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The controlled rotation of individual cells plays a crucial role in enabling three-dimensional multi-angle observation of cellular structure, function, and dynamic processes. Reported cell rotation techniques often struggle to strike a balance between high precision and simple control, and they exhibit limited control flexibility, typically achieving only uniaxial cell rotation. In this study, we propose a cell rotation technique in three dimensions based on optofluidics, which utilizes optical tweezers to immobilize the cell and exploits the asymmetry of the surrounding flow to drive cell rotation. By adjusting the focal position of the optical tweezers, cells can be positioned within various flow profiles, enabling control of the rotation speed, rotation direction, and rotation axis of cells. This approach simplifies the manipulation procedure, achieving desirable control precision and greater rotation flexibility. Using our approach, multi-angle surface imaging projections of target cells can be rapidly obtained, followed by capturing the cell contour data from the images. By combining the cell contour data with corresponding angular position information, we have reconstructed the 3D surface of the target cell. We have employed this technique in experiments for the analysis of red blood cell morphology. Based on the constructed 3D surface images of diverse-shaped red blood cells, we quantified structural parameters including cell surface area, volume, sphericity, and surface roughness, which demonstrates the potential application of this cell rotation technique for cellular morphological analysis. [ABSTRACT FROM AUTHOR]

A newly developed instrument comprising a near ambient pressure (NAP) photoemission electron microscope (PEEM) and a tunable deep ultraviolet (DUV) laser source is described. This NAP-PEEM instrument enables dynamic imaging of solid surfaces in gases at pressures up to 1 mbar. A diode laser (976 nm) can illuminate a sample from the backside for in situ heating in gases up to 1200 K in minutes. The DUV laser with a tunable wavelength between 175 nm and 210 nm is perpendicularly incident onto the sample surface for PEEM imaging of a wide spectrum of solids with different surface work functions. Using this setup, we have first demonstrated spatiotemporal oscillation patterns of CO oxidation reaction on Pt(110) from high vacuum to NAPs and gas-induced restructuring of metal nanostructures in millibar gases. The new facility promises important applications in heterogeneous catalysis, electrochemical devices, and other surface processes under nearly working conditions. [ABSTRACT FROM AUTHOR]

Surface microscopy of individual biological cells is essential for determining the patterns of cell migration to study the tumor formation or metastasis. This paper presents a correlated and effective theoretical and experimental technique to automatically address the biophysical and mechanical properties and acquire live images of biological cells which are of interest in studying cancer. In the theoretical part, a distributed-parameters model as the comprehensive representation of the microcantilever is presented along with a model of the contact force as a function of the indentation depth and mechanical properties of the biological sample. Analysis of the transfer function of the whole system in the frequency domain is carried out to characterize the stiffness and damping coefficients of the sample. In the experimental section, unlike the conventional atomic force microscope techniques basically using the laser for determining the deflection of microcantilever's tip, a piezoresistive microcantilever serving as a force sensor is implemented to produce the appropriate voltage and measure the deflection of the microcantilever. A micromanipulator robotic system is integrated with the MATLAB® and programmed in such a way to automatically control the microcantilever mounted on the tip of the micromanipulator to achieve the topography of biological samples including the human corneal cells. For this purpose, the human primary corneal fibroblasts are extracted and adhered on a sterilized culture dish and prepared to attain their topographical image. The proposed methodology herein allows an approach to obtain 2D quality images of cells being comparatively cost effective and extendable to obtain 3D images of individual cells. The characterized mechanical properties of the human corneal cell are furthermore established by comparing and validating the phase shift of the theoretical and experimental results of the frequency response. [ABSTRACT FROM AUTHOR]

