Secondary Electron Detector Research Articles

Quantitative characterization and comparative study of feather melanosome internal morphology using surface analysis

A successful feather development implies in a precise orchestration of cells in the follicle, which culminates in one of the most complex epidermal structures in nature. Melanocytes contribute to the final structure by delivering melanosomes to the barb and barbule cells. Disturbance to the tissue during the feather growth can damage the final structure. Here, melanosomes seen in an unusual outgrowth on the barb cortex of a flight feather are reported and compared to commonly observed melanosomes embedded in the cortex. Transmission Electron Microscopy in scanning-transmission mode (STEM) generated images coupled with secondary electron detection. The two classes of melanosomes were registered on images combining transmitted and secondary electron signals. Image processing allowed surface analyses of roughness and texture of the internal morphology of these organelles. Results showed that the two classes of melanosomes are significantly distinct internally, indicating that different physiological processes up to feather maturation could have occurred. Surface analysis methods are not regularly used in cell biology studies, but here it is shown that it has great potential for microscopic image analysis, which could add robust information to studies of cell biology events.

Image contrast enhancement of Ni/YSZ anode during the slice-and-view process in FIB-SEM.

Focused ion beam-scanning electron microscopy (FIB-SEM) is a widely used and easily operational equipment for three-dimensional reconstruction with flexible analysis volume. It has been using successfully and increasingly in the field of solid oxide fuel cell. However, the phase contrast of the SEM images is indistinct in many cases, which will bring difficulties to the image processing. Herein, the phase contrast of a conventional Ni/yttria stabilized zirconia anode is tuned in an FIB-SEM with In-Lens secondary electron (SE) and backscattered electron detectors. Two accessories, tungsten probe and carbon nozzle, are inserted during the observation. The former has no influence on the contrast. When the carbon nozzle is inserted, best and distinct contrast can be obtained by In-Lens SE detector. This method is novel for contrast enhancement. Phase segmentation of the image can be automatically performed. The related mechanism for different images is discussed.

High-quality imaging in environmental scanning electron microscopy--optimizing the pressure limiting system and the secondary electron detection of a commercially available ESEM.

In environmental scanning electron microscopy applications in the kPa regime are of increasing interest for the investigation of wet and biological samples, because neither sample preparation nor extensive cooling are necessary. Unfortunately, the applications are limited by poor image quality. In this work the image quality at high pressures of a FEI Quanta 600 (field emission gun) and a FEI Quanta 200 (thermionic gun) is greatly improved by optimizing the pressure limiting system and the secondary electron (SE) detection system. The scattering of the primary electron beam strongly increases with pressure and thus the image quality vanishes. The key to high-image quality at high pressures is to reduce scattering as far as possible while maintaining ideal operation conditions for the SE-detector. The amount of scattering is reduced by reducing both the additional stagnation gas thickness (aSGT) and the environmental distance (ED). A new aperture holder is presented that significantly reduces the aSGT while maintaining the same field-of-view (FOV) as the original design. With this aperture holder it is also possible to make the aSGT even smaller at the expense of a smaller FOV. A new blade-shaped SE-detector is presented yielding better image quality than usual flat SE-detectors. The electrode of the new SE detector is positioned on the sample table, which allows the SE-detector to operate at ideal conditions regardless of pressure and ED.

B13-O-10Low Energy Secondary Electron Imaging for Various Semiconductors using Fountain Detector

Recently, the energy filtered secondary electron (SE) images give fruitful information of the specimen, not only morphology and composition but also surface potential, electrical field etc. Such modern detector has been developed for inlens SEM and outlens detectors were abandoned. We have developed low-pass secondary electron detector (LPSED) for outlens SEM and named “Fountain Detector (FD)”. This detector is composed of bias grid above and electron detector below the specimen. The bias voltage and the geometry of the detector limit the energy and acceptance angle of SE, respectively. The biggest advantage of FD detector is that we can easily trace the trajectories of the secondary electros. Fig. 1 shows the photograph of prototype FD. The subtraction of the images taken different bias voltages gives the energy filtered images. Using this detector, we have characterized various semiconducting materials. In this presentation we demonstrate the observations of surface potential variation of GaN islands on Si substrate and p-n junction of SiC wafer.

