Vacuum System Inside of the e optical system and the spacmen chamber must be kept at high Vacuum of 10-3to 10-4 pa. Diffusion Pump does this. Mostly used : turbo mulecula pump. A Specimen pre-evacuation chamber (airlock chamber) While keeping a high vacuum in the Specimen chamber. Working SEM uses electrons instead of light to form an image A beam of 25 is produced at the top of the microscope by heating of a metallic filament The t beam follows a vertical path through the column of the microscope It makes its way through electromagnetic lense which focus and direct the beam down towcords the sample Once it hits the Sample other es, (backrattered 120) are ejected from the sample. Detectors collect the 2° or backsattered IS, and convert them to a signal that is sent to a vlewing Screen.
electrongun beam wondenser here magnification Scan Control generation scanner Display SE Detectos BSE Amplifier Sample Image formation e beam is focussed into a fine Probe , which is rethood scanned across the surface of the specimen u the help of scanning wils. Each Point on the specimen that is struck by the accelerated electron emits signal in the form of electronage radiation Selected Portions of this radiation usually secondary (SI and I a back rattered is (BSE), are: collected by a dets Resulting signal is amplified and displayed on a TV Street Computer monitor
Inudent e beam Xray 2 Backsoftered IS. Cathodolumiration Auger IS 2° electrone Absurbed is IIIII Transmitted is Emission of Various as and electromograte wave from Spainer 2° electron When the incident e beam enters the Specimen; 2° electron are produced from the emission of the valence es of the constituent atome in the specimen. Since the energy of 2° electron is very small, those generated at a deep region are quickly absorbed by the specimen only those generated at the top surface of the specimen are unitted outside of the specimen The means that 2° electrone are very sensitive. to the surface 2 electron is used to observe the topography of the specimen surface