bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Specimen Bias on the Contrast of High Resolution Low Voltage SEM Images in a Semi-In-Lens JSM-6320f Fe-SEM
Authors: J.Liu
Published: July 2020

Nanometer-resolution surface imaging by secondary electrons (SE) is now routinely obtainable in field-emission SEM or STEM microscopes. The resolution in SE images obtained in a modern field-emission (FE) SEM is still limited by the electron probe size although the localization of the SE generation processes sets the ultimate resolution limit that will be achievable in SE images. The combination of a FE gun with improved probe forming lenses and detection systems makes it possible to image nanometer-scale surface features at low voltages. Because of the reduced electron beam range and the new SE detection system, image contrast formation in low voltage FE-SEMs is quite different to that in conventional SEMs. In a FE-SEM, SEs are detected through the combination of a strong magnetic field of the lens and a weak electrostatic extraction field of the detector. The detection efficiency varies with the energy of the emitted SEs.
Image Reconstruction in Atomic Force Microscopy
Authors: Goh M Cynthia
Published: July 2020

The atomic force microscope has been an essential tool in the past few years for visualization of mesoscopic structures, and has been applied to numerous examples in biological systems. The finite size of the probe tip, however, means that the picture produced by the AFM inevitably includes the tip geometry convoluted with the desired image of the sample. If the tip is asymmetric and/or deformed, the resulting image may bear little resemblance to the original sample. Even in the case of a “good tip”, however, the effect on the image is non-negligible, causing broadening and obscuring of features. In this presentation, approaches developed in our laboratory with regards to problems in imaging mesoscopic samples will be discussed.

In samples where the primary tip-sample interaction is via excluded volume - that is, the tip and sample are mutually impenetrable and come into contact - we had been utilizing a numerical algorithm for removing the tip geometry from the AFM image.
Topography of Nacre/Prismatic Growth Edge in Red Abalone by AFM
Authors: Graham Thomas , Sarikaya Mehmet
Published: July 2020

Formation and growth mechanisms of biological hard tissues are relevant in biomimetics for obtaining lessons in the assembly of complex and ordered microstructures for engineering applications. Shells of mollusks offer examples of organic/inorganic hybrid structures with nanoscale order that produce functionally-gradient macroarchitectures. Here, the nacre/prismatic interface of red abalone (Haliotis rufescens) was topographically profiled with an atomic force microscope (Park Scientific PC) using contact mode in air to elucidate growth characteristics of the shell. The results give a quantitative (spatial and temporal) measure of how nacre (N) grows over the prismatic (P) section of the shell.

Nine regions, with a length of 350 µm parallel to the growing edge and a width of 120 µm, were scanned (e.g., Figs 1 & 2). Raster scanning from N to the P sections revealed that the rms roughness of the surface tends to increase from N to P region with the latter having topographical height variations of up to 5 µm at the growing edge.
Scanning Probe Microscopy: Internet Resource Development and Integration into Undergraduate Curriculum
Authors: Kline RJ , Leonard DN , Batchelor AD , Russell PE
Published: July 2020

The Internet has become a very valuable educational resource. It allows a person to be able to reach a very large, diverse audience across the world with ease. With NSF Combined Research-Curriculum Development (CRCD) funding, we have begun to use the Internet as an educational and technical resource for people wanting to learn about Scanning Probe Microscopy (SPM). We have set up a web page with informative information for people of all levels of SPM knowledge. We are actively combining SPM research and education into the materials science and engineering undergraduate curriculum. We also use the web page as a way to publish our findings to help other universities integrate SPM into their curriculums.

The URL is: http://spm.aif.ncsu.edu

The web page is divided into seven main components. Each component has a specific intended audience and purpose. We have designed some components for people who have never heard of SPM and others for people who run SPM labs.
Scanning Electron Microscopy And Electron Probe Microanalysis Of Extraterrestrial Materials
Authors: Goldstein J I
Published: July 2020

One of the first samples analyzed by Castaing in his electron probe microanalyzer (EPMA) some 50 years ago was an iron meteorite. The Widmanstatten pattern microstructure of iron meteorites can be observed at very low magnifications ( Fig. 1). These meteorites are ideal samples for microanalysis because of the Ni gradient which extends over 10 to 1000 microns in the parent taenite phase of these Fe-Ni samples (Fig. 3). The Ni gradient is the result of very slow cooling of the iron meteorite, in terms of millions of years, within a parent'asteroid.

The scanning electron microscope (SEM) has been used to characterize the microstructure of meteorites, as well as samples from the moon and mars. For example, the microstructure of the dark etching taenite areas (T in Fig. 1) of the Carleton iron meteorite is shown in Fig 2. In this example, precipitates are observed along original martensite laths which form during the cooling of the iron meteorite at low temperatures.
The Nc State Analytical Instrumentation Facility
Authors: Phillips JR , Griffis DP , Russell PE
Published: July 2020

The Analytical Instrumentation Facility (AIF) is a laboratory composed of scientists and engineers specializing in the development and application of advanced techniques for materials characterization (http://spm.aif.ncsu.edu/aif/index.html)http://www.nice.org.uk/page.aspx?o=43210. AIF facilities include an extensive collection of analytical instrumentation utilized in teaching, research, and in support of academic and industrial programs. General forms of analysis include: electron, ion, and photon microscopies, surface science and analysis, and scanned probe microscopies. An abbreviated listing of AIF capabilities follows: metallography/sample preparation, optical microscopy, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Secondary Ion Mass Spectroscopy (SIMS), Secondary Electron Microscopy (SEM), Scanned Probe Microscopy (SPM), Micro-Raman Spectroscopy, Focused Ion Beam Micro-machining (FIBM), Auger Electron Spectroscopy (AES), and X-Ray Photoelectron Spectroscopy (XPS or ESCA).