Microstructure and Corrosion Properties Investigations of AlCrNiCuMn High-Entropy Alloy

Using new high entropy alloy with chemical formula AlCrNiCuMn produced by high technology (induction melt method), in manufacture of new composite materials will enable the creation of new structures resistant to stress used dynamic collective protection. Specify that High Entropy Alloys are characterized as alloys consisting of approximate equal concentrations of at least five metallic elements and are claimed to favor close-packed, disordered structures due to high configurational entropy. In this study, we investigate the microstructure and corrosion properties of AlCrNiCuMn high-entropy alloys. The type of high entropy alloys manufactured was a five-component alloy of AlCrNiCuMn. The microstructure and corrosion resistance property of high-entropy alloys AlCrNiCuMn were determined by scanning electron microscopy and electrochemical workstation. Microstructural characterization was performed by electron microscopy on LMHII VegaTescan equipment using a secondary electron detector (SE) at a voltage of 30 kV electron gun.

Advanced Microscopic Study of Suspension Plasma-Sprayed Zirconia Coatings with Different Microstructures

The present paper is focused on the characterization of the differences between two microstructures that can be obtained using SPS technology, namely (i) columnar and (ii) two-zone microstructure including lamellas and fine unmelted particulates. The optimization of spray parameters was made, and the advanced microstructural studies of obtained coatings were performed. The work was focused on zirconia stabilized by yttria (YSZ, ZrO2 + 14 wt.% Y2O3) and both by yttria and ceria (YCSZ, ZrO2 + 24 wt.% CeO2 + 2.5 wt.% Y2O3) which are frequently used as thermal barrier coatings. Two types of microstructure were achieved using two different plasma torches, namely SG-100 of Praxair and Triplex of Oerlikon Metco. The microstructure of prepared coatings was analyzed using scanning electron microscopy with secondary electrons detector and backscattered electrons. Energy dispersive spectroscopy was performed to analyze the chemical composition of sprayed coatings. By electron backscatter diffraction grain shape, size, and crystal orientation were determined. The analysis enabled the discussion of the coatings growth mechanism. Finally, the Shape From Shading technique was applied to recreate and to analyze 3D views of coatings’ topographies, and using laser confocal microscopy, the surface roughness was examined.

Primeira ocorrência de zirconolita na Província Alcalina do Sul do da Bahia: intrusão sienítica do Complexo Alcalino Floresta Azul, Bahia, NE Brasil

Cristais de zirconolita (CaZrTi2O7) anédricos e subédricos, e com tamanhos inferiores a 20 μm foram identificados pela primeira vez na Província Alcalina do Sul do Estado da Bahia em sienitos do Complexo Alcalino Floresta Azul. Nesse estudo utilizou-se um microscópio eletrônico de varredura com detectores de elétrons secundários, elétrons retroespalhados e espectrômetro de energia dispersiva. A zirconolita é magmática e ocorre inclusa em oligoclásio antipertítico e microclina pertítica, estando usualmente em associação com baddeleíta, thorianita, zircão, monazita, esfalerita, pirita e ilmenita. Os dados químicos obtidos para os cristais de zirconolita estudados revelaram que eles são homogêneos e suas composições semelhantes àquelas descritas na literatura para zirconolitas de foid-sienitos e carbonatitos.

Secondary electron imaging of monolayer materials inside a transmission electron microscope

A scanning transmission electron microscope equipped with a backscattered and secondary electron detector is shown capable to image graphene and hexagonal boron nitride monolayers. Secondary electron contrasts of the two lightest monolayer materials are clearly distinguished from the vacuum level. A signal difference between these two materials is attributed to electronic structure differences, which will influence the escape probabilities of the secondary electrons. Our results show that the secondary electron signal can be used to distinguish between the electronic structures of materials with atomic layer sensitivity, enhancing its applicability as a complementary signal in the analytical microscope.

Scanning EM of non-heavy metal stained biosamples: Large-field of view, high contrast and highly efficient immunolabeling

Scanning electron microscopy (SEM) is increasing its application in life sciences for electron density measurements of ultrathin sections. These are traditionally analyzed with transmission electron microscopy (TEM); by most labs, SEM analysis still is associated with surface imaging only. Here we report several advantages of SEM for thin sections over TEM, both for structural inspection, as well as analyzing immuno-targeted labels such as quantum dots (QDs) and gold, where we find that QD-labeling is ten times more efficient than gold-labeling. Furthermore, we find that omitting post-staining with uranyl and lead leads to QDs readily detectable over the ultrastructure, but under these conditions ultrastructural contrast was even almost invisible in TEM examination. Importantly, imaging in SEM with STEM detection leads to both outstanding QDs and ultrastructural contrast. STEM imaging is superior over back-scattered electron imaging of these non-contrasted samples, whereas secondary electron detection cannot be used at all. We conclude that examination of ultrathin sections by SEM, which may be immunolabeled with QDs, will allow rapid and straightforward analysis of large fields with more efficient labeling than can be achieved with immunogold. The large fields of view routinely achieved with SEM, but not with TEM, allows straightforward raw data sharing using virtual microscopy, also known as nanotomy when this concerns EM data in the life sciences.

