$tem diffraction pattern analysis$

$tem diffraction pattern analysis$

The image strikes the phosphor screen and light is generated, allowing the user to see the image. The image then passed down the column through the intermediate and projector lenses, is enlarged all the way. Optional objective apertures can be used to enhance the contrast by blocking out high-angle diffracted electrons. This transmitted portion is focused by the objective lens into an image on phosphor screen or charge coupled device (CCD) camera. The beam then strikes the specimen and parts of it are transmitted depending upon the thickness and electron transparency of the specimen. This beam is restricted by the condenser aperture, which excludes high angle electrons. The beam of electrons from the electron gun is focused into a small, thin, coherent beam by the use of the condenser lens. Thus, TEMs can reveal the finest details of internal structure - in some cases as small as individual atoms.įigure 1 - General layout of a TEM describing the path of electron beam in a TEM (Taken from JEOL 2000FX Handbook)įigure 2 - A ray diagram for the diffraction mechanism in TEM Imaging Because the wavelength of electrons is much smaller than that of light, the optimal resolution attainable for TEM images is many orders of magnitude better than that from a light microscope. The TEM operates on the same basic principles as the light microscope but uses electrons instead of light. High resolution can be used to analyze the quality, shape, size and density of quantum wells, wires and dots. TEM can be used to study the growth of layers, their composition and defects in semiconductors. A high energy beam of electrons is shone through a very thin sample, and the interactions between the electrons and the atoms can be used to observe features such as the crystal structure and features in the structure like dislocations and grain boundaries. The transmission electron microscope is a very powerful tool for material science.

$tem diffraction pattern analysis$

Tem diffraction pattern analysis