Backscattered Electron Detector Research Articles

Nanoscale Estimation of Coating Thickness on Substrates via Standardless BSE Detector Calibration

The thickness of electron transparent samples can be measured in an electron microscope using several imaging techniques like electron energy loss spectroscopy (EELS) or quantitative scanning transmission electron microscopy (STEM). We extrapolate this method for using a back-scattered electron (BSE) detector in the scanning electron microscope (SEM). This brings the opportunity to measure the thickness not just of the electron transparent samples on TEM mesh grids, but, in addition, also the thickness of thin films on substrates. Nevertheless, the geometry of the microscope and the BSE detector poses a problem with precise calibration of the detector. We present a simple method which can be used for such a type of detector calibration that allows absolute (standardless) measurement of thickness, together with a proof of the method on test samples.

Silica bodies of Selaginella erythropus: Detection, morphology and development

Selaginellaceae (Lycopodiophyta), an early divergent group of vascular plants, are a species-rich and taxonomically challenging family. Here we study silica bodies on the leaves of a prominently studied Selaginella, S. erythropus, with various methods of microscopy and energy disperse X-ray analysis (EDX) to characterize their properties in mature and emerging leaves.To detect silica bodies, a light microscope or a fluorescence microscope can be used to reveal colorless silica body protrusions in the epidermal cell walls. Silica bodies show as light spots with scanning electron microscopy (SEM). However, the recent tabletop SEM featured with low accelerating voltage and backscattered electron detectors provides a better contrast than standard SEM. EDX shows that these protrusions on leaf surfaces are silica bodies and that trichome apices and some stomata also have silica deposits. Atomic force microscopy provides three-dimensional images and quantitative measurements, but with an upper limit on silica body size. Under transmission electron microscopy silica bodies are characterized as compact electron-dense particles, gradually thinning and mingling with the cell wall.These analyses recognized two major forms of silica bodies, conical (small and large subforms) and sinuate-carinate. Distinct forms are found on different types of epidermal cells. Patterns on a leaf surface differ between the four types of leaf surface, dorsal and ventral surfaces of dorsal and ventral leaves, and may have taxonomic value.The silicification process on a young leaf begins from the central part. Large conical silica bodies appear first, along leaf margins and trichomes. Then, small conical silica bodies develop. Sinuate-carinate forms arise from the merger of large conical forms.A full understanding of the functional significance of silica bodies in Selaginella has yet to be developed, but we hope this report can help researchers detect silica bodies, and inspire more studies.

Influence of Isothermal Holding on the Microstructure and Mechanical Properties of Electron Beam Welded Dissimilar Inconel 718/ATI 718Plus\xae Joint

Microstructural changes of the Inconel 718 and ATI 718Plus® base materials and the fusion zone caused by the isothermal hold at 760 °C for up to 500 h were investigated. The evaluation was performed using a scanning electron microscope with backscattered electrons detector and scanning transmission electron microscopy supported by energy-dispersive x-ray spectroscopy. Furthermore, to evaluate the effect of microstructural changes on mechanical properties Vickers microhardness measurements were performed. Exposure of welded joint at high temperature led to coarsening and/or dissolution of main strengthening phases’ particles and nucleation and growth of plate-like precipitates. In the interdendritic region of the fusion zone, the transformation of the Laves phase to a complex cluster of precipitates contained σ phase had taken place. Analysis of microstructure and microhardness measurements showed that ATI 718Plus has better mechanical properties and microstructural stability at elevated temperature than Inconel 718.

Enhancing the defect contrast in ECCI through angular filtering of BSEs

In this study, an annular multi-segment backscattered electron (BSE) detector is used in back scatter geometry to investigate the influence of the angular distribution of BSE on the crystalline defect contrast in electron channeling contrast imaging (ECCI). The study is carried out on GaAs and Ge layers epitaxially grown on top of silicon (Si) substrates, respectively. The influence of the BSE detection angle and landing energy are studied to identify the optimal ECCI conditions. It is demonstrated that the angular selection of BSEs exhibits strong effects on defect contrast formation with variation of beam energies. In our study, maximum defect contrast can be obtained at BSE detection angles 53–65° for the investigated energies 5, 10 and 20 keV. In addition, it is found that higher beam energy is favorable to reveal defects with stronger contrast whereas lower energy ( ≤ 5 keV) is favorable for revealing crystalline defects as well as with topographic features on the surface. Our study provides optimal ECCI conditions, and therefore enables a precise and fast detection of threading dislocations in lowly defective materials and nanoscale 3D semiconductor structures where signal to noise ratio is especially important. A comparison of ECCI with BSE and secondary electron imaging further demonstrates the strength of ECCI in term of simultaneous detection of defects and morphology features such as terraces with atomic step heights.