Low-pass secondary electron detector for outlens scanning electron microscopy

A low-pass secondary electron detector has been invented for outlens scanning electron microscopy. This detector is composed of a bias grid above and an electron detector below the specimen. The upward low-energy electrons emitted from the specimen are reflected downward by the bias grid and reach the secondary electron detector. The high-energy electrons penetrate the grid and are not detected. This detector has an advantage of quantitative analysis because the secondary electron trajectories are easily traced with simple parabolic motion. The energy-filtered images of the GaN/Si sample are obtained using this detector.

Virtual scanning electron microscope. 5. Application in nanotechnology and in micro- and nanoelectronics

The provided examples demonstrate the application of a simulator-based virtual scanning electron microscope (SEM) in certification of test object sizes on a low-voltage SEM and in calibration of a high-voltage SEM operating in the slow secondary electron detection mode. Using the virtual SEM, the problem of comparing different SEM calibration techniques is solved.

Properties of Ion–Electron Emission from the Surface of Semiconductor Material During Reactive Ion–Beam Etching

The existing methods of diagnosis of solid surfaces in ion − plasma processes have been analyzed. We found that the most efficient method of estimating surface condition, determining the transition of the etching process from one layer to another and determining the end of the etching process is the registration of ion − electronic emission during ion − beam etching. Results on secondary electron current for ion beam etching of various semiconductors have been reported. We show the experimental setup and describe the electric circuit for the detection of secondary electrons. An experimental study has been carried out to determine the dependence of secondary electron current on the band gap E g and the height of the potential barrier (electron affinity) χ of Ge, Si, GaAs, GaP and SiC semiconductor materials. We found no clearly expressed dependence of integral signal of ion − electronic emission on E g and χ . We show that under the conditions of ion beam etching under the influence of the surface potential the electric field penetrates in the semiconductor volume, leading to a shift in the energy levels of electrons in the surface layer and a change in the secondary electron current due to the appearance of autoelectronic emission. We found that the signal of ion − electronic emission in n − type silicon is higher than in p − type silicon. A model of ion − electronic emission from the surface of semiconductors is presented for the conditions of ion − beam etching, consisting of: emission with the participation of conductivity band electrons, emission due to the direct transition of electrons in the ion – atom system, and autoelectronic emission under the influence of surface potential.

Orientation contrast of secondary electron images from electropolished metals

Orientation contrast obtained by an in-lens secondary electron detector in a scanning electron microscope from electropolished/etched metals is reported. The imaging conditions for obtaining such orientation contrast are defined. The mechanism responsible for the formation of the orientation contrast is explained, and an application example of this new imaging method is given.

Sub-nanometre resolution imaging of polymer-fullerene photovoltaic blends using energy-filtered scanning electron microscopy.

The resolution capability of the scanning electron microscope has increased immensely in recent years, and is now within the sub-nanometre range, at least for inorganic materials. An equivalent advance has not yet been achieved for imaging the morphologies of nanostructured organic materials, such as organic photovoltaic blends. Here we show that energy-selective secondary electron detection can be used to obtain high-contrast, material-specific images of an organic photovoltaic blend. We also find that we can differentiate mixed phases from pure material phases in our data. The lateral resolution demonstrated is twice that previously reported from secondary electron imaging. Our results suggest that our energy-filtered scanning electron microscopy approach will be able to make major inroads into the understanding of complex, nano-structured organic materials.

