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Introduction To Scanning Electron Microscopy Introduction To Scanning Electron Microscopy At the completion of the prac, the practical experience of operating a
present. Gold nanoparticles have been used extensively as specific staining agents in biological electron microscopy. According to the Mie Scattering Theory, particle
and histologists in particular, where previously unimagined structures in cells were revealed. More recent developments in biological specimen preparation have come
resistance reached a plateau of 25-35 Ohm.cm2, which was similar to the small intestine. In transport studies 2/4/A1 cell line monolayers selectively restricted the
the homolog from Synechococcus sp. in which Dps was found to exist in hexameric form (47). Scanning electron microscopy of the family prototype, the E. coli-Dps protein,
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Introduction To Scanning Electron Microscopy
At the completion of the prac, the practical experience of operating a scanning electron microscope is sufficient to operate the particular machine in the future. During the experiment, two different gold plated samples are analysed under the SEM and compositional and topographic information is identified and analysed. Both the information is derived by changing the working distance, accelerating voltage, aperture size, probe current, resolution and magnification.
AIM
To analyse samples and obtain micrographs of the surface, using a scanning electron microscope. The experimental images are compared against the different material structures and defects between the various samples at different magnifications and resolutions.
INTRODUCTION
A schematic of a scanning electron microscope is shown below. The instrument can be separated into three major sections including electron-optical column', vacuum system and electronics and display system.
Figure 1: Layout off scanning Electron Microscope.
In the optical part of instrument, the first thing we notice is the need for a source of illumination. No visible photons of light are produced within the SEM but an invisible beam of electrons. The beam is produced from an electron gun' and a cross-section through a simplified electron gun is shown below.
Figure 2: Cross-section through an electron gun
A V-shaped tungsten filament (I) is heated electrically to about 2700Kand the high temperature causes many of the electrons in the tungsten to become sufficiently excited for them to escape. This process is called "thermionic emission".
Once freed the electrons would be quickly recaptured by the filament, because in losing them, it will have become positively charged. Applying a high negative voltage (typically 2-25 kV) between the filament and a nearby...
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