A pulsed mirror electron microscope was developed for imaging laser-induced processes on the nanosecond time scale. Variations of the electronic structure of the surface are imaged. The evaporation or deposition of an atomic monolayer is readily detected. Pulsed mirror electron microscopy is an alternative technique to pulsed photoelectron microscopy for tracking chemical reactions. In addition, gas flow above the surface and laser-induced ablation of absorbing layers at the back surface of a dielectric can be probed, exploiting electron scattering and capacitive coupling, respectively. Presently, the space/time resolution is limited by the competition between electron shot noise and illumination aperture to 1 μm/5 ns. The illuminating electron pulses are supplied by a laser-driven robust ZrC-covered Re cathode. This device can be operated in a high vacuum of 10[sup -5] mbar either as a photo or a thermal electron emitter. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A multichannel scanning system for magnetic surface imaging composed of 16 magnetoresistive sensors has been developed. A gray scale, from 0 to 255, was used to represent the magnetic signal detected by each sensor when the sample was moved above the scanner. Measurements and calibration were performed using magnetic surfaces with different shapes and samples with similar profiles, but different magnetization intensities. The system was sufficiently sensitive to detect gradients and discontinuities on the magnetic map. The 16 channel images were numerically processed to obtain a smooth representation of the magnetic map using the LabView™ Image Vision package. [ABSTRACT FROM AUTHOR]

We report a microwave surface imaging technique using a near-field scanning microwave microscope with a tunable resonance cavity. By tuning the resonance cavity, we could demonstrate improved sensitivity and spatial resolution of the topographic image of YBa[sub 2]Cu[sub 3]O[sub y] thin films on MgO substrates. By measuring the shift of resonant frequency and the change of quality factor, we obtained near-field scanning microwave images with a spatial resolution better than 4 μm at an operating frequency of f=1–1.5 GHz. The principal of operation could be explained by the perturbation theory of a coaxial resonant cavity, considering the radius of the probe tip, the sample–tip distance, and the impedance matching. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Describes a compact electrostatic low-energy electron microscope. Optimization electron optical system of the microscope; Separation of beams using magnetic sector with small deflection angle; Magnification rate of the three-lens projector system.

Atomic force microscopy (AFM) is one of the most important tools in nanotechnology and surface science. Because of recent developments, nowadays, it is also used to study dynamic processes, such as thin film growth and surface reaction mechanisms. These processes often take place at high temperature and there is a clear need to extend the current operating temperature range of AFM. This letter describes a heating stage and a modified AFM that extends the maximum operating temperature to 750 °C. Atomic step resolution is obtained up to 500 °C in ambient and even up to 750 °C in vacuum. [ABSTRACT FROM AUTHOR]

We report on a scanning electron-spin-resonance microscopy based on a microwave near-field probe. The probe consists of an open dielectric resonator with a thin-slit aperture. The spatial resolution in one direction is determined by the slit width and can be varied between 1 and 100 µm, while the spatial resolution in the perpendicular direction is ∼10 times larger. We demonstrate spatially-resolved measurements on diphenyl-picryl-hydrazil samples on a substrate. A sensitivity of 10[sup 11] spins could be achieved using a 4-µm-wide slit operating at 8.5 GHz and in a contact mode. [ABSTRACT FROM AUTHOR]

A new type of heating specimen holder which allows reflection electron microscopy (REM) imaging with incident and azimuthal angle control is described. A REM image is presented, from a bulk specimen whose surface was prepared in situ, and shows strong contrasts due to atomic steps. [ABSTRACT FROM AUTHOR]

Examines the etching phenomena in scanning tunneling microscopy (STM) of the smooth surface of single crystals of high temperature superconductors. Specification of the etching and imaging at room temperature; Formation of lines and pits in the surface; Uses of STM.

The article discusses a research which described a scanning tunneling microscopy sample transfer design and its integration into a vertical molecular beam epitaxy (MBE) system instead of horizontal growth chambers. The description of the MBE system is detailed. The STM system attachment is described. Cassette and transfer line modifications are presented.

The use of scientific instruments generally requires prior knowledge and skill on the part of operators, and thus, the obtained results often vary with different operators. The autonomous operation of instruments producing reproducible and reliable results with little or no operator-to-operator variation could be of considerable benefit. Here, we demonstrate the autonomous operation of an atomic force microscope using a machine learning-based object detection technique. The developed atomic force microscope was able to autonomously perform instrument initialization, surface imaging, and image analysis. Two cameras were employed, and a machine-learning algorithm of region-based convolutional neural networks was implemented, to detect and recognize objects of interest and to perform self-calibration, alignment, and operation of each part of the instrument, as well as the analysis of obtained images. Our machine learning-based approach could be generalized to apply to various types of scanning probe microscopes and other scientific instruments. [ABSTRACT FROM AUTHOR]