AIF is a resource utilized not only by those within NC State requiring analytical services, but also by a large number of North Carolina non-profit and industrial organizations as well as the Materials Community at large.
Olis: On-Line Image Simulation And Structure Characterization For The Materials Microcharacterization Collaboratory
Authors: O'Keefe Michael A , Taylor John R
Published: July 2020

The Materials Microcharacterization Collaboratory (MMC), a pilot project of the DOE2000 program, links DOE-sponsored electron microscope user facilities at ANL, LBNL, ORNL and UIUC with that at NIST to form one collaboratory. The MMC brings the microcharacterization and microanalysis tools available in these national centers to geographically-dispersed researchers working in industries,universities, and government laboratories. It enables remote users to share on-line the instrumentation, knowledge and expertise available at the individual facilities making up the collaboratory.

On-line services available to users of the MMC may be classified as instrument, computational, and exchange services (fig. 1). LBNL's contribution to the MMC's instrumentation includes a Kratos EM-1500 HVEM (for remote in-situ high-voltage microscopy) and a Philips CM300 HREM (remote highresolution capability). DeepView is an exchange service that provides a common graphical userinterface (GUI) for control of MMC instruments over the wide area network (both the client and server sides of DeepView are available for download).
Switching Behaviour of Sub-Micron Magnetic Elements Studied By Tem
Authors: Chapman J N , Kirk K J , Herrmann M , McVitie S , Scheinfein M R
Published: July 2020

Magnetic elements in the micron and sub-micron size range are important for application as discrete bits in high density storage systems and as the active part of ultra-small magnetic sensors of the kind required in read heads. Patterning techniques based around electron beam lithography are used to fabricate elements with different sizes and shapes and TEM allows the magnetisation distributions they support to be investigated. Figure 1 shows a regular domain structure in a rectangular element of length 1μm. Of particular importance is the ability to observe directly how the elements respond to an applied field and thereby to gain information on magnetisation processes. When the fields required are in excess of a few 100 Oe, it is most convenient to use the vertical field of the objective lens. Field components in the specimen plane are then generated by tilting. For this technique to be effective it must be possible to choose an objective field strength appropriate to the elements under study and to have separate non-immersion lenses (Lorentz lenses) as the primary imaging or probeforming components.
Quantitative Electron Holography Of Magnetic Materials
Authors: McCartney M R
Published: July 2020

Off-axis electron holography is a powerful method for providing quantitative micromagnetic structure to nanometer-scale resolution. One of the main challenges in determining magnetic induction from reconstructed phase images is the separation of phase shifts due to electrostatic and thickness effects from magnetostatic effects. We have used in-situ magnetization reversal to remove electrostatic and thickness effects which would otherwise prevent quantification of the induction. The Philips CM200-FEG microscope which was used for the holography described here is equipped with a powerful mini-lens below the specimen enabling 2nm spatial resolution (∼5nm phase resolution) and only a small residual field at the sample. In addition, the objective lens field versus current has been calibrated so that external vertical fields over a wide range of values may be applied to the sample. Tilting the sample in the presence of the vertical field has the effect of ‘applying an inplane component. This combination of high spatial resolution, quantitative analysis and in situ capabilities allows for the study of individual defects and provides experimental input for comparison with simulations.
Raman Microscopy As A New Failure Analysis Tool In The Thermal Inkjet Cartridge Industry
Authors: Hammond Loma
Published: July 2020

In order to remain competitive in the rapidly growing inkjet printer industry, higher and higher demands are being made on print speed and print/image quality. As a result, the critical dimensions of thermal inkjet cartridge printheads are being constantly reduced in order to yield smaller ink droplets at higher frequencies. In order to enhance our laboratory’s ability to acquire vibrational spectral data from the increasingly small sample sizes encountered in failure analysis problems, a Raman microscope was recently added to our infrared microscopy laboratory.

The addition of a Raman microscope has increased our analysis capabilities in several ways. While infrared microscopy is diffraction limited at 10 μm, Raman microscopy can be used to study spot sizes as small as 1 μm in diameter. This has greatly expanded the range of particles which can be identified in our work. The Raman spectrum acquired of an adhesive particle in a printhead bore is shown in Fig.1.
Structure And Composition Of Grain Boundaries In SrTiO3
Authors: Kienzle O , Ernst F , Rühle Manfred
Published: July 2020

The electrical properties of SrTiO3 (strontium titanate) ceramics are strongly influenced or even dictated by grain boundary segregation of charged point defects, such as dopant atoms, impurities, vacancies, or self-interstitials. The atomistic structure of the grain boundaries, their energy, and the segregation of point defects mutually depend on each other. Grain boundary segregation of charged point defects induces the formation of space charge layers in the adjoining crystals. In order to investigate the relation between grain boundary structure and composition, grain boundaries in Fedoped SrTiO3 bicrystals and in SrTiO3 ceramics were studied by HRTEM and by AEM with subnanometer resolution.