In Operando Monitoring by Analysis of Backscattered Electrons during Electron Beam Melting

Additive manufacturing by electron beam melting (EBM) is a complex process, which still lacks reliable tools for process monitoring. Demanding processing conditions such as high temperature, high vacuum, and X‐ray radiation impede the continuous operation of standard process monitoring devices such as light‐optical camera systems. To overcome this deficit, the detection of backscattered electrons (BSEs) is a highly promising approach. A detection system for BSEs is used for recording the in operando signal during melting inside an EBM system. The acquired data are postprocessed by mapping the data points to spatial coordinates. A comparison between the obtained intensity map and the as‐built surface shows a remarkable correlation, which might be suitable for process monitoring and quality control purposes.

Different surface treatment protocols of a Y-TZP ceramic with a superficial glaze layer

Aim: evaluate the influence of etching time with hydrofluoric acid on the bond strength of a Yttrium-stabilized polycrystalline tetragonal zirconia (Y-TZP) ceramic with a superficial glaze layer and a resin cement. Methods: Y-TZP blocks were cut to obtain 40 samples. They were distributed into four groups (n = 10): control treated by sandblasting with silica-coated alumina (RS) and three glazed experimental groups with different etching times: GS20s, GS60s and GS100s. Cementation was done with a universal adhesive and a resin cement. Two cement cylinders were made in each block. After thermocycling, the shear bond test was performed. Two extra samples of each group were made to obtain profilometry, scanning electron microscopy, mapping and backscattered electron detector images. Energy dispersive spectrometry and goniometry were also performed. Results: Kruskal-Wallis and Dunn tests demonstrated bond strength differences only between the RS (22.10MPa) and the GS groups (GS20s: 8,10Mpa; GS60s: 10.49MPa; GS100s: 7.53MPa) (p = 0.001), but there was no difference among the experimental groups (p > 0.05). The contact angles were 55.33º (RS); 70.78° (GS100s); 48.20º (GS60s) and 28.73º (GS20s). ANOVA and Tukey test demonstrated similar wettability of RS to GS60s and GS100s (p > 0.05), but all the experimental groups were statistically different between them (p < 0.001). Qualitative image analysis revealed an irregular glaze distribution after etching. The thickness of the remaining glaze layer measured by profilometry was 5±1μm (GS20S), 4±1μm (GS60S) and 3±1μm (GS100s). Conclusion: The etching time of glazed zirconia did not influence the adhesive strength of the ceramic to the resin cement.

3D surface topography imaging in SEM with improved backscattered electron detector: Arrangement and reconstruction algorithm

We propose a new SFS (shape from shading) technique for improved 3D surface reconstruction and imaging of relatively smooth surface topography using the scanning electron microscope (SEM). The new arrangement of backscattered electrons detector plates allows decreasing the initial energy of the electron probe, which makes this SEM technique to be suitable for usage on radiation-sensitive samples like biological tissues. Experiments show high effectiveness of the method, which improves both the gradient sensitivity of the signal and the signal to noise ratio.

Lethality, neurotoxicity, morphological, histological and cellular alterations of Ni-Al nanoceramics on the embryo-larval development of Rhinella arenarum