Atomic-scale characteristics of surfaces, including their structure, chemical reactivity, and electronic properties, determine their roles in multiple fields of science and technology, e.g., as coatings, catalysts, and device components. As such, it is of utmost importance to study the atomic arrangement and atomic-scale physico-chemical properties of surfaces in real space in a robust and reliable manner. A powerful technique for achieving this goal is scanning probe microscopy (SPM). Here, we present an overview of SPM-based techniques for atomic-resolution surface imaging and spectroscopy and highlight selected advances in the field. We also discuss current challenges of SPM-based techniques for atomic-resolution surface studies. [ABSTRACT FROM AUTHOR]

The use of biodiesel can reduce dependence on diesel, and the compression ignition (CI) engine's performance with biodiesel is substantially low but could be improved by emulsifying nano-additives. Biodiesel production and performance in CI engines using a homogeneous catalyst is less efficient, expensive, and time-consuming. In this research article, magnesium-doped calcium oxide (Mg–CaO), a novel heterogeneous nanocatalyst, was synthesized and then used to generate biodiesel from Sapindus trifoliatus seed oil. The catalyst surface characterization was analyzed using the surface imaging method, energy dispersive x-ray analysis, x-ray diffraction analysis, and Fourier-transform infrared spectroscopy. Then, the nanocatalyst (30 ppm Mg–CaO) is emulsified in its nano form with the Sapindus trifoliatus biodiesel (STBD) at B25 (STB25% + diesel75%) blend and investigated in the CI engine. The highest yield of 91.75% of biodiesel was achieved at 58 °C, 73 min, 4% catalyst concentration (w/w), and 15:1 methanol:oil molar ratio. The performance results were obtained using STBD25, STBD25 blended with CaO nano-additives (STBD25 + 30 ppm CaO) and STBD25 blended with Mg-doped CaO nano-additives (STBD25 + 30ppm Mg–CaO) are compared to the baseline values obtained from diesel. From the comparison, it is revealed that STBD25 + 30ppm Mg–CaO has a greater influence on combustion, performance, and emission characteristics as follows: (i) in-cylinder pressure increased by 3.22%, 6.24%, and 9.02%, (ii) heat release rate increased by 1.68%, 16.69%, and 32.5%, (iii) brake thermal efficiency is found to be increased by 4.56%, 8.23%, and 11.79%, (iv) hydrocarbon (HC) decreased by 21.12%, 6.06%, and 11.43%, (v) carbon monoxide (CO) decreased by 0.04%, 0.01%, and 0.01%, and (vi) smoke decreased by 22.61%, 8.11%, and 14.25%, compared with diesel, STBD25 + 30 ppm CaO, and STBD25 at full load conditions. Oxides of nitrogen (NOx) released while using STBD25+Mg-doped CaO in CI engine were observed to decrease compared with STBD25 and STBD25+CaO (by 10.72% and 18.64%) and an increase compared with diesel (by 8.64%). [ABSTRACT FROM AUTHOR]

In order to address the complexity of chemical analysis of biological systems, time-of-flight secondary ion mass spectrometry (ToF-SIMS), x-ray photoelectron spectroscopy (XPS), and x-ray photoemission electron microscopy (XPEEM) were used for combined surface imaging of a biological tissue formed around a surface neural device after implantation on a nonhuman primate brain. Results show patterns on biological tissue based on extracellular matrix (ECM) and phospholipid membrane (PM) molecular fragments, which were contrasted through principal component analysis of ToF-SIMS negative spectrum. This chemical differentiation may indicate severe inflammation on tissue with an early case of necrosis. Quantification of the elemental composition and the chemical bonding states on both ECM-rich and PM-rich features was possible through XPS analysis from survey and high-resolution spectra, respectively. Variable amounts of carbon (68%–80.5%), nitrogen (10%–2.4%), and oxygen (20.8%–16.5%) were detected on the surface of the biological tissue. Chlorine, phosphorous sodium, and sulfur were also identified in lower extends. Besides that, analysis of the C 1s high-resolution spectra for the same two regions (ECM and PM ones) showed that a compromise between C—C (41.8 at. %) and C—N/C—O (35.6 at. %) amounts may indicate a strong presence of amino acids and proteoglycans on the ECM fragment-rich region, while the great amount of C—C (70.1 at. %) on the PM fragment-rich region is attributed to the large chains of fatty acids connected to phospholipid molecules. The micrometer-scale imaging of these chemical states on tissue was accomplished through XPEEM analysis. The C—C presence was found uniformly distributed across the entire analyzed area, while C—N/C—O and C=O were in two distinct regions. The combination of ToF-SIMS, XPS, and XPEEM is shown here as a powerful, noninvasive approach to map out elemental and chemical properties of biological tissues, i.e., identification of chemically distinct regions, followed by quantification of the surface chemical composition in each distinct region. [ABSTRACT FROM AUTHOR]