Quantitative HRTEM served to investigate the atomistic structure of Σ=3, (111) grain boundaries in Fe-doped SrTiO3 bicrystals with a doping level of Fe/Ti= 0.04at% (Fig. 1). Analysis of the translation state revealed that the Σ=3, (111) grain boundary has an excess volume: normal to the boundary plane, the spacing between the two crystals exceeds what one would expect from a coincidence site lattice model by (0.06 ±0.01 )nm.
Interfaces In Glass-Containing Ceramics
Authors: Barry Carter C , Ravishankar N , Korte Carsten , Mallamaci MP
Published: July 2020

The interaction of a liquid with a solid substrate has been the subject of intense research since the early 1800s. The subject is relevant and very important even today from a basic science as well as technological standpoint. Liquid-phase-sintered oxide ceramics often contain a siliceous glassy layer in the grain boundaries which affect the properties of the ceramic. The wetting of the grain boundaries by the liquid has a strong dependence on the crystallography. While some boundaries are preferably wet, other special boundaries appear to be completely ‘dry’. The presence of the liquid film also affects the faceting behavior of the boundary plane. While several studies have been carried out on these intergranular glass films, many of the basic issues still remain unclear. The development of modern microscopy techniques facilitate the characterization of structure and chemistry at a high spatial resolution. This paper deals with the microstructural examination of two of the important issues involved with these intergranular films, i.e., faceting of grain boundaries in the presence of a glassy phase and the behavior of interfaces between two glassy phases of different compositions.
Mapping The Valence States of Transition Metals Across Interfaces By Energy-Filtered Tem
Authors: Wang ZL , Bentle J , Evans ND
Published: July 2020

Some properties of transition metal oxides are related to the presence of elements with mixed valences. In electron energy-loss spectroscopy (EELS), the L or M ionization edges of transition-metal, rare-earth and actinide elements usually display sharp threshold peaks known as white-lines. EELS experiments have shown that a change in cation valence state introduces a significant change in the White-line intensity ratio [1]. With the use of valence state information provided by the white lines, an experimental approach is demonstrated here to map the valence state distributions of Mn and Co using an energy-filtered transmission electron microscope (TEM). A spatial resolution of ˜ 2 nm has been achieved. This technique should be particularly useful in studying valence states of cations in magnetic oxides.

To map the distribution of ionization states, an energy window of ˜ 10 eV in width is required to isolate the L3 from L2 white lines (Figure 1).
Characterization Of Bonding At The Ni-Sio2 Interface Using Electron Energy-Loss Spectrometry
Authors: Taylor S T , Gronsky R
Published: July 2020

Changes in electronic structure and bonding at metal-oxide interfaces can have a pronounced influence on the macroscopic properties of the interface. This is particularly true for supported-metal catalysts, which feature nanometer-sized transition metal particles dispersed on an inert support such as A12O3 or SiO2. Variations in the d-band filling of the transition metal due to chemical bonding with the support could potentially alter the chemical activity of metal atoms near the interface, thereby affecting catalyst performance. This work investigates possible interface contributions to the performance of a model Ni- SiO2 catalyst system by directly assessing the nature of bonding at the metal-oxide interface. Electron energy-loss spectrometry (EELS) in the TEM is used to examine and quantify changes in the d-band occupancy of interfacial Ni atoms relative to the bulk, and to further relate these changes to interface chemistry.

The Ni d-band occupancy is evaluated using the integrated area under the Ni L2,3 edge in the energyloss spectrum, according to routines establishe-i previously.
Tem Investigation Of Precipitate Shapes And New Interface Phenomena In Al-Pb Alloys
Authors: Dahmen U , Johnson E
Published: July 2020

Transmission electron microscopy plays a key role in the investigation of precipitates and inclusions because it provides direct information at high spatial resolution, on their shape, orientation relationship, interface structure and composition.

This work has utilized high resolution and in-situ electron microscopy to study the equilibrium shapes and thermal behavior of Pb precipitates in Al. It was found that PB precipitates within Al grains form in parallel-cube orientation relationship, are cuboctahedral in shape, adopt a sequence of magic sizes, and display an increase in aspect ratio with decreasing size. These observations have been explained in terms of interfacial energy and residual strain energy.

