SEM Specimen Research Articles

Use of gold/palladium surface replicas for high kV (30),sem examination of low Z materials

A procedure for making high fidelity gold/palladium surface replicas of various low atomic number (Z) materials for SEM examination has been developed. The procedure facilitates simultaneous replication of a number of SEM specimens. These replicas provide improved image quality, elimination of charging and beam penetration artifacts and microtopographical information, often not available by direct SEM examination of low Z materials at 30 kV.

Semiquantitative analysis of rabbit knee articular surfaces based on stereomicroscopic examination of the cartilage.

A semiquantitative stereomicroscopic method was devised in order to examine rabbit knee articular surfaces. With the aid of a drawing tube mounted on a stereomicroscope, enlarged pictures (magnification of X 14-19) of ink-stained or SEM specimens of joint surfaces were drawn and the structural details classified. The point-counting method or a computer-coupled analyzer was used to analyze the pictures. The data thus obtained underwent statistical evaluation. The method proved to be very useful for the quantitation of experimentally induced changes on cartilage surfaces.

Uses of carbon in mounting frozen hydrated tissue specimens for SEM

Uses of carbon in mounting frozen hydrated tissue specimens for SEM

A Modified, Short Protocol for Preparation of Bryophytes for Scanning Electron Microscopy

Live bryological specimens can be prepared for scanning electron microscopy in under one hour without prior fixation by dehydrating with 2,2-di- methoxypropane followed by critical point drying. Unfixed specimens exhibited little distortion, thus eliminating the requirement for prolonged and/or expensive fixation that may cause collapse of cell walls or other artifacts. Critical point drying of specimens prior to examination by scanning electron micros- copy (SEM) is now a generally accepted procedure and its utility in bryology was dem- onstrated by Magill, Seabury and Mueller in 1974. Muller and Jacks (1975) proposed the use of 2,2-dimethoxypropane (DMP) for the rapid preparation of biological specimens for transmission electron microscopy. This procedure was adapted by Johnson et al. (1976) to specimen preparation for SEM. This adaptation required fixation in glutaraldehyde and osmium, prior to dehydration in 2,2-dimethoxypropane and critical point drying (CPD). The essential element of the procedure is dehydration by DMP, which upon exposure to water instantaneously hydrolyzes to form acetone and methanol. Johnson et al. (1976) suggested that fixation of specimens may be unnecessary. In an effort to simplify and shorten fixation and dehydration schedules, the effects of DMP dehydration on fixed and unfixed material were tested using leafy and thalloid liv- erworts and mosses. The protocol reported here yielded acceptable specimens for SEM

A simple SEM specimen holder for use in sputtering yield measurements

A simple SEM specimen holder for use in sputtering yield measurements

Utilization of aminoplastics as an alternative biological SEM specimen preparation technique

Utilization of aminoplastics as an alternative biological SEM specimen preparation technique

Characterization of protein gels by scanning and transmission electron microscopy A methodology study of soy protein gels

Different preparation techniques for scanning (SEM) and for transmission electron microscopy (TEM) were compared in order to characterize the structure of protein gels. SEM specimens were prepared by chemical fixation, dehydration, and critical-point drying. TEM specimens were prepared by using techniques of thin-sectioning and freeze-fracturing/etching. Thin sections were made after varying fixation and staining conditions. For freeze-fracturing/etching, the standard freezing procedure both using and omitting cryoprotectants (glycerol), as well as a particular modification of the “soil-emulsion” freezing technique without cryoprotective pretreatment were used. Finally, critical-point dried specimens (produced for SEM) were freeze-etched after infiltration with dioxane. The various techniques of preparation were applied to soy protein gels made in distilled water and in 0.2 M NaCl under well defined conditions. The gel structures differed with regard to the state of aggregation which depended on the presence or absence of NaCl. The network structure was found to be of two levels. First, there was an orientation on the molecular level in the form of strands and fine ring structures. Second, there was a coarser network with voids of the magnitude of ≈0.2 μm. The pore size distribution of the latter network was found to be very sensitive to environmental factors such as low ionic strength and presence of cryoprotectants mainly due to swelling. The information obtained by the various techniques generally showed good agreement and were complementary. Distinct preparation artifacts caused by improper freezing or critical-point drying were also revealed.

Shrinkage in preparatory steps for SEM. A study on rabbit corneal endothelium.

