If you are sent to an analytical lab and told to characterize your solid sample using Scanning Electron Microscope, but you are clueless, use these points to master the powerful machine:
1. Principle of Scanning Electron Microscope (SEM):
The SEM is based on the principle of applying a high voltage electron probe on a solid sample so that the beam can interact with the loosely bound outer electrons of the sample atoms. The process is for producing Secondary Electrons that are analyzed to get the structural information of the sample.
2. Instrumentation of a Scanning and Transmission Electron Microscopy:
Scanning and Transmission Electron Microscopes have the standard instrumentation, which is outlined below:
- A Field-emission electron gun that focuses the electron beam on the sample under analysis.
- Magnetic Lenses: Used to adjust the breadth of the electron beam. Generally, the more powerful the electron beam, the higher the resolution image you get.
- A scanning coil.
- A secondary electron detector for SEM. This detector is used to detect the secondary electrons from the SEM.
- A monitor for displaying the high-resolution image. The secondary electron signals are amplified using amplifiers and transferred to the liquid-crystal display monitors for a 2D image display. The resolution depends on the number of secondary electrons that are being detected. You can amplify and lower the image resolution as you require.
- A complete vacuum system. The efficiency of the vacuum system will determine the image quality and resolution. A faulty vacuum system often destroys the filament.
3. Scanning Electron Microscope Resolution:
The better the resolving power a microscope has, the better it can identify two closely spaced objects as identical entities. An average Scanning Electron microscope principle has a resolution power of 10 nm (i.e., 10-8 m).
4. Sample preparation in Scanning Electron microscope:
In SEM, the sample preparation does not require any particular guidelines if the sample conducts electricity. However, if the sample is a non-conducting material, the sample must be coated using a conducting material such as metals.
However, in TEM, the sample preparation has many guidelines to follow. These guidelines are different for different instruments and should be consulted while experimenting.
5. Which scattered radiation do you need to collect in a Scanning Electron Microscope?
When the electron beams interact with the outer electrons of the sample, the following signals are radiated from the sample.
- Secondary electrons, used in the scanning electron microscope resolution.
- Backscattered Electrons,
- Auger electrons,
- Continuum spectra X-rays,
- Characteristic X-rays,
- Cathodoluminescence (CD),
- Fluorescent X-rays,
- Transmitted electrons, used in the Transmission electron microscope,
- Diffracted electrons, and
- Scattered electrons.
We record and amplify the signal we get from the Secondary electrons from the detector and use that to form an image in the Scanning Electron Microscope.
6. Can we analyze wet and Organic samples in SEM? Yes, in Environmental Scanning Electron Microscope (ESEM):
There is a special type of Electron Microscope called Environmental Scanning Electron Microscope (ESEM) that uses a gaseous chamber, and we can analyze hydrated (i.e., wet) and even biological samples (like spider webs), and we do not even need to coat them with metals as you did in the above point.
7. Time required for carrying out an SEM experiment
It takes as low as Five minutes to run a sample, extract the data, and get the SEM image of the sample.
8. Can you reuse the sample used once in SEM?
The SEM used a non-destructive electron beam, so we can use the sample for further analysis.
9. How much does a Scanning Electron Microscope cost?
Owning a Scanning Electron Microscope principle for a single individual is a tough job, as the cost of a Scanning Electron Microscope can range from $80,000 to $2,000,000. Now, owning an SEM is not the only thing, as you also need an operator (in case you cannot operate and analyze the machine on your own) and maintenance costs. Maintaining an SEM is also a tedious job as you can hardly find any person who can fix your machine. Only the service providers can restore the machine in case of any disturbance, which also doesn’t come at a cheap rate.
So, you see, as the Scanning Electron Microscope can provide a 3D topography of your sample, it also has a pretty high demand as you require a good room to set up an SEM instrument. Your room must be:
- Using a reliable current source.
- Vibration-free environment.
- There should be no interaction of any electronic or magnetic waves.
The uses and capabilities of a Scanning Electron Microscope have a wide range of applications in many industries, and they always own a fully equipped SEM machine to meet their purpose. You can use the above guide to get your job done using Scanning Electron Microscope. We hope the article clears out the query – How much does a Scanning Electron Microscope cost?