When the same Pb precipitates form on grain boundaries, their shapes are significantly different. This is apparent from figure 1 which shows a 90° <110> tilt grain boundary in Al with a small cuboctahedral Pb precipitate in the upper grain and a large complex-shaped Pb particle on the grain boundary.
Dynamic Interfaces In Carbon Nanostructures
Authors: Ajayan P M , Banhart F
Published: July 2020

Carbon nanotubes and carbon onions are two fascinating forms of crystalline nanosize carbons that have received considerable attention in recent years (1,2). The remarkable physical properties of nanotubes make them valuable material for applications ranging from electronic devices to nanoprobes. The dimensions and topology of these structures make them fascinating objects for study. Multiwalled nanotubes and onions are made of concentric graphite layers, with different geometry. Singlewalled nanotubes on the other hand are made of singular graphene cylinders, often self-assembled into larger rope-like structures. Nanotubes can be produced in gram quantities using electric arc or laser ablation. Carbon onions, however, are structures that assemble from carbonaceous soot under intense electron irradiation in an electron microscope. Hence the onions are metastable structures that become unstable and disintegrate in the absence of irradiation.

The multiwalled carbon nanotubes and carbon onions have been shown to encapsulate foreign materials (metals, oxides, carbides), either during growth or by capillarity filling (in the case of nanotubes) (1), or during irradiation of metal containing soot (onions) (3).
Composition Distribution In Laterally Modulated Inalas Films
Authors: Twesten RD , Follstaedt D M , Mirecki Millunchick J , Lee S R , Norman AG , Arenkiel SP , Reno J L , Jones E D , Mascarenhas A , Zhang Y
Published: July 2020

Quantum confinement effects in opto-electronic materials have typically been limited to onedimensional confinement due to the constraints of epitaxial growth techniques. One method of forming higher degrees of confinement is the spontaneous lateral modulation seen in InAlAs shortperiod superlattices (SPS) grown on InP(00l). Here, a small number of monolayers (0.5 ˜ 2) of InAs and AlAs is alternately deposited by MBE to build a layer that exhibits lateral modulation on the 10 ˜ 25 nm scale. These materials show strong polarization and a large red shift (˜500meV) of the photo-emission spectra.

A key to understanding and predicting the properties of these films is determining their composition distribution. Using an HB-501 STEM, we have investigated the detailed composition distribution within a strongly modulated sample. The sample was grown in slight tension with respect to the InP substrate, a condition in which lateral modulation is known to be strong. Figure 1 shows a highangle annular dark-field (HAADF) image together with an intensity line scan from the image.
The 3d Parameters Of A (Nano)Crystal From Lattice Images At Two Tilts
Authors: Qin Wentao , Siriwardane Haresh , Fraundorf Phil
Published: July 2020

Various techniques have been developed to infer the 3D relationship of reciprocal lattice vectors from electron diffraction patterns taken at different specimen orientations. Such relationship is subsequently applied in crystallographic analyses. Due to the transmitted nature of the electron beam, TEM images present 3D information averaged throughout the thickness of the specimen on each micrograph. Techniques for acquiring 3D information from such images include stereomicroscopy for characterizing irregular dislocation networks, and 3D reconstruction of nonperiodic macromolecular assemblies. Prospects for finding the 3D lattice parameters of nanocrystals from HREM images taken at different specimen orientations have been discussed. Here we apply this stereo lattice imaging to a 7 nm crystal, and discuss its application to compact fee and bec lattices in general. Results on other lattice types will be published separately.

Generally 3 non-coplanar lattice vectors seen along 2 different zone axes are sufficient for inferring a subset of the 3D reciprocal lattice of a single crystal.
Electron Spectroscopic Imaging (ESI) of Viral DNA- and RNA-Distribution Using a New Method of Background Subtraction
Authors: C.Crucifix  , Witz J , Schultz P , Pawlita M , Trendelenburg M F , Probst W , Haking A , Troester H
Published: July 2020

Our investigations are aimed to exploit the potential of Electron Spectroscopic Imaging (ESI) using an LEO EM 912 Omega to perform element detection without any background signal included in the net elemental signal. In a first series of experiments we designed an approach for phosphorus (P) detection by using an internal mass-thickness marker in the shape of a carbon ramp combined with the two-window difference method in order to eliminate mass thickness signals [1]. However, pure carbon seems not to be ideal because this approach does not take into account the more complex elemental composition of biological samples ( H, N, O, P and S) compared to pure carbon within the reference. Consequently, we had to find an easy-to-handle and reproducible technique to include a combined Compositional- and Massthickness Marker (C:M-Marker) in the specimen under investigation. Fig. 1A shows the result of such an experiment. Turnip Yellow Mosaic Viruses (TYMV; bright particles) were layered on top of a carbon foil followed by a wash with distilled water and air drying. To form an internal C-M-Marker a 1%-solution of Bovine Serum Albumin (BSA), dialysed against H2O, was sprayed on the opposite side of the same sample resulting in localized aggregations of BSA with different thicknesses (bright region “M, Fig. 1A). It serves the same purpose like the carbon ramp [1]: a pre-edge image (115 eV) and a second one (150 eV, core edge image) are taken to calculate the intensity (I) background function I150 (I115) using only values from the C-M-Marker region. Then the P-map image can be calculated by subtracting the extrapolated contribution of the protein part from the core-edge image. For the case presented in Fig. 1A this procedure resulted in Fig. 1B where the TYMV intensity signals can still be seen whereas the BSA ramp vanished.
Microtextural Characterization and Orientational Mapping of Polycrystalline Thin Films Using TEM Dark Field Imaging Through an Annular Objective Aperture
Authors: Williamson M , Hull R , Dunn D , Greene J , Kodambaka S
Published: July 2020

