Energy-Filtered Transmission Electron Microscope (EFTEM)

Energy-filtering transmission electron microscope (EFTEM), developed about ten years ago, is now a routine analysis tool in the characterization of materials.

History

It is a technique used in Transmission electron microscopy, in which only electrons of particular kinetic energies are used to form the image .

The ability of an energy-filter to show a two-dimensional distribution of a specific element.

The images at an energy-loss between 100 and 200 eV.

EFTEM

JAWAD AZAM (MME-10E-10)

If a very thin sample is illuminated with a beam of high-energy electrons, then a majority of the electrons will pass through the sample but some will interact with the sample , Scattered elastically or in elastically , Inelastic scattering results in both a loss of energy and a change in momentum

PRINCIPLE

If the electron beam emerging from the sample is passed through a magnetic prism, then the flight path of the electrons will vary depending on their energy.

It is possible to place an adjustable slit to allow only electrons with a certain range of energies through, and reform an image using these electrons on a detector.

The energy slit can be adjusted so as to only allow electrons which have not lost energy to pass through to form the image.

MUHAMMAD YOUNIS (MME-09E-30)

It consists of two main parts: Magnetic prism Optical column

PARTS

ZIA UR REHMAN (MME-09E-09)

In the curved magnetic field, electrons with different energies are dispersed, obtained at the end of this part.

The magnetic prism is the same as in a parallel electron energy loss spectrometer

Magnetic prism

An energy range is selected by a slit located at the dispersion plane.

In imaging mode, and an energy-filtered image occurs at the end of the GIF, where a slow-scan CCD camera is installed for image recording.

Optical column

FAHAD KASHIF (MME-10E-19)

Spatial resolution refers to the size of the smallest object that can be resolved on the ground.

In a digital image, the resolution is limited by the pixel size, i.e. the smallest resolvable object cannot be smaller than the pixel size.

The spatial resolution obtained in an EFTEM image is influenced by the specific details of the experiment itself:

Spatial Resolution in EFTEM Images

When doing EFTEM at high magnifications elastic contrast that is always present in EFTEM images may become visible. as th collection angle.

Spatial Resolution in EFTEM Images

Energy filtering can be applied for various problems:

Zero-loss filtering : Electron spectroscopic imaging :

Problems

KHIZER REHMAN (MME-10E-18)

Zero-loss filtering removes the contribution of all in-elastically scattered electrons to

both images and diffraction patterns.

By using only the zero-loss beam, all in elastically scattered electron are omitted (reduction of noise).

That leads to increased contrast and the resolution in TEM images.

Zero-loss filtering

By using electrons with a well-defined energy loss (ionization edge), elemental distribution maps can be generated.

Electron spectroscopic imaging