Electron Optic Documents

SEM manufacturers can choose different output sizes for their images, making magnification a very deceptive number when comparing SEM micrographs from different SEM manufacturers. Because of this fact, the best way to compare images is to compare the length of the micron bar or field of view.

There are a number of applications where scientists and engineers are faced with air or moisture sensitive samples that require imaging and analysis using a scanning electron microscope (SEM). Applications include: components in rechargeable batteries, fuel cells, and catalysts among others. Any exposure to oxygen or moisture in the air can completely alter or destroy the structure of these highly reactive materials. JEOL has built a special air-lock system that can handle the transfer of air-sensitive specimens to be imaged in the SEM without atmospheric exposure.

The ability to increase the probe current for fast microanalysis, while still maintaining a small spot size and small volume of excitation for high resolution, has been the holy grail of microanalysis in SEM. One of the unique features of JEOL’s FE-SEMs is the patented Aperture Angle Control Lens (ACL). This lens automatically optimizes for both high resolution imaging at low probe currents and high spatial resolution X-ray analysis at high probe currents with a seamless transition between the two.

Scanning electron microscopes (SEM) coupled with an energy dispersive X-ray detector (EDS) are used extensively to provide insight into a sample’s chemical makeup. This SEM-EDS technique can provide information on the elements present, their relative concentrations and spatial distribution over very small volumes (micron and some instances nanometer scale).

The holy grail of nanoscale analysis with EDS is to quickly analyze any features which can be imaged in the SEM. However, for nanoscale features this is complicated by that fact that X-ray spatial resolution is typically larger than SEM imaging resolution. Figure 1 shows EDS maps from an integrated circuit cross section at 15kV and 6kV using a W SEM and an FE SEM, as well as the approximate X-ray signal depths at those voltages.

Cryo-SEM imaging is a powerful tool in studying the structures of electron beam and vacuum sensitive materials. These materials include: fragile biological structures such as fungi, plants, cells, etc. as well as soft or volatile samples and even liquids. Cryo-SEM offers some clear advantages by rapidly freezing a sample prior to imaging, thus maintaining the sample as close as possible to its natural state. Long dehydration and chemical fixation steps can be avoided. Inhibiting dehydration helps maintain delicate structures without shrinkage. Moreover, volatile or even liquid samples are stabilized under the electron beam. Cryo fracturing techniques allow for study of the internal microstructure of these types of vulnerable materials as well.

“Visualize the truth” is a hope of researchers who use various measuring equipment. Researchers who use electron microscopes as well have a desire to observe the real structure. But actually, in experiments using electron microscopes, many problems arise: They include damage regions of the specimen when it is cut for the size suited to observation, artifacts due to the staining that is applied to enhance image contrast, deformation caused by substitution of water to resin for withstanding vacuum exposure, and thermal damage to the specimen with electron-beam irradiation. As a result, the visualization of the real structure in the microscope image becomes increasingly difficult. One recommended solution is to cool the specimen, that is, “Cryo” techniques. This “Cryo Note” introduces some of the diversified cryo-techniques. We sincerely hope your challenge to observe the “real structure” will be solved by “Cryo” methods.

Scanning Electron Microscopes (SEM) support the development of new LIB technologies with morphological observation at the micrometer to nanometer scale, as well as the chemical analysis needed to create high-performance coatings and powders. Ultra-low voltage imaging combined with signal filtering in the SEM allows direct imaging and analysis of battery constituents (anode and cathode) with nanometer resolution. Additionally, one of the important aspects of the analysis is the ability to probe chemistry of the constituents at nm scale (Fig. 1). JEOL FESEM offers the ability to perform microanalysis with energy dispersive spectroscopy (EDS) at extremely low voltages to pinpoint localized makeup of the specimens and, in particular, low atomic number materials such as carbon and fluorine. Moreover, the unique JEOL Soft X-ray spectrometer (SXES) allows researchers to analyze Li.

In recent years with the advances in both EBSD and FE-SEM technology there have been renewed efforts at analyzing nanostructured materials at high temperatures using dedicated specimen holders and sub-stages. Although the techniques for EBSD analysis of bulk materials using heating stages have been well established [1], the requirements for nanostructured materials preparation and analysis obviously differs from bulk materials and can benefit from a miniaturized heater with smaller sample/higher temperature capacity capability [2].

Electron Backscatter Diffraction (EBSD) is a powerful technique capable of characterizing extremely fine grained microstructures in a Scanning Electron Microscope (SEM). Electron Backscatter Patterns (EBSPs) are generated near the sample surface, typically from a depth in the range 10 – 50nm. In order to achieve effective analysis it is imperative to combine high beam current with small probe size to achieve high spatial resolution in a time efficient manner.