nm standard deviation in t-SPL is achieved by providing an accurate physical model of the writing process to a model-based implementation of a closed-loop lithography process. For transfering the pattern to a target substrate we optimized the etch process and demonstrate linear amplification of grayscale patterns into silicon and silicon oxide with amplification ratios of ∼6 and ∼1, respectively. The performance of the entire process is demonstrated by manufacturing photonic molecules of desired interaction strength. Excellent agreement of fabricated and simulated structures has been achieved.

Large area nanoimprint enables ultra-precise x-ray diffraction gratings.

A process for fabrication of ultra-precise diffraction gratings for high resolution x-ray spectroscopy was developed. A grating pattern with constant or variable line spacing (VLS) is recorded on a quartz plate by use of e-beam lithography with nanometer scale accuracy of the groove placement. The pattern is transferred to a massive grating blank by large area nanoimprint followed by dry or/and wet etching for groove shaping. High fidelity of the nanoimprint transfer step was confirmed by differential wavefront measurements. Successful implementation of the suggested fabrication approach was demonstrated by fabrication of a lamellar 900 lines/mm VLS grating for a soft x-ray fluorescence spectrometer.

Features of Capacitive Displacement Sensing That Provide High-Accuracy Measurements with Reduced Manufacturing Precision

The capacitive displacement sensing method based on time grating employs a set of movable induction electrodes suspended with some gap width above a set of fixed excitation electrodes, and signals are obtained through electric field coupling. In this paper, we consider three features of time-grating capacitive displacement sensors that reduce the required manufacturing precision while maintaining high-accuracy measurements. First, the effect of edge roughness of the induction electrodes is suppressed by the filtering effect of the overlapping area integral method. Second, the effect of edge roughness of the excitation electrodes can be suppressed by the smoothing effect of the electric field. Third, the averaging effect of multiple induction electrodes is adopted to reduce the effect of geometric errors in the excitation electrodes. Printed circuit board manufacturing technology with a manufacturing accuracy on the order of 10 μ m is selected to fabricate a prototype time-grating capacitive sensor, and a linearity of 0.005% is obtained for a single-period range of 0.8 mm. The measurement accuracy is largely independent of the manufacturing precision owing to the three aforementioned smoothing effects, which is promising for transforming the presently challenging technology of long-range displacement measurements with nanometer-scale accuracy into a conventional technology.

Nanometer-scale accuracy electrochemical micromachining with adjustable inductance

Electrochemical micromachining technique using ultra short pulses can increase machining resolution. However, the pulse duration is the only effective control parameter of the machining resolution. Here, we propose a controlled electrochemical micromachining technique. We added an adjustable inductance element in the equivalent circuit of the electrochemical micromachining to form a coupled fluid-electric circuit. The machining resolution depends on both local separation between the electrodes and the adjustable inductance. So, the adjustable inductance can be taken as another effective control parameter of the machining resolution. As the inductance increases, the large polarization voltage can be more easily confined to the electrode regions in very close proximity. This technique was used for machining some micro structures, and a nanometer scale machining resolution was achieved easily when an ordinary pulse source is used.

Depth-Resolved X-ray Absorption Spectroscopy by Means of Grazing Emission X-ray Fluorescence.

Grazing emission X-ray fluorescence (GEXRF) is well suited for nondestructive elemental-sensitive depth-profiling measurements on samples with nanometer-sized features. By varying the grazing emission angle under which the X-ray fluorescence signal is detected, the probed depth range can be tuned from a few to several hundred nanometers. The dependence of the XRF intensity on the grazing emission angle can be assessed in a sequence of measurements or in a scanning-free approach using a position-sensitive area detector. Hereafter, we will show that the combination of scanning-free GEXRF and fluorescence detected X-ray absorption spectroscopy (XAS) allows for depth-resolved chemical speciation measurements with nanometer-scale accuracy. While the conventional grazing emission geometry is advantageous to minimize self-absorption effects, the use of a scanning-free setup makes the sequential scanning of the grazing emission angles obsolete and paves the way toward time-resolved depth-sensitive XAS measurements. The presented experimental approach was applied to study the surface oxidation of an Fe layer on the top of bulk Si and of a Ge bulk sample. Thanks to the penetrating properties and the insensitivity toward the electric conduction properties of the incident and emitted X-rays, the presented experimental approach is well suited for in situ sample surface studies in the nanometer regime.

Microcantilever based distance control between a probe and a surface.

We demonstrate a method to control the distance between a custom probe and a sample on a μm to nm scale. The method relies on the closed-loop feedback on the angular deflection of an in-contact AFM microcantilever. High performance in stability and accuracy is achieved in this method by taking advantage of the small mechanical feedback path between surface and probe. We describe how internal error sources that find their origin in the microcantilever and feedback can be minimized to achieve an accurate and precise control up to 3 nm. In particular, we investigated how hysteresis effects in the feedback caused by friction forces between tip and substrate can be minimized. By applying a short calibration procedure, distance control from contact to several micrometers probe-sample distance can be obtained with an absolute nanometer-scale accuracy. The method presented is compatible with any probe that can be fixed on a microcantilever chip and can be easily built into existing AFM systems.

Accurate High Throughput Bright Field Bead Tracking using Gpu Hardware

With the recent advances in camera technology, the potential of microscopy to study the behaviour of single molecules can make great strides. Here, we present a highly-optimized method to track magnetic beads in a bright-field microscopy setup that takes full advantage of both new camera technology and fast graphics hardware to do parallel computations. Using large field-of-view cameras, we can carry out real-time tracking of hundreds of magnetic beads in parallel while maintaining nanometer-scale accuracy. Additionally, we can use fast CMOS camera's to perform real-time bead tracking at an acquisition rate of several kHz. These advances allow us to use the magnetic tweezer as a tool to acquire detailed statistical knowledge at high temporal resolution of the behaviour of single molecules or molecular complexes.

Scanning-free grazing emission x-ray fluorescence by means of an angular dispersive arrangement with a two-dimensional position-sensitive area detector

We report on the application of a two-dimensional position-sensitive area detector towards grazing emission x-ray fluorescence (GEXRF) spectroscopy. GEXRF allows for surface-sensitive studies with nanometer-scale accuracy in the depth direction by measuring the intensity variation of an x-ray fluorescence line with the grazing emission angle. The presented experimental setup is based on a fixed sample-detector arrangement and does not require any moving components. We show that the dispersion of the grazing emission angle along a position-sensitive detector allows to acquire with an excellent angular resolution a full GEXRF profile in a single measurement. Moreover, the use of a two-dimensional detector allows to perform experiments with an increased solid angle of detection per emission angle. This results in combination with the nonsequential and simultaneous acquisition of the GEXRF profiles of different emission lines in considerably reduced acquisition times. The realization, the demands, and the main characteristics of the scanning-free GEXRF setup will be presented. A few experimental examples will serve to illustrate the analytical possibilities offered by the presented setup.

Three-dimensional nanostructures by focused ion beam techniques: Fabrication and characterization

Abstract