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Electron Optics Service

Scanning Electron microscope
Electron Optics Instruments
Benchtop SEM

SEM Basics / Tabletop SEM

HOW SEM's WORK

A  Scanning Electron Microscope (SEM) uses focused beams of electrons  to  render high resolution, three-dimensional images. These images  provide  information on:

  • topography
  • morphology
  • composition

A schematic representation of an SEM is shown in Figure 1. Electrons are generated at the top of the column by the electron source.   They are then accelerated down the column that is under vacuum, which   helps to prevent any atoms and molecules present in the column from   interacting with the electron beam and ensures good quality imaging.

Electromagnetic lenses   are used to control the path of the electrons. The condenser defines   the size of the electron beam (which defines the resolution), while the   objective lens’ main role is the focusing of the beam onto the sample.  Scanning coils are used to raster the beam onto the sample. In many cases, apertures are combined with the lenses in order to control the size of the beam.

Different types of electrons are emitted from samples upon interacting with the electron beam. A BackScattered Electron (BSE) detector   is placed above the sample to help detect backscattered electrons.   Images show contrast information between areas with different chemical   compositions as heavier elements (high atomic number) will appear   brighter. A Secondary Electron (SE) detector  is placed  at the side of the electron chamber, at an angle, in order  to increase  the efficiency of detecting secondary electrons which can  provide more  detailed surface information.

APPLICATIONS

Materials Science

SEMs, Benchtop SEM's and Tabletop SEM's are used in materials science for research, quality control and failure analysis.

In   modern materials science, investigations into nanotubes and  nanofibres,  high temperature superconductors, mesoporous architectures  and alloy  strength, all rely heavily on the use of SEMs for research  and  investigation.

In fact, just about any  material science industry,  from aerospace and chemistry to electronics  and energy usage, have only  been made possible with the help of SEMs.

Nanowires for Gas Sensing

Researchers   are exploring new ways nanowires can be used as gas sensors by   improving existing fabrication methods and developing new ones.  Electron  microscopy is vitally important in “helping characterise  nanowires and understanding their gas sensing behaviour.”

Semiconductor Inspection

Reliable   performance of semiconductors requires accurate topographical   information. The high resolution three dimensional images produced by   SEMs offers a speedy, accurate measurement of the composition of the   semiconductor.

In fact, in just about all wafer  manufacturing processes, SEMs are one of three essential quality control  tools  used. In the case of repetitive daily quality control tests,  larger  monitors (19 inches) have been shown to reduce visual fatigue  for  inspectors.

Microchip Assembly

Microchip   production is increasingly relying on SEMs to help gain insight into  the  effectiveness of new production and fabrication methods. With  smaller  and smaller scales and materials, as well as the potential of  complex self assembling polymers, the high resolution, three-dimensional  capacity of SEMs is invaluable to microchip design and production.

As   the Internet of Things (IoT) becomes more prevalent in the day to day   lives of consumers and manufacturers, SEMs will continue to play an   important role in the design of low cost, low power chipsets for   non-traditional computers and networked devices.

Forensic Investigations

Criminal and other forensic investigations utilise SEMs to uncover evidence and gain further forensic insight. Uses include:

analysis of gunshot residue

jewellery examination

bullet marking comparison

handwriting and print analysis

examination of banknote authenticity.

paint particle and fibre analysis

filament bulb analysis in traffic incidents

Since   SEMs offer the ability to examine a wide range of materials at high  and  low magnification without sacrificing depth of focus, their use in   forensic sciences makes it possible to draw conclusions, identify   material origins and contribute to a body of evidence in criminal and   legal matters. The desktop Phenom GSR instrument is specifically  designed for automated gun shot residue analysis.

Biological Sciences

In biological sciences, SEMs can be used on anything from insects and animal tissue to bacteria and viruses. Uses include:

measuring the effect of climate change of species.

identifying new bacteria and virulent strains

vaccination testing

uncovering new species

work within the field of genetics

Soil and Rock Sampling

Geological   sampling using a scanning electron microscope can determine weathering   processes and morphology of the samples. Backscattered electron  imaging  can be used to identify compositional differences, while  composition of  elements can be provided by microanalysis. Valid uses  include:

identification of tools and early human artefacts

soil quality measurement for farming and agriculture

dating historic ruins

forensic evidence is soil quality, toxins etc.

Medical Science 

Broadly   speaking, SEMs are used in medical science to compare blood and tissue   samples in determining the cause of illness and measuring the effects  of  treatments on patients (while contributing to the design of new   treatments). Common uses include:

identifying diseases and viruses

testing new vaccinations and medicines

comparing tissue samples between patients in a control and test group

testing samples over the lifespan of a patient

Art

Not   all SEM applications are strictly practical. Micrographs produced by   SEMs have been used to create digital artworks. High resolution three   dimensional images of various materials create a range of diverse   landscapes, image subjects are both alien and familiar.

A PRACTICAL AND USEFUL TOOL

Within  the fields of industrial application and research, there is an   increasing focus on quality control at microscopic scales. Achieving   high resolution imagery with a scanning electron microscope can provide   insight into many fields, making SEMs indispensable tools across many   fields.

Need help finding the right electron microscope equipment for your application?  

Tabletop SEM, Benchtop SEM and Desktop SEM