The morphology of surface features generated by dislocations present at 4H-SiC epitaxial layer surfaces was investigated by forescattered electron detection (FED) inside a conventional scanning electron microscope. Various growth pit morphologies were correlated to dislocation types using molten KOH etching. Specifically, sharp-apex pits and stripe-shaped pits were consistently linked to screw and edge dislocations, respectively. The size and depth of these growth pits were measured by atomic force microscopy (AFM). Tail-like features were observed by FED emanating from sharp-apex pits and verified by Nomarski optical microscopy (NOM). A mechanism is proposed to explain the FED contrast exhibited by these tail-like features. This mechanism relates the nature of step-flow and spiral growth in the wake of a screw dislocation to the surface distortions resulting in such tail-like features. The Burgers vector direction can thus be determined based on a purely morphological analysis of these tail-like features. The results of this study illustrate the various capabilities of FED for surface imaging as compared to AFM and NOM. The potential for utilizing FED to map dislocation-associated growth pits is discussed. [ABSTRACT FROM AUTHOR]

InGaAs quantum dots (QDs) embedded in tensile-strained GaAs1-xPx (x=0.0–0.45) barrier layers are grown using low-pressure metal-organic chemical-vapor deposition. Variable-temperature photoluminescence (PL) measurement demonstrates that the lowest-energy QD transition can be blueshifted up to 90 nm compared with similar structures utilizing GaAs barriers. Temperature-dependent PL measurements and atomic force microscopy surface imaging show that the InGaAs QDs grown on GaAsP exhibit reduced height, which is consistent with shorter-wavelength emission. Preliminary results from broad stripe (100 μm wide) diode lasers utilizing two stacks of InGaAs QDs embedded in GaAs0.82P0.18 barriers exhibit a 30% reduction in threshold current density compared with similar laser structures which have GaAs barriers. [ABSTRACT FROM AUTHOR]

Epitaxially grown W/NbN nanolayers are superlattice materials that exhibit a hardness at small bilayer repeat periods which exceed the hardness predicted by the rule of mixtures for normal composites. Interfaces in the bilayered superlattice play a critical role in the superhardening process. The objective of this investigation was to examine the behavior of the superlattice material, W/NbN. Nanoindentations and in situ surface imaging were conducted over a range of applied loads on samples of W/NbN with two different bilayer periods (Λ=5.6 and 10.4 nm), and monolithic samples of the niobium nitride (NbN) ceramic and the tungsten (W) metal which comprise the superlattice material. Shallow nanoindentations were made to a depth equal to the individual layer thicknesses of the epitaxially grown W/NbN nanolayers in order to investigate the individual interface effect. The mechanical properties were determined using the Oliver and Pharr method and compared for all the samples. The energies of indentation are calculated. The characteristics of the material pileup resulting from the nanoindentations are determined from the scanned surface images. An increase in hardness is observed in the superlattice materials at deeper indentation depths. The results indicate that this increase in hardness is related to the nature of the interface between the layers in the superlattice materials. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The role of curvature effects, in the thermal-field (TF) emission of electrons from nanotips, has been investigated. It is found that for field emitter tips having tip radius of curvature R a < 50 nm, the error on using the planar tunneling potential to evaluate the current density is significant compared to the curvature-corrected potential. Furthermore, the error is found to be strongly temperature dependent at low apex fields, whereas at high fields, it is only moderate. For emitter tips having tip radius R a ≥ 5 nm, a unified expression for current density applicable for field, thermal-field, and thermionic emission is obtained. In the analysis, a single linearization point corresponding to the peak of the normal energy distribution of electrons is chosen, about which the Gamow exponent is expanded. The temperature-dependent curvature-corrected current density equation is numerically validated against a benchmark that performs the current density integral with the Kemble form of the Wentzel–Kramers–Brillouin transmission coefficient up to the peak of the tunneling potential, while above the barrier, the Morse transmission coefficient is used. The agreement is found to be good. It is inferred that the curvature plays a significant role in field and thermal-field emission, whereas in thermionic emission, it is not as important. In the limit where the apex radius of curvature R a → ∞ , it is able to retrieve the Murphy–Good equation as well as the Richardson–Laue–Dushman equation in their respective limits. [ABSTRACT FROM AUTHOR]