A Fast Readout Electronic System for Accurate Spatial Detection in Ion Beam Tracking for the Next Generation of Particle Accelerators

This paper presents the design, implementation, and measurements of a complete electronic frontend intended for high-resolution spatial detection of ion beams at counting rates higher than $10^6$ particles per second (p/s). The readout system is made up of three main multichannel building blocks, namely, a transimpedance preamplifier, a signal-conditioning line receiver, and a charge-to-digital converter, as well as some off-the-shelf components. The preamplifier and the line receiver have been specifically designed and optimized to minimize the overlapping probability of ion beams tracking, at high counting rates, in low-pressure gaseous secondary electron detectors. Experimental results are shown, considering $\alpha $ particles sources and particles beams, featuring an adaptive shaping time frame of 170–230 ns with a peak signal-to-noise ratio of up to 25 dB. These performance metrics are competitive with the state of the art, demonstrating the suitability of the reported data acquisition and instrumentation system for precise and fast particle tracking detection.

Improvement of depth resolution and detection efficiency by control of secondary-electrons in single-event three-dimensional time-of-flight Rutherford backscattering spectrometry

An improvement of a depth resolution and a detection efficiency in single-event three-dimensional time-of-flight (TOF) Rutherford backscattering spectrometry (RBS) is discussed on both simulation and experiment by control of secondary electron trajectories using sample bias voltage. The secondary electron, used for a start signal in single-event TOF-RBS, flies more directly to a secondary electron detector with the positive sample bias voltage of several tens of volt than that without sample bias voltage in the simulation. The simulated collection efficiency of the secondary electrons also increases with the positive sample bias voltage of several tens of volt. These simulation results indicate the possibility of a smaller depth resolution and a shorter measurement time in single-event TOF-RBS with positive sample bias voltage. The measurement time for the Pt-stripe sample using single-event three-dimensional TOF-RBS with the sample bias voltage of +100V is 65% shorter than that without sample bias voltage, resulting in a less sample damage by a probe beam. The depth resolution for the Pt stripes under the 50-nm-thick SiO2 cover-layer with the sample bias voltage of +100V is 4nm smaller than that without sample bias voltage. Positive sample bias voltage improves the depth resolution and the detection efficiency in single-event three-dimensional TOF-RBS without an influence on the beam focusing.

Changes in Mechanical Properties of Rat Bones under Simulated Effects of Microgravity and Radiation†

The aim of this study was to determine the changes in elasticity and lattice structure in leg bone of rats which were: 1) under Hind-Limb Suspension (HLS) by tail for 2 weeks and 2) exposed to a total radiation of 10 Grays in 10 days. The animals were sacrificed at the end of 2 weeks and the leg bones were surgically removed, cleaned and fixed with a buffered solution. The mechanical strength of the bone (elastic modulus) was determined from measurement of bending of a bone when under an applied force. Two methodologies were used: i) a 3-point bending technique and ii) classical bending where bending is accomplished keeping one end fixed. Three point bending method used a captive actuator controlled by a programmable IDEA drive. This allowed incremental steps of 0.047mm for which the force is measured. The data is used to calculate the stress and the strain. In the second method a mirror attached to the free end of the bone allowed a reflected laser beam spot to be tracked. This provided the displacement measurement as stress levels changed. Analysis of stress vs. strain graph together with solution of Euler-Bernoulli equation for a cantilever beam allowed determination of the elastic modulus of the leg bone for (i) control samples, (ii) HLS samples and (iii) HLS samples with radiation effects. To ascertain changes in the bone lattice structure, the bones were cross-sectioned and imaged with a 20 keV beam of electrons in a Scanning Electron Microscope (SEM). A backscattered detector and a secondary electron detector in the SEM provided the images from well-defined parts of the leg bones. Elemental compositions in combination with mechanical properties (elastic modulus and lattice structure) changes indicated weakening of the bones under space-like conditions of microgravity and radiation.

Energy filtration of secondary and backscattered electrons by the method of the retarding potential in scanning electron and ion microscopy

Data for the study of various contrasts in the methods of scanning electron and ion microscopy with the energy filtration of signals from secondary and reflected electrons are presented. A model of the formation of contrast by secondary electrons in a helium scanning electron microscope is formulated. The possibility of contrast amplification via energy filtration in a helium ion microscope as well as the chance of recording reflected ions by means of secondary electron detection is demonstrated. The recorded data for the material contrast in low-voltage electron microscopy at various acceleration voltages and different modes of energy filtration are given. The possibility of enhancing or reducing material contrast by means of energy filtration is shown.

