How SEM ( Scanning electron microscopy) is different from TEM (Transmission Electron Microscopy) ?

 SEM ( Scanning Electron Microscope) and TEM (Transmission Electron Microscope)

A useful technique for obtaining high-resolution images in a range of fields, such as technology, forensics, and biomedical research, is electron microscopy. Compared to optical microscopes, electron microscopes are able to obtain images with significantly higher resolution, which provides information that would not be possible otherwise.

Every electron microscope operates by directing a concentrated stream of electrons toward a sample while they are in a vacuum. Similar to how light is used in optical microscopes to form images, interactions between the electron beam and the material produce images. The resulting image provides information on the internal or external makeup of a sample, depending on the kind of electron microscope that is being used.

The two most popular forms of electron microscopy are Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The sorts of pictures that can be captured and the ways in which TEM and SEM operate are different. The definition, operation, and comparative analysis of SEM and TEM are covered in this article.

TEM can stand for Transmission Electron Microscopy or Transmission Electron Microscope (TEM) :

          An image of a sample's interior structure can be produced using a wide electron beam in a type of electron microscope known as a TEM. Sample morphology, composition, and crystal structure are all shown in detail in a picture produced by passing an electron beam through the sample.

How SEM different from the TEM ? 

 The Science Behind TEM: Mechanism and Function Explored

The electron beam is directed toward the specimen by the condenser after being produced by a heated tungusten in the electron gun. Magnetic lenses, which are doughnut-shaped electromagnets, are employed to focus the beam because electrons cannot flow through a glass lens. Due to the possibility of electron deflection from collisions with air molecules, the column holding the lenses and specimen needs to be under high vacuum in order to produce a clear image. A larger image of the specimen appears on the fluorescent screen when electrons that pass through are utilized to create an expanded image of the specimen. Denser spots in the specimen are termed to be electron dense because they scatter more electrons and appear darker in the image because fewer electrons hit that portion of the screen. 

In order for electrons to flow through samples, they frequently need to be extremely thin—less than 150 nm thick. A two-dimensional image is produced once the electrons have passed through the material and reached a detector below.

TEMs offer a remarkable 10–50 million times magnification capacity. The maximum resolution possible with an electron microscope, the details are shown down to the atomic level. TEMs are frequently employed in the study of cellular and molecular structures.

 The Science Behind SEM: Mechanism and Function Explored

The SEM scans the specimen back and forth over it with a narrow, tapered electron beam in order to produce an image. Surface atoms are struck by beams that release a tiny shower of electrons known as secondary electrons, which are then captured by a specialized detector. A secondary electron strikes the scintillator, producing a flash of light that is amplified and converted into an electric current by a photomultiplier. A cathode ray tube receives the signal and produces an image similar to a television picture that can be seen or captured on camera. 

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