Alumina nanoparticles (NP-Al2O3) are widely used but their environmental effects are unknown, so they can become potentially dangerous. The aim of this study was to evaluate the toxicity of a nanoceramic catalyst Ni/γ-Al2O3 (NC) and NPs involved in their synthesis, γ-Al2O3 support (SPC) and NiO/γ-Al2O3 precursor (PC) on Rhinella arenarum embryo-larval development. The NPs toxicity significantly increased over time obtaining a similar sensitivity to PC and NC (336 h-LC50 = 4.03 and 5.11 mg/L respectively) and very low sensitivity to SPC (336 h-LC50 = 90.83 mg/L). Embryos exposed to SPC and PC exhibited general underdevelopment, axial flexures and behavioral alterations. Pharyngeal and intestinal epithelia alterations at the level of cell surface as dissociation, apoptosis and numerous lysosomes were observed at light and transmission electronic microscopy. Images of scanning electron microscope with backscattered electron detector revealed the presence of nickel in the intestinal epithelium. The increased toxicity of PC could be due to the presence of Ni as oxide which could interfere with vital functions such as breathing and feeding. Taking into account the exponential production and use of these NPs it is expected that their pollution levels will considerably increase and amphibians will be more exposed and at higher risk.

Immediate development of processing windows for selective electron beam melting using layerwise monitoring via backscattered electron detection

The availability of a reliable processing window is the basic requirement for processing new materials via selective electron beam melting (SEBM). Typically, these processing windows are derived by a time-consuming procedure comprising fabrication, metallographic preparation and analysis of standardized specimens for every parameter set. This study demonstrates the immediate development of a processing window during one single SEBM process. An electron optical image acquisition system provides the necessary information for evaluation and subsequent adaption of process parameters. It is shown that this immediate approach delivers processing windows with sufficient accuracy, while the required time is substantially reduced from weeks or even months to several hours.

Preparation and Characterization of TiO₂-PVDF/PMMA Blend Membranes Using an Alternative Non-Toxic Solvent for UF/MF and Photocatalytic Application.

The approach of the present work is based on the use of poly (methylmethacrylate) (PMMA) polymer, which is compatible with PVDF and TiO2 nanoparticles in casting solutions, for the preparation of nano-composites membranes using a safer and more compatible solvent. TiO2 embedded poly (vinylidene fluoride) (PVDF)/PMMA photocatalytic membranes were prepared by phase inversion method. A non-solvent induced phase separation (NIPS) coupled with vapor induced phase separation (VIPS) was used to fabricate flat-sheet membranes using a dope solution consisting of PMMA, PVDF, TiO2, and triethyl phosphate (TEP) as an alternative non-toxic solvent. Membrane morphology was examined by scanning electron microscopy (SEM). Backscatter electron detector (BSD) mapping was used to monitor the inter-dispersion of TiO2 in the membrane surface and matrix. The effects of polymer concentration, evaporation time, additives and catalyst amount on the membrane morphology and properties were investigated. Tests on photocatalytic degradation of methylene blue (MB) were also carried out using the membranes entrapped with different concentrations of TiO2. The results of this study showed that nearly 99% MB removal can be easily achieved by photocatalysis using TiO2 immobilized on the membrane matrix. Moreover, it was observed that the quantity of TiO2 plays a significant role in the dye removal.

Structural Analysis of Mouse Platelets using Serial Block-Face Scanning Electron Microscopy

Platelets are small, anucleate cells in mammalian blood that maintain hemostasis and aggregate to seal leaks at sites of vascular injury, a vital element of wound healing. Upon detecting vascular lesions, blood platelets become activated and release components, such as the Von Willebrand factor, from at least three different storage compartments: alpha-granules, dense granules, and lysosomes. Abnormalities in platelet functions can contribute to thrombosis, atherosclerosis and other diseases. Obtaining cellular structure is critical for gaining better understanding of platelet physiology. We used Serial Block-Face Scanning Electron Microscope (SBF-SEM) to elucidate the 3-D ultrastructure of mouse blood platelets in both the activated and inactivated (resting) states. In SBF-SEM an in-situ ultramicrotome cuts slices of heavy-atom stained cells that are embedded in a resin block. The top surface of the block is then imaged using a back-scattered electron detector, and the process of slicing and imaging is repeated until the desired volume of cells is obtained. A stack of images can then be aligned, and ultrastructure visualized using segmentation software. Based on the segmentation and measurements on images from 4 different platelet activation states, we observed that rapid swelling of alpha-granules is accompanied by matrix decondensation that occurs first in peripheral granules, whereas condensed granules were situated more centrally. Decondensed granules appeared almost adjacent or connected to the plasma membrane. Based on these findings, we propose that the granule matrix organization is an important factor for platelet function, i.e., for timed-release properties of alpha-granule cargo, which could be physiologically important to thrombus formation, wound healing and angiogenesis. This work was supported by the Intramural Research Program of the National Institutes of Biomedical Imaging and Bioengineering, NIH (RDL) and NIH grants R01 HL119393 and R56 HL119393 (BS).