PbTe-based compounds are excellent candidates for the different types of optical detector applications from near to far IR ranges. In the present work, a technology has been developed for the fabrication of Pb 1 − x Sn x Te compositions, doped with In, on a thin amorphous substrate (polyimide). The film preparation was performed by the electron gun evaporation method. The systematic study of structure and transport properties (Hall coefficient and electric conductivity) in the entire temperature range of 10–300 K for Pb 1 − x Sn x Te:In films (x = 0 , 0.1, 0.2) was investigated. It was studied that the photoconductivity of the films in the telecom wavelength range, including kinetics, sensitivity, and noise equivalent power, has been conducted and it discovered persistent photoconductivity for all compositions at the temperature T < 21 K. The results of the work have promising potential to use poly(nano) crystalline Pb 1 − x Sn x Te:In films on an amorphous substrate both for photodetection in the telecom wavelength range and for the creation of all-optical neuromorphic systems, cooled memory, and logic elements operating at the low energy of laser pulses. [ABSTRACT FROM AUTHOR]

Efficient and accurate object identification and 3D reconstruction are crucial for processing image information in visual imaging. Here, we propose a novel scheme for all-optical 2D contour identification and 3D reconstruction based on optical Brewster interfaces. It is revealed that 2D amplitude and phase contours for high-contrast and low-contrast objects can be identified, which is attributed to the 1D and 2D light fields manipulated by the photonic spin Hall and the Brewster effects. The 3D model can be reconstructed by rotating or slicing the high-contrast objects and by inverting the thickness of the low-contrast objects. The study potentially opens up opportunities in applications such as intelligent driving and microscopic imaging. [ABSTRACT FROM AUTHOR]

Sub-5 nm lithography and metrology are the key technologies for more CMOS and beyond CMOS nanoelectronics. To keep up with scaling down of nanoelectronic components, novel instrumentation for nanometer precise placement, overlay alignment, and measurement are essential to enable fabrication of next generation nanoelectronic systems. In particular, scanning probe microscopy (SPM) based methods for surface modification and measurement are the emerging techniques for producing and testing of sub-5 nm features. In this article, the authors demonstrate nanoscale lithography and coordinate metrology technologies, both being based on SPM methodology. Scanning probes with a piezoresistive deflection read-out and an integrated deflection actuator, later on referred to as the active piezoresistive cantilevers, were used for lithography employing field emission patterning. They were also integrated with the so-called nanomeasuring machine (NPM) and used for surface imaging, which made it possible to measure the structure dimensions in the 25 × 25 × 5 mm3 space with 0.1 nm resolution and great accuracy. The basic NPM concept relies on a unique arrangement, enabling the so-called Abbe error-free measurements in all axes over the total scan range. The combination of the active piezoresistive cantilevers and NPM technologies makes it possible to store the exact location on the investigated surface, which can be found again with an accuracy of less than 2.5 nm. This system is also predestinated for the critical dimension, quality, and overlay control. [ABSTRACT FROM AUTHOR]

