Scanning Electron Microscopy
Scanning electron microscopy is an imaging technique used to obtain a sample’s surface topography. The scanning electron microscopy technique was first discovered shortly after the first commercial TEM was introduced. The first “stereoscan” microscope was brought to market in 1965 by the Cambridge Scientific Instrument Company. A scanning electron microscope provides a stereoscopic view of a samples surface. The electron beam is focused into a small spot on the sample and moved in a raster scan pattern across its surface. The beam interacts with, and is reflected off of, the surface of the sample. An image is formed from the back-scattered electrons that are reflected off of the sample and land on the Back-Scatter Electron (BSE) Detector. The BSE detector is broken down into quadrants which helps in offering multiple view angles of the object being scanned. SEMs produce interesting imaging results that are very different from those produced by a transmission microscope, making them important analytical tools that enable a completely different view of a specimen sample.
Conventional SEM Microscopes
SEM microscopes operate with voltages between 500V-30kV and come in all shapes and sizes. They can vary from benchtop formats all the way to large microscopes that fill entire rooms. They can be built with different types of electron sources and detectors. The price of an SEM varies with its size, reaching prices of over $1M. Large SEM’s depend upon staff with special training to be able to operate and perform regular maintenance on their electromagnetic coils, cold water circulation and electron sources. Benchtop SEM devices range widly in terms of price and performance.
How LVEM does SEM
The LVEM5 is a unique microscope in that it can instantly switch from transmission electron microscopy mode to scanning electron microscopy mode, effectively allowing the targeted area of a sample to be imaged in both modes without ever having to displace the sample or reconfigure the column. The ability to switch from TEM to SEM in mere seconds is a feature exclusive to the LVEM5 benchtop microscope. In SEM mode, backscattered electrons are dependent on the backscatter coefficient. Where the number of backscattered electrons are in direct correlation to an increasing atomic number of a specimen. The low-voltage source of the LVEM5 guarantees high-contrast imaging due to an elevated amount of BSE’s emitted from a specimen, and this in turn reduces the volume of charging artifacts that could otherwise disrupt the clarity of an image. The field emission gun takes the imaging quality a step further with its ultra-bright, high-resolution capabilities. Furthermore, the LVEM5 is simple and intuitive enough to operate without specially trained staff, and requires very little maintenance. It does not require any special facilities for installation, and takes up very little lab space. For more details, please visit the product details page for the LVEM5.
LVEM Sample Prep for SEM
The LVEM5 uses lower voltages, so it is well suited to image non-conductive samples. However, similar to conventional SEM, best results are obtained from conductive samples or samples that have been coated with a very thin conductive layer. Materials placed on a specimen holder do not have to be thin-sectioned like those done by TEM analysis, but samples do need to be completely dry. For more details, please visit our page on sample preparation.
Visit our photo gallery for a better look at what scanning electron microscopy within the LVEM5 microscope can do for you.
EXAMPLES OF SEM SAMPLES
- Metals and alloys
- Polymers and composites
- Ceramics and hard coatings
- Viruses and phages
- Biologic tissue
- Nano to micro sized Particles
- Nanofiber mesh
EXAMPLES OF SEM APPLICATIONS
- Engineering of artificial organs
- Study of food microorganisms
- Colloidal drug delivery systems
- Subcellular analysis
- Cell and tissue morphology
- Micro-electrical-mechanical systems (MEMS)
- Failure analysis of integrated circuits
- Surface topography of bulk materials
- Surface composition of bulk materials
Interested in learning more about our family of low voltage electron microscopes?