Several methods have been applied to the texture characterization of polycrystalline films, including X-ray diffraction and several SEM and TEM techniques. Few of these techniques combine high spatial resolution with the ability to characterize large sample areas in a short time. We have fabricated annular objective apertures for the TEM, extending earlier work of Heinemann and Poppa, to characterize the orientation and size of grains within polycrystalline thin films. This procedure is similar to conical dark field imaging which has been shown to provide microtextural information over large areas

Apertures were fabricated using a FEI FIB-200 focused ion beam (FIB) workstation. Bitmap templates of apertures were created using Adobe Illustrator™ and converted to stream files. These stream files were then used to controllably cut annular apertures into an existing platinum JEOL aperture strip with a 30 keV Ga+ FIB. The apertures were then placed in the objective aperture drive of a JEOL 2000FX transmission electron microscope and TiN thin films were imaged in bright- and dark-field imaging modes.
An Investigation of Plastic Strain in Copper by Automated-EBSP
Authors: Sutliff J A
Published: July 2020

This work describes the investigation of plastic strain in tensile deformed polycrystalline copper using the automated Electron BackScatter Pattern (EBSP) technique of electron diffraction in the Scanning Electron Microscope (SEM). A strong correlation was found between the known accumulated plastic strain in OFHC copper tensile specimens and quantitative measurements of intra-grain misorientation obtained from an analysis of automated-EBSP data.

Previous works on strain measurement using EBSP analysis have focused on the influence of dislocation density on the intensity profiles of diffraction bands. It is known that for some materials, like copper, deformation strain produces highly organized dislocation structures and thus the dislocation density is very inhomogeneous on the sub-micron scale probed by EBSP. This suggests that plastic strain analysis using the EBSP dislocation density analysis route will be difficult to reliably implement in these materials.
A Study on the Characteristics of the Boundaries in Bainitic Low Alloy Steels Using Electron Back-Scatter Diffraction (EBSD) Technique
Authors: Oh Yong-Jun , Kim Min-Chul , Hong Jun Hwa
Published: July 2020

Bainitic low alloy steel has a complex microstructure exhibiting several types of boundaries. The boundaries in bainitic steel, although certain boundaries are absent with respect to the alloy composition and the manufacturing process, could be typically divided into 4 types; dislocation cell boundary, lath boundary, packet boundary, and prior austenite grain boundary, in increasing order of size. The size and distribution of the respective boundaries are an important factor which controls the mechanical properties of the steels, including brittle fracture. In the present research, the characteristics of the boundaries in the bainitic low alloy steels were investigated in view of misorientation between grains enclosed by the respective boundaries.

The alloys investigated were Mn-Mo-Ni low alloy forging steels having chemical compositions shown in TABLE 1. Steel-A was manufactured by the Vacuum Carbon Deoxidation(VCD) process. For the finer prior austenite grain size, Steel-B was produced by the aluminium addition and the silicon killing process. Before EBSD analysis, the microstructures of the alloys were observed using SEM and TEM. EBSD measurements were obtained using a Link OPAL system(Oxford) linked to a JEOL JSM 6300 SEM operating at 15KeV with the sample tilted at 70°.
Epitaxial Orientation Determination of Nanosized Particles by EBSD
Authors: Cosandey F , Zhang L , Madey T E
Published: July 2020

Metals on oxide systems are important in applications such as catalysts and gas sensors. The Au/ TiO2 system is of particular interest because of its high activity for low temperature oxidation of CO and its good sensitivity as CO gas sensor. In this study, we are reporting results on the effect of substrate temperature on epitaxial orientation relationship of Au particles formed on TiO2 (110).

Two Au films were grown on TiO2 (110) substrates by vapor deposition in a UHV chamber. The first one was produced by evaporation of a 12nm thick Au film at 300K, followed by annealing at 775K for 1 hour. The second one was produced by direct deposition of a 12nm film on TiO2 substrate maintained at 775K. The samples were transferred in air to the Field Emission Scanning Electron microscope (LEO 982 Gemini) for imaging and diffraction..Electron Backscatter Diffraction (EBSD) patterns were taken from individual Au particles using the Opal system (Oxford Instruments). With this system, a spatial resolution of the order of 80 nm has been achieve for Au.

A typical HRSEM image of the Au film deposited a 300K and annealed at 775K is shown in Fig. 1 revealing a discontinuous Au film consisting of discrete Au particles in the range from 20 to 150 nm.
Review of Electron-Gas Interactions in the Environmental SEM
Authors: Thiel BL
Published: July 2020

Understanding the various interactions between electrons and the specimen chamber gas is essential to using environmental and low-vacuum SEM’s to their full potential. The problem can be divided into two main topics: distortion of the primary beam on its way to the sample surface, and amplification of the various electron signals leaving the sample. These issues are important for all low-vacuum SEM’s, regardless of the system design or signal detection method. All instruments must contend with scattering of the primary beam in the gas, and the subsequent effects on resolution, background signals,.and x-ray generation. Similarly, while some instrument designs rely more heavily than others on signal amplification in the gas, all benefit from the concomitant charge neutralisation.

