Observe particles by using Scanning Electron Microscope (SEM), Energy Essay - 1

Observe particles by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray SEM and Transmission Electron Microscopy - Essay Example m. SEM-EDAX analysis shows that the powder particles are those of ytterbium oxide and TEM analysis shows morphology of fine TiO2 and Fe2O3. Results and analysis of these experiments are presented in this report. Introduction Electron microscopy has been a leap jump over optical microscopy in the field of micro imaging. While resolution in case of optical microscopy is limited by the wavelength of light, the same gets tremendously improved because accelerated electrons have much smaller wavelengths and hence much better resolution in case of electron microscopy. Besides, micro imaging there are other benefits associated with using electron beam as probe. This is because electron – matter interaction produces a wide variety of signals like secondary electrons, back scattered electrons, fluorescence and characteristic X-rays, transmission electrons, auger electrons etc. to name a few [1]. These signals do not contain information about only topography but also about chemistry of t he region of interaction and hence micro-analytical information can also be extracted. This is the reason why a large number of micro-imaging and microanalytical instruments have been developed using electron beam as probe and these are being widely used in the industry as well as in the advanced research. A brief introduction of some of these instruments like Scanning Electron Microscope (SEM), Scanning Electron Microscope with Energy Dispersive Analysis of X-rays (SEM-EDAX) and Transmission Electron Microscope (TEM) is presented in the following sections. Scanning Electron Microscope (SEM) [3]: This microscope scans the probe electron beam over a raster and response signals like secondary and backscattered electrons are collected and used for image formation [2]. It consists of a column always under vacuum consisting of different subcomponents. It consists of an electron gun or electron source. This is followed by condenser lenses to focus the beam. There are apertures in the path to allow only the useful (central) portion of the beam to the subsequent stages. The focused beam is double scanned and made to pass through an aperture to fall onto the specimen. The beam is scanned over the specimen in a raster and the generated signals – secondary or back scattered electrons are collected, amplified and again scanned in a raster onto a CRT screen in synchronized manner. Thus image is formed pixel by pixel. The magnification is ratio of the CRT screen size to the area of the raster onto the specimen. Because, the CRT size is fixed, therefore, magnification can be increased by scanning lower area onto the specimen and vice – versa. While secondary electron provides topographic contrast, the backscattered electrons provide atomic number or Z-contrast. SEM with Energy Dispersive Analysis of X-rays (SEM-EDAX): EDAX is essentially a detector or an attachment to an instrument. This is capable of detecting energy of the X-rays falling onto it. This uses a semiconductor – SiLi or GeLi and as X-rays fall onto this semiconductor electrons are produced in the proportion of the energy of the X-rays and this produces a current which is used to determine energy of the X-ray. This attachment can be attached to different instruments like SEM, EPMA or Electron Probe Microanalyser or even with a TEM or Transmission Electron Microscope. When probe electron beam falls onto a sample characteristic X-rays are produced, which are collected and analyzed