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Wet specimens are notoriously difficult to image in scanning electron microscopes (SEM) owing to evaporation from the required vacuum of the specimen chamber. Traditionally, this issue has been addressed by increasing the specimen chamber pressure. Unfortunately, observation under high specimen chamber pressure cannot prevent the initial evaporation effects. The wet cover method, where the original surface water is retained (and, therefore, considered wet), provides a way to introduce and subsequently image specimens that are sensitive to evaporation within a SEM, while preventing evaporation-related damage, and to observe interesting specimen–water interactions.

JEOL’s Particle Analysis Software 3 (PA3) enhances the capability of your analytical SEM by automating the detection, EDS analysis and classification of particles, grains or other features in your samples. Fully integrated with our SEM-EDS systems, PA3 increases throughput and productivity by providing fast, unattended measurements across large areas of a sample, or multiple samples.

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. A few of the disadvantages are that for efficient freezing, the sample size must be small and the price may not be in everyone’s budget for a state-of-the-art cryo system with freezing station, cold stage, vacuum transfer system etc.

When a sample is exposed to the electron beam in a scanning electron microscope a variety of signals are generated. X-rays being one of those signals that can provide valuable insight into a materials chemical makeup. The collected X-ray signal includes background X-ray radiation and more importantly, X-rays of specific energies, that are characteristic of the elements present in the sample. For this reason, an energy dispersive X-ray detector (EDS) is one of the most common detectors that is added to a scanning electron microscope (SEM). It is used to not only determine the elements present in a sample but in many instances can give insight to the quantity as well as the spatial distribution of these elements over very small volumes.

The first commercially available SEM was introduced over 50 years ago and to this day there is still no internationally accepted standard for determining SEM resolution. To add to the confusion, each SEM manufacturer relies on their own sample and methods for determining resolution.

The first commercially available SEM was introduced over 50 years ago and to this day there is still no internationally accepted standard procedure for determining the resolution in an SEM image. To add to the confusion, each SEM manufacturer relies on their own sample and methods for determining resolution. Defining the edge of a particle manually is also always subjective in nature; values will differ from one person to the next based on how that person interprets or ‘sees’ the edge of a particle.

Since the Scanning Electron Microscope (SEM) was first commercialized about 40 years ago, the SEM has shown a remarkable progress. Now, many types of SEMs are being used, and their performance and functions are greatly different from each other. To utilize these different SEMs, it is essential to recognize their features, as well as to understand the reasons for the contrast of SEM images. Thus, this document material is aimed at helping SEM users and future SEM users to understand the basics of the SEM, including the instrument principles, specimen preparation and elemental analysis.

SEM is an indispensable tool for studying the microstructure of a wide variety of materials. The images generated are inherently a 2 dimensional representation of the sample surface. Unlocking the 3rd dimension by reconstructing a 3D model from multiple SEM images can enhance our understanding of complex microstructure. This 3D view is often more intuitive and surface metrology characteristics can be calculated.

In this interview, AZoM speaks to Vern Robertson, EPMA Product Manager at JEOL USA, about the benefits of using a low kV in SEM imaging.

JEOL is always making efforts to meet the needs of our customers in all areas including hardware and software of our instruments. Our efforts to grasp customer requirements include question and answer opportunities during technical seminars and meetings. Based on these questions, we have published this Q&A book.

Other Resources

  • Image Gallery
    View a selection of electron images
  • FAQs
    See answers from questions often asked about our SEM and Surface Analysis instruments
  • Links & Resources
    View our page of useful and interesting links to various electron microscopy resources
  • Videos
    View some product presentations of our instruments
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