As the electron probe travels through the gas on its way to the specimen, elastic collisions occur with molecules in the gas.[1] Fortunately, for gas pressures of a few torr, the mean free path is on the order of tens of millimetres, and the vast majority of electrons reach the specimen unscattered.
Contrast formation mechanisms in the environmental scanning electron microscope
Authors: Toth M , Phillips MR
Published: July 2020

Uncoated, non-conductive samples can be imaged and analyzed in the environmental scanning electron microscope (ESEM) due to effective charge neutralization at the sample surface by ionized gas molecules. Under some gas pressure and electron dose conditions, ESEM images of uncoated, poorly conductive samples often contain contrast not present in secondary or backscattered electron images of the (coated) samples obtained in conventional SEMs. It has been proposed that the contrast is related to charge trapping at defects and impurities. It has also been suggested that UV cathodoluminescence (CL) may contribute to contrast in the ESEM. In this paper, we present experimental evidence of contrast formation in the ESEM due to charge trapping in Dy doped zircon, electron trapping at oxygen vacancies in sapphire and the absence of signal generation by 360nm UV CL.

The specimens used in this study were (i) cross-sectioned Titanium in-diffusion doped sapphire single crystal, (ii) Dy doped synthetic Zircon7 and (iii) 43 μm epitaxial GaN grown on c-pane sapphire by hydride vapor phase epitaxy.
Secondary Electron Yield Curve for Liquid Water
Authors: Thiel BL , Stokes DJ , Phifer D
Published: July 2020

We have measured the secondary electron yield curve for liquid water using an Environmental SEM. The secondary electron emission coefficient, measured as a function of incident electron energy, is important for interpreting contrast in hydrated biological and inorganic specimens. This information is even more critical for water than other materials, as it is a factor of prime importance in understanding radiation damage in biological tissues.[1]

These measurements were taken using a Philips XL-30 field emission,ESEM, and repeated on an Electroscan E3 ESEM, equipped with a CeB6 filament. A specially designed Faraday cup was fashioned from brass and fitted with a removable graphite cup having an inset for a platinum aperture. This assembly was placed into an electrically floating Peltier cooling stage, and connected to a KE Instruments probe current meter.
ESEM Imaging of P-N Junctions Using a Gaseous Secondary Electron Detector
Authors: Phillips MR , Toth M , Drouin D
Published: July 2020

Contrast in secondary electron images of p-n junctions has been observed using a FESEM operating at 1kV. This contrast has been attributed to energy band-bending effects and dopant level variations. In this paper, we report that contrast from the depletion layer of a p-n junction can be obtained in an ESEM using a gaseous secondary electron detector (GSED). The contrast is caused by a signal induced in the GSED by charging and discharging of the device.

A 1N4002 p+pn silicon power diode was cross-sectioned along the lead axis to expose the Ag ohmic contacts and the semiconductor device. The section was mechanically polished to an optical finish using diamond abrasives and mounted in a holder which allowed electrical connection to both the p and n sides of the diode. Imaging experiments were performed in a Philips Electroscan XL30 ESEM and a JEOL 6300F below-lens FESEM. Current images were obtained with a GW Electronics 103 specimen current amplifier.
A Novel Technique for Probe Intensity Profile Characterisation in the Environmental Scanning Electron Microscope
Authors: Phillips MR , Toth M , Drouin D
Published: July 2020

The environmental scanning electron microscope (ESEM) allows imaging and analysis in a gaseous environment at pressures up to 20 torr. Gas phase scattering of primary electrons leads to a loss of useable probe current and produces an electron skirt around the beam that can degrade the spatial resolution in microanalytical studies. Progress in ESEM microanalysis requires accurate modeling and measurement of the beam intensity profile. Previously, x-ray techniques and beam sensitive materials have been used to measure the extent of the skirt. These investigations have yielded inconsistent skirt distances possibly due to dose dependence of the measurement techniques. We present a new, high gain method to measure the useable probe current and skirt profile using the electron beam induced current (EBIC) from a P-N junction.

The interface of an N- and a P-type semiconductor contains an electrostatic donor-acceptor dipole (“depletion layer”) created by an electron-hole recombination energy minimization mechanism.
Accuracy of Spatial Measurements at Elevated Temperatures in an Environmental Scanning Electron Microscope
Authors: Schalek Richard L , Drza Lawrence T
Published: July 2020

One of the unique abilities of the environmental scanning electron microscope is that it permits realtime dynamic observations of materials under controlled temperature/atmosphere conditions [1]. The need for accurate and precise measurements of dimensional changes at elevated temperatures arise in many material areas including determining the longitudinal and transverse coefficient of thermal expansion of fibers, sintering studies, hydration and dehydration of absorbent polymers, and strain measurement of materials under an applied load. The purpose of this research is to evaluate the capabilities of an ElectroScan 2020 environmental scanning electron microscope (ESEM™) in performing precise in situ spatial measurements at elevated temperatures. Identification and proposed solution and/or compensation of imaging difficulties such as specimen drift, sample stability, and thermal strain of a reference grid are addressed.