The oscillating CO oxidation is investigated on a Pt-field emitter tip by using the field ion mode of surface imaging of Oad sites with O2 as imaging gas. Based on data of the titration reactions [V. Gorodetskii, W. Drachsel, and J. H. Block, J. Chem. Phys. 100, C. E. UPDATE (1994)], external control parameters for the regions of bistability and of self-sustained isothermal oscillations could be found. On a field emitter tip, oscillations can be generated in a rather large parameter space. The anticlockwise hysteresis of O+2 ion currents in temperature cycles occurs in agreement with results on single crystal planes. Unexpected regular oscillation sequences could occasionally be obtained on the small surface areas of a field emitter tip and measured as function of the CO partial pressure and of the temperature. Different stages within oscillating cycles were documented by field ion images. Oscillations of total ion currents are correlated with variations in the spatial brightness of field ion images. In the manifold of single crystal planes of a field emitter {331} planes around the {011} regions are starting points for oscillations which mainly proceed along [100] vicinals. This excludes the {111} regions from autonomous oscillations. With slightly increased CO partial pressures fast local oscillations at a few hundred surface sites of the Pt(001) plane display short-living CO islands of 40 to 50 Å diameter. Temporal oscillations of the total O+2 ion current are mainly caused by surface plane specific spatial oscillations. The synchronization is achieved by diffusion reaction fronts rather than by gas phase synchronization. [ABSTRACT FROM AUTHOR]

A double sample holder supporting both a metal sample and an insulator crystal for high-resolution scanning probe microscopy experiments is described. The metal sample serves as a substrate for tip preparation and tip functionalization to efficiently and reliably enable high-resolution studies of the adjacent insulator surface. Imaging of Ag(111)/mica, Au(111)/mica, CaF2(111), and calcite(104) surfaces is demonstrated at 5 K, including images on calcite(104) produced with a CO terminated tip, which was prepared on the adjacent metal sample. [ABSTRACT FROM AUTHOR]

Optical computing harnesses the speed of light to perform vector-matrix operations efficiently. It leverages interference, a cornerstone of quantum computing algorithms, to enable parallel computations. In this work, we interweave quantum computing with classical structured light by formulating the process of photonic matrix multiplication using quantum mechanical principles such as state superposition and subsequently demonstrate a well-known algorithm, namely, Deutsch–Jozsa's algorithm. This is accomplished by elucidating the inherent tensor product structure within the Cartesian transverse degrees of freedom of light, which is the main resource for optical vector-matrix multiplication. To this end, we establish a discrete basis using localized Gaussian modes arranged in a lattice formation and demonstrate the operation of a Hadamard gate. Leveraging the reprogrammable and digital capabilities of spatial light modulators, coupled with Fourier transforms by lenses, our approach proves adaptable to various algorithms. Therefore, our work advances the use of structured light for quantum information processing. [ABSTRACT FROM AUTHOR]

Arsenic is one of the most toxic elements present in the environment, especially in water. The World Health Organization (WHO) recommends a maximum concentration of arsenic in drinkable water of 10 μg/l (10 ppb). Sensors implementing Surface Enhanced Raman Scattering (SERS) can detect chemical species at low concentrations. The aim of this study is to compare two kinds of silver-coated SERS substrates for detection and speciation of trace, trivalent and pentavalent, inorganic arsenic compounds. One type of substrate was prepared by a classical thermal evaporation technique, and the second type by an electroless process. The thermally evaporated substrates allowed the detection of As(III) only, at a limit of detection (LOD) of approximately 50 mg/l, whereas As(V) could not be detected at any analyte concentration. The electroless substrates allow one to differentiate As(III) and As(V) with a LOD 1 μg/l (1 ppb) equal for each valency, below the WHO recommendation. The electroless substrates show a very large sensitivity across up to five orders of magnitude in terms of analyte concentration. Although the SERS intensity shows a nonlinear behavior over this range of concentrations, these preliminary results are encouraging in the framework of the demonstration of trace As SERS sensors in drinkable water. [ABSTRACT FROM AUTHOR]

Imaging mass spectrometry (IMS) is a powerful analytical technique widely used in biology, chemistry, and materials science fields that continue to expand. IMS provides a qualitative compositional analysis and spatial mapping with high chemical specificity. The spatial mapping information can be 2D or 3D depending on the analysis technique employed. Due to the combination of complex mass spectra coupled with spatial information, large high-dimensional datasets (hyperspectral) are often produced. Therefore, the use of automated computational methods for an exploratory analysis is highly beneficial. The fast-paced development of artificial intelligence (AI) and machine learning (ML) tools has received significant attention in recent years. These tools, in principle, can enable the unification of data collection and analysis into a single pipeline to make sampling and analysis decisions on the go. There are various ML approaches that have been applied to IMS data over the last decade. In this review, we discuss recent examples of the common unsupervised (principal component analysis, non-negative matrix factorization, k-means clustering, uniform manifold approximation and projection), supervised (random forest, logistic regression, XGboost, support vector machine), and other methods applied to various IMS datasets in the past five years. The information from this review will be useful for specialists from both IMS and ML fields since it summarizes current and representative studies of computational ML-based exploratory methods for IMS. [ABSTRACT FROM AUTHOR]