Since specular microscopy of the cornea offers the opportunity to observe and measure cells in vivo without any outside interference this method forms an unrivalled basis for estimation of tissue shrinkage during various preparatory methods. Therefore a study was performed with the purpose of evaluating the degree of artifacts in each preparatory step from the living tissue "in vivo" to the final SEM specimen. The study was performed on rabbit corneas, the endothelium serving as measuring target. The in vivo state was recorded by specular microscopy. Unfixed corneas were studied by light microscopy unstained and stained by alizarin red S or silver nitrate. Fixation was performed intracamerally with 1.5% glutaraldehyde (Gla) by a pH, osmolarity, viscosity and intraocular pressure identical with the physiological values of rabbit eyes. Fixation was completed by immersion in 2.5% Gla for 1/2 h. Gla-fixed corneas were evaluated as above before osmification. Dehydration was performed either by graded acetone, by acetone in a gradient-free system, both followed by critical point drying (CPD). At all steps cells were counted using the same reference frame. The number of cells/mm2 was estimated and statistical analysis showed a shrinkage of 22 per cent (area) in unfixed tissue, 26 per cent (area) in normally dehydrated tissue and 37 per cent (area) in gradient free dehydrated tissue processed for SEM.

Scanning and Transmission Microscopy of Microbial Flora Adherent to Colonic Polyps

Fiberoptic colonoscopy was used to obtain mucosal biopsies of colonic polyps and normal mucosa for the purpose of studying microbial ecology and mucosal adherence in vivo. These studies involved the taking of multiple mucosal biopsies throughout the length of the large bowel, specifically biopsies of colonic polyps (adenomatous and hyperplastic) and the areas immediately adjacent to them. Earlier observations have documented the feasibility of this technique for studying microbial populations in situ1. The mucosal samples were evaluated by quantitative bacteriology, transmission microscopy and scanning electron microscopy. The colonic mucosal biopsies obtained during routine colonoscopy were immediately prefixed in 3% glutaraldehyde buffered in 0.1M sodium cacodylate. Those specimens for TEM were postfixed in 1% osmium, dehydrated and embedded in Epon. Biopsies for SEM were prepared according to the OTO method described by Kelley2. Specimens for TEM were observed in a Phillips 300 at 80KV, while specimens for SEM were processed in a Phillips 500 at 25KV with a spot size of 80Å.

Improved handling of structural fragile cell-biological specimens during electron microscopic preparation by the exchange method.

An exact method of preparation of soft biological specimens for electron microscopic analysis of surface fine structures is described. It allows routine preparations of fragile specimens for SEM and TEM imaging modes. With this procedure physical preparation parameters such as mechanical loads on the specimen surface or changes of temperature are controlled. The wet specimens are premounted in cheap disposable BEEM-containers or glass boats and are constantly kept under liquid in a closed system. The exchange of preparation media is performed continuously and, if necessary, over gradients. For comparative investigations with different EM-modes, at each step of the procedure parts of the specimens may be removed for individual processing. Conventionally prepared critical-point dried specimens are compared to those processed by the exchange technique and preservation of surface fine structures is demonstrated. Shadow-casted clathrin cages and stereo-replicas of virus infected cell cultures are shown in TEM preparations. For SEM, coverslip cell cultures and isolated glomerulus basement membranes are prepared and an additional flat embedding for TEM ultrathin sections is demonstrated.

Practical hints and tips

ScanningVolume 3, Issue 4 p. 302-302 Practical Hint and TipFree Access Practical hints and tips First published: 1980 https://doi.org/10.1002/sca.4950030410Citations: 11AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Reference Göcke R: A thermoplastic glue for SEM specimen mounting. Scanning 1, 63– 64 (1978) Citing Literature Volume3, Issue41980Pages 302-302 ReferencesRelatedInformation

Thin films for SEM specimen coatings: The backscattered electron contribution

ScanningVolume 3, Issue 3 p. 210-214 Original PaperFree to Read Thin films for SEM specimen coatings: The backscattered electron contribution M. R. Sogard, M. R. Sogard Enrico Fermi Institute and Physics Department, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, USASearch for more papers by this author M. R. Sogard, M. R. Sogard Enrico Fermi Institute and Physics Department, The University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, USASearch for more papers by this author First published: 1980 https://doi.org/10.1002/sca.4950030313Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume3, Issue31980Pages 210-214 RelatedInformation

Direct grounding tool for examination of uncoated specimens in the scanning electron microscope.

By combining a micromanipulator, a medical cystoscope, and a forked specimen probe, a direct grounding tool for examination of uncoated specimens in the SEM has been developed, tested, and successfully demonstrated. It provides a valuable alternative technique when it is undesirable to coat SEM specimens. The apparatus is nondestructive, simple, and does not require major modification of the instrument. It provides the additional benefits of direct optical specimen orientation and viewing, allows better electron and x-ray resolution than conventional coating techniques, and is practical with a wide range of SEM objects.