In general, the accuracy of spatial measurements in a scanning electron microscope (SEM) depends on several factors including calibration of the scanned area, the effects of lens hysteresis and reproducibility in the working distance and column alignment.
In Situ TEM Study of DNA/Gold Nanoparticles in Liquid Environment
Authors: Chiou W-A , Mucic R C , Ishikawa A , Konishi H , Fukushima K , Mirkin C A
Published: July 2020

In recent years the assembly of nanometer sized building blocks into two- and three-dimentional structures and functional materials has been an extremely active area of scientific research. A new class of materials, the DNA/nanoparticle hybrid materials and assemblies, which might have useful electrical, optical and structural properties, have been developed at Northwestern University. While characterizing particle morphology (size and shape) by subjecting it to the high vacuum environment in an electron microscope, the structure may have changed drastically from its natural state. The study of morphology of these DNA/Au nanoparticles in the liquid state was thus undertaken to further our understanding of the dynamics of the nanoparticles in a specific environment. This paper presents an in-situ observation of DNA/Au nanoparticle assembles in liquid media using environmental TEM.

Experiments were carried out with citrate-stabilized colloidal Au particles averaging 8 and 31 nm in diameter. Colloidal Au nanoparticles were obtained from a commercial source. 8 nm particles were modified with propylthiol-capped oligonucleotide, 3’HS(CH2)3-O(O)P(O)O-ATG-CTC-AAC-TCT, 1,whereas the 31 nm particles were modified with hexlylthiol-capped oligonucleotide, 3’TAG-GAC-TTA-CGC-O(O)P(O )O-(CH2)6SH, 2.
TECNAI: the Concept for Modern TEM/STEM Analytical Systems
Authors: Nadarzinski K
Published: July 2020

Decreasing dimensions and the necessity to understand the structure and composition of materials or devices on a nanometer scale has led to new developments in TEM. Previously EDX analysis had been established as the only analytical technique. In recent years the analytical capabilities of TEM have been augmented with a number of analytical techniques - such as electron energy-loss spectroscopy (EELS), electron holography, Lorentz microscopy, high-angle annular dark-field (HAADF). These have been developed or extended to yet unavailable levels of resolution. The Schottky field-emitters provide stable, reliable, coherent and high-current electron sources that are needed to get the best out of the mentioned analytical techniques.

The development of these analytical capabilities has been a parallel process in many different places and mainly led to dedicated microscopes optimized for one purpose only. This made it almost impossible to get different sets of analytical information from one specimen area simultaneously, and often the data even had to be collected from different specimens.
New Slow-Scan CCD Cameras (SSC) with Frame/Interline CCD Architecture Avoid TEM Shutter Control, Provide Excellent Image Quality and can be Easily Retrofitted
Authors: Hiller SA , Probst W , Seybold V , Zellmann E
Published: July 2020

Since it's introduction into TEM in 1986 [1] SSCs have become an effective and easy-to-use solution for acquiring high quality digital images electronically. Their main advantages are excellent linearity, very high dynamic, high sensitivity, and low noise. These advantages have made SSCs a nondispensable tool for quantitative image analysis. Moreover, since SSCs make high quality TEM images available in a computer within fraction of seconds, on-line image processing and software driven automated TEM tuning has become possible [2]. Many of the experiments which are performed nowadays in the area of high resolution, low dose, holographic reconstruction, and EFTEM [3] would not be possible without the digital input coming from SSCs.

Like recording images with a film sheet camera, digital recording of images with SSC requires control of the TEM beam blanker (shutter) by the SSC synchronised with the image acquisition process.

This blanker (shutter) control is a critical link in the chain to the digital image. Many older TEMs do not have direct access to beam blanking coils, or contrary to modern TEMs their coils are not designed to support hysteresis-free fast beam blanking, what is essential for acquisition of high quality digital images by a SSC.
Tomography on Point Projection X-Ray Microscope Using CCD Images
Authors: Newberry Sterling P
Published: July 2020

Recent advances with the cone-beam approach to tomography at the Advanced Microscopy and Imaging Laboratory (AMIL) have opened the possibility of employing tomography with the Shadow Projection X-Ray Microscope routinely when the specimen properties require it. The AMIL approach has been tested on small objects, without magnification, using conventional dental x-ray sources and a modestly diverging beam angle. The shadow projection Microscope, by contrast has a tenfold greater divergence and magnifies the specimen from unity to three or more orders of magnitude in resolution beyond the previous tests. The reader is reminded of the simplicity of the xray projection method and of the clarity of its images in fig. 1 and 2. The microscope can be operated in any laboratory and readily transported to alternate locations. Now that the AMIL data base and algorithms for tomography can be handled by a Pentium II processor the data gathering and reconstructions can also be managed at any laboratory installation.
Multiport-Readout Frame-Transfer 5 Megapixel CCD Digital System for IVEM Applications
Authors: Fan GY , Peltier S , Lamont S , Young SJ , Dunkelberger Dana G , Ellisman M H
Published: July 2020

