University:
Swansea University
Course:
PM134 | Microbiology
Academic year:

2023
Views:

369

Pages:

3
Author:

Sanjeev KG

SEM I4 B a type of A Sample & microscope that by scanning it with a Produces ces images d focussed beam af - Powerful magnification tool that utilizes focused beay of Es to obtain informaction The interact with atoms in the sample, producing Various Signals that can be detected and that contain Signale the Information about the samples sufare topograpiy and composition. The beam is generally scanned in a roder Scan Porton and the beam's position is ombine with the detected, Signal to Produce, an Image SEM can achieve resolution better than Inm →The most emitted by Common mode. atomy excurtal of detection B by the t sby 2° election beam + The no. of 2° electron B a function of the angle b/w the Surfare and the beam. On a flad Suryaw, the Plume of 2° τ i's mostly contained by the sample, but on tilted surfare, the Plume is partially exposed and more es are emitted. By scanning the sample and detecting the d' is, an image displaying the tilt of the surfare. Ps created. Principle - A nommal SEM à microscope operates at high vacuum. - The base principle is that a beam of Is is generated by a suitable source, typically a tungsten filament / field emission gun. →The beam is accelerated I through a high Voltage (eg. 20 ку and pass through a system of apertiores and clectromagnetic lenses to produce a thin beam of electrons. →Then the boam Scans of the surface of the specimen by Means of scan oils. →Electrons are emitted from the specimen by the action of the Scanning beam and collected by Suitably-positioned detector. The microscope operator is watching the mage on a Soreen Imagine. a spot on the screen scanning + across the screen from left to right. At the end of the screen, it crops dow a line and scans across again, the process of being repeated down to the both of the screen. Components of SEM Electron Source Thermionk gun. field emission gun. Electro magnetic magnetic or electrostatik lenser. L Vacuum chamber. Sample chamber and stag. Detectors 2°nd I detector. Back scatter detector. Diffracted back scatter detector. X-ray Deteeter Instrumentation An electron Optical System. A Specimen Stage ③A 2 electron Detector Image. Display and Recording unit. Vacuun System.