In this paper, we present in detail the design, both electromagnetic and mechanical, the fabrication, and the test of the first prototype of a Scanning Microwave Microscope (SMM) suitable for a two-port transmission measurement, recording, and processing the high frequency transmission scattering parameter S21 passing through the investigated sample. The S21 toolbox is composed by a microwave emitter, placed below the sample, which excites an electromagnetic wave passing through the sample under test, and is collected by the cantilever used as the detector, electrically matched for high frequency measurements. This prototype enhances the actual capability of the instrument for a sub-surface imaging at the nanoscale. Moreover, it allows the study of the electromagnetic properties of the material under test obtained through the measurement of the reflection (S11) and transmission (S21) parameters at the same time. The SMM operates between 1 GHz and 20 GHz, current limit for the microwave matching of the cantilever, and the high frequency signal is recorded by means of a two-port Vector Network Analyzer, using both contact and no-contact modes of operation, the latter, especially minded for a fully nondestructive and topography-free characterization. This tool is an upgrade of the already established setup for the reflection mode S11 measurement. Actually, the proposed setup is able to give richer information in terms of scattering parameters, including amplitude and phase measurements, by means of the two-port arrangement. [ABSTRACT FROM AUTHOR]

Al2O3 [20nm, atomic layer deposition (ALD)] and SiO films' [25 nm, physical vacuum deposition (PVD)] single barriers as well as hybrid barriers of the Al2O3 /SiO or SiO/Al2O3 have been deposited onto single 100 nm thick tris-(8-hydroxyquinoline) aluminum (AlQ3) organic films made onto silicon wafers. The defects in the different barrier layers could be easily observed as nonfluorescent AlQ3 black spots, under ultraviolet light on the different systems stored into accelerated aging conditions (85 °C/85% RH, ~2000 h). It has been observed that all devices containing an Al2O3 layer present a lag time s from which defect densities of the different systems start to increase significantly. This is coherent with the supposed pinhole-free nature of fresh, ALD-deposited, Al2O3 films. For t>s, the number of defect grows linearly with storage time. For devices with the single Al2O3 barrier layer, s has been estimated to be 64 h. For t>s, the defect occurrence rate has been calculated to be 0.268/ cm2/h. Then, a total failure of fluorescence of the AlQ3 film appears between 520 and 670 h, indicating that the Al2O3 barrier has been totally degraded by the hot moisture. Interestingly, the device with the hybrid barrier SiO/Al2O3 shows the same characteristics as the device with the single Al2O3 barrier (τ = h; 0.246/cm2/h for t>τ), indicating that Al2O3 ALD is the factor that limits the performance of the barrier system when it is directly exposed to moisture condensation. At the end of the storage period (1410 h), the defect density for the system with the hybrid SiO/Al2O3 barrier is 120/cm2. The best sequence has been obtained when Al2O3 is passivated by the SiO layer (Al2O3 / SiO). In that case, a large lag time of 795 h and a very low defect growth rate of 0.032/cm2/h (t>s) have been measured. At the end of the storage test (2003 h), the defect density remains very low, i.e., only 50/cm2. On the other hand, the device with the single PVD-deposited SiO barrier layer shows no significant lag time (τ ~ 0), and the number of defects grows linearly from initial time with a high occurrence rate of 0.517/cm2/h. This is coherent with the pinhole-full nature of fresh, PVDdeposited, SiO films. At intermediate times, a second regime shows a lower defect occurrence rate of 0.062/cm2/h. At a longer time span (t>1200 h), the SiO barrier begins to degrade, and a localized crystallization onto the oxide surface, giving rise to new defects (occurrence rate 0.461/cm2/h), could be observed. At the end of the test (2003 h), single SiO films show a very high defect density of 600/cm2. Interestingly, the SiO surface in the Al2O3 /SiO device does not appeared crystallized at a high time span, suggesting that the crystallization observed on the SiO surface in the AlQ3/SiO device rather originates into the AlQ3 layer, due to high humidity ingress on the organic layer through SiO pinholes. This has been confirmed by atomic force microscopy surface imaging of the AlQ3/SiO surface showing a central hole in the crystallization zone with a 60nm depth, deeper than SiO thickness (25nm). Using the organic AlQ3 sensor, the different observations made in this work give a quantitative comparison of defects' occurrence and growth in ALD-deposited versus PVD-deposited oxide films, as well as in their combination PVD/ALD and ALD/PVD. [ABSTRACT FROM AUTHOR]