A multiport-readout, frame-transfer charge coupled device (CCD) digital imaging system has been successfully constructed and tested for intermediate-high voltage electron microscopy (IVEM) applications up to 400 keV. The system employs a back-thinned CCD, made by MIT Lincoln laboratories, that comprises 2560 × 1960 pixels and a pixel size of 24 μm × 24 μm. With a frame transfer design, the imager fills nearly the entire usable area of a 100 mm-diameter silicon wafer (FIG. 1). In the current implementation, four of the eight on-chip readout ports are utilized in parallel each operating at a pixel rate of 1 or 2 MHz so that the entire CCD array can be read out in as short as ∼0.6 seconds. The frame-transfer readout functions as an electronic shutter which permits the rapid transfer of charges in the active pixels to four light-shielded buffers (FIG. 1) where the charges are readout and digitized while the active area of the CCD is integrating the next frame. At 2 MHz, charge transfer of 980 CCD rows will be completed in under 0.5 ms, which is much shorter than a typical exposure time of a few seconds. The camera head (FIG.2) and control electronics for CCD sensor were packaged by Photometries (Tuscon, Arizona). Two MaxVideo 200 image processing boards from Datacube (Peabody, MA) are used for high speed online imaging processing. The CCD sensor is electronically cooled to ∼ −40°C during operation.
Automated Acquisition of Cryo Electron Micrographs Using Leginon
Authors: Carragher B , Jojic N , Milligan R A , Kisseberth N , Pulokas J , Potter CS , Reilein A
Published: July 2020

Molecular microscopy is one of the most important structural approaches in cell biological investigations and can provide insight into complex biological questions that no other technique can provide. Currently, the technique typically requires the acquisition of very large numbers of transmission electron micrographs from frozen hydrated specimens using low dose techniques. The field is constrained by manual data acquisition methods that are slow, labor-intensive and result in a very low percentage of suitable images. We have developed a system, called Leginon, for automatically acquiring images from a transmission electron microscope. Our first prototype of this system demonstrated that we could acquire 1000 high magnification images per day from negatively stained catalase crystals. We have now extended this system to acquire low dose images of specimens embedded in vitreous ice.

Methods: Specimens were prepared on Quantifoil grids using techniques which have been described previously. The Leginon system uses a Philips CM200 TEM and a Gatan MSC CCD camera and is controlled by the emScope software library. The overall acquisition protocol requires (i) obtaining a low magnification image [660x] of a grid square from a Quantifoil grid (fig. 1a); (ii) automatically identifying holes containing ice of suitable thickness; (iii) acquiring an intermediate magnification image [6600x] of the identified hole (fig. 1b); (iv) identifying features of interest within the hole; (v) focusing at high magnification [38,000x] and finally (vi) acquiring a high magnification image (fig 1c,d).
Development of Cartilage and Bone During Formation of Phalanges by Tissue Engineering
Authors: Landis W , Isogai N , Vacanti J
Published: July 2020

Treatment of human congenital malformations and for loss of tissue or organ function is a serious clinical concern, frequently supported by harvesting autogenous tissue for reconstructive surgery. This paper summarizes an alternate approach through novel tissue engineering methods and describes cell-polymer composites that could be fundamental in developing advances for digit and joint replacement. The work utilizes cells from different sources transplanted on biodegradable polymer matrices to form structures with defined shape, morphological features and composition resembling those of human phalanges and intact joints.

Polyglycolic acids (PGA) fibers (Albany International, Mansfield, MA) 15 μm in diameter were used as a mesh support for cell attachment and matrix formation. For cartilage and tendon cells, PGA alone served as a flat surface without specific shape. For bone cells, PGA was copolymerized with poly-L-lactic acid (PLLA) (Polysciences, Warrington, PA) and shaped after a human phalanx molded from cadaveric distal and middle phalangeal bones. Polymers were sterilized with ethylene oxide before use.
Elastin-Mimetic Covalently Crosslinked Synthetic Protein Networks: Solvent and Temperature Dependent Morphological Features Imaged by SEM
Authors: McMillan R A , Apkarian R P , Conticello V P
Published: July 2020

Gel networks that mimic the properties of naturally occurring mammalian elastin have been synthesized for the development of novel biomaterials. Hydrogels with controllable and predictable mechanical properties are pursued for use in drug encapsulation and delivery systems, as scaffolds for tissue engineering and for the development of prosthetic implantable devices. The techniques of genetic engineering and microbial expression have been used to produce a 90KD recombinant protein based starting material that was polymerized into a solvent swollen gel network by the introduction of covalent bifunctional crosslinks at regularly spaced lysyl residues. SEM methods have been used to describe solvent and temperature dependent structural features.

The polypeptide precursor to the elastin-mimetic gels, poly[(VPGVG)4VPGKG], was obtained through bacterial expression (pET system) of an oligomerized gene coding for tandem repeats of the monomer. Gel networks were formed by crosslinking the protein with a bifunctional NHS-ester in both water and anhydrous DMSO. For conventional below-lens SEM studies, samples were dehydrated in an ethanol gradient, critical point dried from CO2(l), mounted on stubs with carbon tape and sputter coated with a 4-6 nm layer of Au/Pd.