Research on Temporal Leachability of Trace Elements from Opoka-Rocks in The Aspect of Geochemical Environmental Indicators

As part of the work on the trace element concentration in building materials and their leachability to the environment, the analyses of the temporal release of the trace elements group that could play a role as environmental chemical indicator were carried out. For a period of about half a year, in water eluates with different temporal fractions the leachability for: Sr, Ba, Mg, Mn, Zn were determined. Lumpy varieties of the opoka-rocks from the pre-industrial deposits and historical buildings were the material subjected to the analyses. The research methodology covered studies using broad analytics. The phase methods were used in order to uniquely identify the crystalline components of the studied rocks. Mineralogical and petrographic investigations were performed using Olympus BX-51 polarizing microscope and (SEM) FEI Quanta 200FEG electron microscope equipped with an X-ray spectrometer (EDX Genesis) and a backscattered electron detector (BSE). The concentration of these trace elements in water eluates in 8 temporal fractions was carried out in accordance with EA NEN 7375: 2004 and PN-EN ISO 11885 standards using the ICP sequential plasma spectrometer. It was found that the series of leachability of the studied elements in decreasing succession is as follows: Mg> Sr> Zn> Ba> Mn. The highest leachability from the selected elements was found for Mg, which ranged from 0.22 to 1.14 ppm

Development of Al-Fe-(Cu) Series Alloys for Aluminum Cables and the Related Annealing Behaviors

In this work, Al-Fe-(Cu) alloys for aluminum cables were designed and the related annealing behaviors were discussed in detail to help understand the influence of processing and heat treatment on the electrical conductivity and mechanical properties of the studied alloys. The interaction between different solute elements was tracked by using hardness and electrical conductivity testing. The microstructure was investigated by using Electron Backscattered Diffraction (EBSD) technique, along with Scanning Electron Microscopy with Backscattered Electron Detector (BSE). The results show that the conductivities of Al-Fe-Cu alloy increased with the elongated annealing time, and reaches its maximum at 6 h, when annealed at temperatures from 275 °C to 375 °C. The addition of Fe to Al can strengthen the alloy and decrease its conductivity slightly, while the addition of Cu will influence the alloy conductivity significantly. The morphologies of precipitates will change with different amount of alloying elements as well.

On the mechanism of colloidal silica action to improve flow properties of pharmaceutical excipients

The mechanism of colloidal silica action to improve flow properties of pharmaceutical powders is known to be based on inter-particle force disruption by silica particles adhered to the particle surface. In the present article, the kinetic aspects of this action are investigated, focusing on non-spherical particles of different size. Blends comprising microcrystalline cellulose or calcium hydrogen phosphate dihydrate and colloidal silica were examined using powder rheometer. The blends were formulated to represent effects of particle size, surface texture, colloidal silica loading, and mixing time. Pre-conditioning, shear testing, compressibility, and flow energy measurements were used to monitor flow properties. Components and blends were analyzed using particle size analysis and scanning electron microscopy (SEM), using energy dispersive spectroscopy (EDS) and back-scattered electron (BSE) detection to determine surface particle arrangement. All studied parameters were found to have substantial effects on flow properties of powder blends. Those effects were explained by identifying key steps of colloidal silica action, which were found to proceed at substantially different rates, causing the flow properties change over time being dependent on the blend formulation and the component properties.

Evolution of microstructure of Lead free cu/Sn solders and copper oxide phase precipitation in Cu3Sn intermetallic during thermal cycling

Intermetallic layers were formed after Solid Liquid Interdiffusion (SLID). Cu-Sn interdiffusion leads to the formation of two intermetallic layers: Cu6Sn5 and Cu3Sn. In this work, Sn solder was subjected to thermal cycling from −65 to +250 °C at 10 °C/min. After few cycles we noticed the appearance of a new –pillar– shaped phase made of copper oxide. The Intermetallic layers were mechanically tested using die-shear testing. The die-shear resistance appears to be increasing when the number of thermal cycles increases. The microstructure was observed using Backscatter Electron detector (BSD) and Scanning Electron Microscopy (SEM). The composition of the phase was measured using Energy Dispersive x-ray spectroscopy (EDX). It appears that a new copper oxide phase forms after few cycles. As the number of cycles increase, the size and the number of the copper oxide phases increase.