Multi-scale characterization by FIB-SEM/TEM/3DAP

In order to improve properties of functional materials, it is important to understand the relation between the structure and the properties since the structure has large effect to the properties. This can be done by using multi-scale microstructure analysis from macro-scale to nano and atomic scale. Scanning electron microscope (SEM) equipped with focused ion beam (FIB), transmission electron microscope (TEM) and 3D atom probe (3DAP) are complementary analysis tools making it possible to know the structure and the chemistry from micron to atomic resolution. SEM gives us overall microstructural and chemical information by various kinds of detectors such as secondary electron, backscattered electron, EDS and EBSD detectors. Also, it is possible to analyze 3D structure and chemistry via FIB serial sectioning. In addition, using TEM we can focus on desired region to get more complementary information from HRTEM/STEM/Lorentz images, SAED/NBD patterns and EDS/EELS to see the detail micro or nano-structure and chemistry. Especially, combination of probe Cs corrector and split EDS detectors with large detector size enable us to analyze the atomic scale elemental distribution. Furthermore, if the specimen has a complicated 3D nanostructure, or we need to analyze light elements such as hydrogen, lithium or boron, 3DAP can be used as the only technique which can visualize and analyze distribution of all constituent atoms of our materials within a few hundreds nm area. Hence, site-specific sample preparation using FIB/SEM is necessary to get desired information from region of interest. Therefore, this complementary analysis combination works very well to understand the detail of materials.In this presentation, we will show the analysis results obtained from some of functional materials by Carl Zeiss CrossBeam 1540EsB FIB/SEM, FEI Tecnai G(2) F30, Titan G2 80-200 TEMs and locally build laser assisted 3DAP. As the one of the example, result of multi-scale characterization for ultra-fine grain Nd-Fe-B permanent magnet will be shown [1]. In order to improve the magnetic properties, especially to increase the coercivity (resistance against magnetization reversal) of the magnet, decreasing the grain size and isolating each grain by non-ferromagnetic grain boundary phase are quite important since the nucleation of magnetic reversal from grain boundary phase can be suppressed and pinning force of magnetic domain wall at the grain boundary phase can be strengthened. Therefore, micro and nano structure and chemistry analysis can shed a light do grain boundary engineering.Figure1(a,b) shows SEM BSE images of ultrafine grain Nd-Fe-B sintered magnet and the reconstructed 3D tomography of Nd-rich phases obtained by FIB/SEM serial sectioning. This data can provide us information about the distribution of Nd-rich phase and its volume fraction. Moreover, the HRTEM image from the grain boundary phase, the 3DAP maps and the concentration depth profiles are shown in Fig.1(c,d,e). This magnet shows high coercivity (1517kA/m), and by comparing these results with the microstructures of low coercivity specimen, importance of grain boundary formation was confirmed and it gives us hint to improve the coercivity further. We will show the detail and results from other materials.jmicro;63/suppl_1/i6/DFU046F1F1DFU046F1Fig. 1.(a) SEM BSE images of ultrafine grain Nd-Fe-B sintered magnet. (b) 3D FIB/SEM tomography of Nd-rich phases. (c) HRTEM image from the grain boundary phase. (d) 3DAP maps of Nd, Cu and Al. (e) Concentration depth profiles for Fe, Nd+Pr, B, Co, Cu and Al, determined from the selected box in (d)[1].

High Energy BSE/SE/STEM Imaging of 8 um Thick Semiconductor Interconnects

High energy (100-400 keV) scanning electron microscope (SEM) imaging of samples can be performed in the transmission electron microscope (TEM)/scanning TEM (STEM) when the system has secondary electron (SE) and/or backscattered (BSE) electron detector(s) installed. Previously, very high resolution SE imaging has been demonstrated at 200 keV in a STEM with a spherical aberration corrected condenser lens [1]. Additionally, imaging of semiconductor Cu interconnects in SiO2 dielectric located at distances > 3um below the surface has been accomplished using incident beam energies of 100-400 keV and a backscattered electron (BSE) detector [2]. In the high energy BSE analysis case, multilevel Cu interconnects are ideal structures to study because: 1) there is a large BSE yield difference between Cu and SiO2 so Cu can be easily detected and 2) Cu lines exist at multiple levels below the surface so multiple structures can be seen from different depths in one BSE image. In this paper, a semiconductor chip with 9 interconnect levels spanning 8 um in height was studied using SE, BSE and STEM imaging at incident beam energies of 300-400 keV in order to understand image content and quality versus the depth of the structure below the surface.