Using a Scanning Electron Microscope

this film will take you through the use of the scanning electron microscope or SEM to examine your samples the SEM is an expensive instrument and incorrect use will cause damage if you're in any doubt about a procedure you should ask for assistance before using the SEM you should have prepared your sample samples must be clean and dry before loading mount your sample on an aluminium stub using a sticky carbon tab it's important that the specimen is rigidly fixed to avoid vibrations the SEM should always be in microscope control before you begin if it isn't seek assistance to start the experiment press vent to let air into the vacuum chamber a dialog box will appear asking you to confirm that you wish to vent press ok venting will take several minutes and is complete when the word venting changes to idle once vented you can open the chamber door and fix your specimen onto the sample holder it's essential to set the sample height correctly to avoid damaging the detectors ensure that the highest part of the specimen is set to 10 millimeters with the elephant the sample height can be adjusted by turning the z control on the door of the SEM clockwise will raise the sample and anti-clockwise will lower it when the sample height is set remove the elephant 10 millimeters should roughly give you focus which can be refined later after carefully closing the chamber door ensure the SEM is in high vac it isn't obtain help from technical staff hold the door shut and click pump continue to hold the door until free back appears the SEM will take several minutes to reach full vacuum you cannot begin working until back ok appears once the SEM has reached high vacuum you must choose a detector SC is the most commonly used and will work on a majority of samples now choose an accelerating voltage for polymers start with either 5 or 10 kV for ceramics start with either 10 or 15 kV the metals start with either 15 or 20 kV we're looking at a metallic sample so we choose 20 kV now choose a spot size a low spot size will allow you to see finer detail but will be noisy a spot size of 5 is usually a good starting point at a magnification less than 10 thousand times now turn on the beam when operating in active boxes of gray and active ones are yellow once the beam is on a reminder will appear entitled microscope confirm focus do not press ok until you focus the image of your sample to refine the focus first press the video scope button a target region with alpha and lower boundaries marked by lines will appear on the screen set the contrast and brightness to 0 the screen should be black now increase the brightness till the oscillating line is on the lower boundary of the target region next increase the contrast until the oscillating line lies between the upper and lower boundaries the screen should now form a pale gray image not white click on the video scope button to close you can now focus the image using the mouse by holding down the right-hand button and moving the mouse left and right to focus the image once the image is sharp click OK on the microscope confirm focus box you have now calibrated the zero 'kiss you can now move around the sample looking for regions of interest using the arrow keys you can Center on a selected region by double clicking with the left hand mouse button the sample we're using for this film has been poorly coated to exaggerate what's seen on the monitor the features on your sample may not be so pronounced the magnification of your image can now be increased or decreased using the plus or minus buttons there's also a drop down menu that can be used to produce sharper images always focus at a magnification greater than you're going to use for imaging if your image is streaked your smear this is because the beam spot is not circular this can be corrected using the stigmata z' focus it's a magnification of 10000 times on a sharp feature now press and hold shift in the right mouse button this activates the stick martyr's move the mouse left and right to get the clearest image possible now move the mouse up and down to get the clearest image possible now refocus is normal repeat the procedure until you're satisfied with the quality of the image the final adjustments make is the scan rate the speed at which the beam moves across the sample surface is controllable in TB rate this motion is very fast and this mode is best used at low magnification to move rapidly across the sample looking for regions of interest the image may be noisy so switch to slow scan one or two to examine fine features in sharp detail when you're satisfied with your image you can acquire a photograph by pressing f2 this gives a single slow speed scan of the surface to save this frozen image select image from the in out drop-down menu then using up to eight characters name the image and press save to continue imaging unfreeze the screen by pressing the snowflake icon when you've finished imaging turn the beam off and bent the vacuum chamber when it's safe to do so remove your sample before leaving press pump to return the chamber to high back status and select the CCD option in the detector drop down menu do not leave until vac okay appears

Channel: University of Leicester

Views: 62,606

Keywords: SEM, Scanning Electron Microscope, University of Leicester, Chemistry, Engineering, How to use an SEM, Scanning, Electron, Microscope, Microscopy, Electron Microscope (Invention), Physics (Field Of Study), Computer, Electronics, Carl Vivian, Technology

Id: kNCCMK7l_rU

Length: 7min 16sec (436 seconds)

Published: Tue Mar 27 2012