Optical tweezers can control the position and orientation of individual colloidal particles in solution. Such control is often desirable but challenging for single-particle spectroscopy and microscopy, especially at the nanoscale. Functional nanoparticles that are optically trapped and manipulated in a three-dimensional (3D) space can serve as freestanding nanoprobes, which provide unique prospects for sensing and mapping the surrounding environment of the nanoparticles and studying their interactions with biological systems. In this perspective, we will first describe the optical forces underlying the optical trapping and manipulation of microscopic particles, then review the combinations and applications of different spectroscopy and microscopy techniques with optical tweezers. Finally, we will discuss the challenges of performing spectroscopy and microscopy on single nanoparticles with optical tweezers, the possible routes to address these challenges, and the new opportunities that will arise. [ABSTRACT FROM AUTHOR]

Transient heat loading and high-flux particle loading on plasma facing components in fusion reactors can lead to surface melting and possible erosion. Helium-induced fuzz formation is expected to exacerbate thermal excursions, due to a significant drop in thermal conductivity. The effect of heating in edge-localized modes (ELMs) on the degradation and erosion of a tungsten (W) fuzz surface was examined experimentally in the Ultra High Flux Irradiation-II facility at the Center for Materials Under Extreme Environment. W foils were first exposed to low-energy He+ ion irradiation at a fluence of 2.6 × 1024 ions m−2 and a steady-state temperature of 1223 K. Then, samples were exposed to 1000 pulses of ELM-like heat loading, at power densities between 0.38 and 1.51 GW m−2 and at a steady-state temperature of 1223 K. Comprehensive erosion analysis measured clear material loss of the fuzz nanostructure above 0.76 GW m−2 due to melting and splashing of the exposed surface. Imaging of the surface via scanning electron microscopy revealed that sufficient heating at 0.76 GW m−2 and above caused fibers to form tendrils to conglomerate and form droplets. Repetitive thermal loading on molten surfaces then led to eventual splashing. In situ erosion measurements taken using a witness plate and a quartz crystal microbalance showed an exponential increase in mass loss with energy density. Compositional analysis of the witness plates revealed an increase in the W 4f signal with increasing energy density above 0.76 GW m−2. The reduced thermal stability of the fuzz nanostructure puts current erosion predictions into question and strengthens the importance of mitigation techniques. [ABSTRACT FROM AUTHOR]

This paper presents an 8 x 24 element, 100 μm-pitch, 20 MHz ultrasound imager based on a piezoelectric micromachined ultrasonic transducer (PMUT) array having integrated acoustic waveguides. The 70 im diameter, 220 μm\ long waveguides function both to direct acoustic waves and to confine acoustic energy, and also to provide mechanical protection for the PMUT array used for surface-imaging applications such as an ultrasonic fingerprint sensor. The imager consists of a PMUT array bonded with a CMOS ASIC using wafer-level conductive eutectic bonding. This construction allows each PMUT in the array to have a dedicated front-end receive amplifier, which together with on-chip analog multiplexing enables individual pixel read-out with high signal-to-noise ratio through minimized parasitic capacitance between the PMUT and the front-end amplifier. Finite element method simulations demonstrate that the waveguides preserve the pressure amplitude of acoustic pulses over distances of 600 μm\. Moreover, the waveguide design demonstrated here enables pixel-by-pixel readout of the ultrasound image due to improved directivity of the PMUT by directing acoustic waves and creating a pressure field with greater spatial uniformity at the end of the waveguide. Pulse-echo imaging experiments conducted using a one-dimensional steel grating demonstrate the array's ability to form a two-dimensional image of a target. [ABSTRACT FROM AUTHOR]