Properties and applications of saddle-field ion sources

The operation of these dc-energized cold cathode sources is based on the effect that electrons describe long oscillatory paths in the presence of an electrostatic saddle potential field. A high probability thus exists of ionizing any gas present in the source, to maintain a discharge at considerably lower pressures (10−4–10−3 Torr) than in conventional cold cathode tubes without a magnetic field. Depending on the symmetry of the saddle-field, beams of various cross-sections are obtained: an axial field produces a high-intensity pencil beam (2 mm diameter), planar fields give rise to divergent beams (e.g.,extending to 25 cm diameter at 10 cm from the source operating at 20 mA, 2 keV). The beam contains a high proportion of energetic neutrals, or may be fully neutralized on emerging from the cathode aperture, depending on source geometry and applied field. Neutralization may be due to the recombination of ions with slow secondary electrons from the edges of the aperture. The operating pressure is compatible with filament and electron beam gun evaporation. Evaporation on a surface exposed to a saddle-field beam combines rapid deposition with strong adhesion characteristic of sputtered films. Other applications include preparation of specimens for TEM and SEM, cleaning and profiling for surface analysis, ion beam machining and sputtering. At present there appears no obstacle to further increasing the size and output of saddle-field ion sources.

Standardization of Specimens for SEM: The Specimen Disc-Permanent Stub System

Standardization of Specimens for SEM: The Specimen Disc-Permanent Stub System

A comparison of gold and platinum sputtered coatings for scanning electron microscopy

It is widely accepted that thin conducting films of noble metals have the desirable properties of high electron emission and high resistance to corrosion which fit them for use as specimen coatings for scanning electron microscopy. However, although Au and its alloys with Pd are regularly used for this purpose, deposited by either evaporation or sputtering, the use of Pt has apparently been ignored. The high evaporation temperature of this metal (2090°C against 1350°C for Au) makes its controlled evaporation inconvenient, but the recent commercial introduction of simple sputter coaters, coupled with developments in Pt plating technology, have made the sputtering of Pt on to SEM specimens a practical proposition. A comparison of the properties of sputtered coatings of Au and Pt has therefore been made; results given below show that satisfactory coatings may be made with Pt as conveniently as with Au, and that in some respects the Pt coatings are superior.

Prediction of X-ray spatial resolution for SEM and STEM specimens using Monte Carlo methods

Determinations of spatial X-ray resolution in conventional microanalysis in electron probe microanalysers where the beam is perpendicular to a smooth surface are now quite straightforward. However, SEM's and STEM'S are becoming increasingly used methods for performing microanalysis. The specimen arrangement for this sort of work often involves both inclined beam and detector geometries. Under these conditions X-ray correction constants have to be altered due to the changed average path length for the emerging X-rays. The spatial resolution and correction constants peculiar to the new geometry can be physically studied using a Monte Carlo computer method which simulates the trajectories of many electrons as they interact with the specimen.Another attempt to predict resolution and effective take-off angle using single electron scattering theory has been made for thin films. This over estimates the X-ray source size at large foil thicknesses and under estimates at small foil thicknesses. Experimental methods have been devised utilising edges and small, spherical particles.

Cutting teeth in the SEM

AbstractAn SEM was used to observe and record dental tissues as they were being cut. Sound human deciduous and permanent teeth were stored in 70% ethanol until required, then soaked in water, superficially dried and screwed to the SEM specimen stage through small drill holes made when they were wet. Many specimens were frozen and studied at cryogenic temperatures so that they would not become dehydrated. Edges used to cut the teeth included steel and tungsten carbide fashioned to resemble clinical cutting instruments, and diamond ultramicrotome knives and burs. The cutting tools were held either in a micromanipulator or a rigid tool post clamped to the specimen stage. The finest control was obtained by moving the specimen with the usual stage controls. SEM was conducted at 3 or 5 kV using TV speed scanning on the uncoated samples. All experiments were video‐taped. 3‐D control was difficult with a mono image and a real‐time stereo system was therefore developed.Continuous, flowing sections of enamel could be obtained using diamond knives to cut the prism‐free, surface zone tangentially. Thin sections of dentine, cement and bone curled up as they were cut, thus demonstrating permanent deformation. Subsurface enamel always fractured as it was cut, either locally as the tissue passed over the knife edge or tore out beneath the plane of the knife or by larger fragments cleaving off at larger distances ahead of the knife. Appearances were characteristic of prism orientation with respect to cutting direction. No anisotropy of cutting behaviour was found with dentine or bone: These tissues only fractured when thicker sections were taken.The SEM methods employed here can be usefully applied in the study of other materials.

Some simple techniques for coating heat-sensitive SEM specimens

Some simple techniques for coating heat-sensitive SEM specimens

Cyanide removal of gold from SEM specimens

The cyanide method is highly recommended for the purposes of the removal of gold coatings from SEM specimens prior to (a) further treatment before further SEM, and (b) staining and mounting for LM.