Layerwise monitoring of electron beam melting via backscatter electron detection

PurposeThe purpose of this study is the introduction and validation of a new technique for process monitoring during electron beam melting (EBM).Design/methodology/approachIn this study, a backscatter electron detector inside the building chamber is used for image acquisition during EBM process. By systematic variation of process parameters, the ability of displaying different topographies, especially pores, is investigated. The results are evaluated in terms of porosity and compared with optical microscopy and X-ray computed tomography.FindingsThe method is capable of detecting major flaws (e.g. pores) and gives information about the quality of the resulting component.Originality/valueImage acquisition by evaluating backscatter electrons during EBM process is a new approach in process monitoring which avoids disadvantages restricting previously investigated techniques.

First-Surface Scintillator for Low Accelerating Voltage Scanning Electron Microscopy (SEM) Imaging.

Highly luminescent thin films of zinc tungstate (ZT) have been deposited on top of conventional scintillators (Yttrium Aluminum Perovskite, Yttrium Aluminum Garnet) for electron detection in order to replace the need for a top conducting layer, such as indium tin oxide (ITO) or aluminum, which is non-scintillating and electron absorbing. Such conventional conducting layers serve the single purpose of eliminating electrical charge build-up on the scintillator. The ZT film also eliminates charging, which has been verified by measuring the Duane-Hunt limit and electron emission versus accelerating voltage. The luminescent nature of the ZT film ensures effective detection of low energy electrons from the very top surface of the structure ZT/scintillator, which we call "first-surface scintillator". The cathodoluminescence has been measured directly with a photodetector and spectrally resolved at different accelerating voltages. All results demonstrate the extended range of operation of the first-surface scintillator, while the conventional scintillators with a top ITO layer decline below 5 kV and have practically no output below 2 kV. Scintillators of different types were integrated in a detection system for backscattered electrons (BSE). The quality of the image at high accelerating voltages is comparable with the conventional scintillator and commercial BSE detector, while the image quality at 1 kV from the first-surface scintillator is superior.

Fabrication and Characterization of a High-Performance Multi-Annular Backscattered Electron Detector for Desktop SEM.

Scanning electron microscopy has been developed for topographic analysis at the nanometer scale. Herein, we present a silicon p-n diode with multi-annular configuration to detect backscattering electrons (BSE) in a homemade desktop scanning electron microscope (SEM). The multi-annular configuration enables the enhancement of the topography contrast of 82.11 nA/μm as compared with the commercial multi-fan-shaped BSE detector of 40.08 nA/μm. Additionally, we integrated it with lateral p-n junction processing and aluminum grid structure to increase the sensitivity and efficiency of the multi-annular BSE detector that gives higher sensitivity of atomic number contrast and better surface topography contrast of BSE images for low-energy detection. The responsivity data also shows that MA-AL and MA p-n detectors have higher gain value than the MA detector does. The standard deviation of measurements is no higher than 1%. These results verify that MA p-n and MA-AL detectors are stable and can function well in SEM for low-energy applications. It is demonstrated that the multi-annular (MA) detectors are well suited for imaging in SEM systems.

New Possibilities for State-of-the-Art Electron Microscopy with Fast Backscattered Electron Detectors

New Possibilities for State-of-the-Art Electron Microscopy with Fast Backscattered Electron Detectors

Ion polishing as a method of imaging the magnetic structures in CoNiGa monocrystal

Abstract Magnetic domain structure of magnetic shape memory alloy was observed using backscattered electron detector in scanning electron microscope and using Fresnel imaging in transmission electron microscope. The sample subjected to additional ion polishing allowed observation of the contrast associated with the magnetic structure of the material under conditions that exclude the use of Foucault or Fresnel transmission electron microscopy imaging. The additional research conducted using atomic force microscopy showed a significant relationship between the method of preparation and the magnetic shape memory alloy sample surface.