Why do I have to check the beam current?
There are three types of currents measured in the FE-SEM column. The first is emission current (Ie), which is a measure of the electron current emitted from the tip and collected by the anode. Beam current, labeled Ib, is the measure of electron current that passes through the hole of the first anode. As the beam travels down the column, it is further reduced until it hits the specimen, at which point it is termed specimen or absorbed current. Ie current must be checked and set after the first 15 minutes of use, again after 30 minutes, and once more at 1 hour. This is because molecules in the gun chamber adhere to the FE-SEM tip when gas particles are released from the anode plate as the electrons bombard it. Those gas particles "stick" onto the tip, creating noise and drift of the beam, and lowering the Ie current. Resetting Ie at the specified intervals will reset the emission, which will stabilize the noise and drift, creating a noise-free image.
See Imaging under Operating Procedures in Hitachi S-4700 FE-SEM.
What is charging?
See Charging under Imaging Techniques in Hitachi S-4700 FE-SEM.
Why do I need to flash?
See Flashing under Operating Procedures in Hitachi S-4700 FE-SEM.
What should I do if the software stage position display is different from the stage position itself?
If the knobs are not positioned at X=12.5 mm and Y=12.5 mm, manually rotate the knobs on the stage until they come to that position. Then enter their values into the X and Y windows on the computer screen.
Why should I not touch the exchange rod?
When the sample rod is touched, grease is removed from the rod, which hinders smooth loading and unloading of the sample. Once it is on your fingers, it is likely to be transferred to your sample, which contaminates the inside of the microscope. This grease is also toxic.
What is the liquid nitrogen for?
We use LN2 for three purposes in the FE-SEM. The first purpose is to cool the EDS detector and reduce the thermally induced background, or "leakage" current, present in the signal. The second purpose involves the cold trap, which is a means of removing contaminants through a very low temperature surface that is exposed below the scope. The cold surface attracts vapor particles from the vacuum pumps, resulting in a cleaner specimen chamber environment, and lower specimen contamination. The third use of liquid nitrogen is through the cold finger. It is positioned directly above the specimen and attracts vapors released by the specimen-beam interaction.
How do I sign up for time on the FE-SEM?
Instrument calendars and instructions may be found under Access > Reservations in the main ACMAL website.
How much time should I plan on signing up for?
This depends on the amount of work you plan to accomplish, but 1 or 2 hours is reasonable. Read the Google Resource Calendar Instructions in Access > Reservations.
Do I have to take the class before using the FE-SEM?
YES! This is a very expensive piece of equipment and we do not want you to break it. Users must be certified, otherwise an external operator is required. To become certified, users must take and pass the SEM course offered by the MSE department. Upon passing the practical at the end of the course, a user must receive additional training for the FE-SEM.
See Policy > Standard Operating Procedures.
What is the correct order for shutting down?
There is a list of start-up, and shut-down procedures in the lab for users to follow, as well as in this module under "operating procedures". These instructions were written in a particular order so that the original default settings are resumed after each use. Use them!
See Shut Down under Operating Procedure in Hitachi S-4700 FE-SEM.
Can I switch between operating modes without changing other parameters?
Yes, one can switch between operating modes and accelerating voltage without changing any other parameters or shutting down the scope. Keep in mind, however, that the minimum working distance allowed changes with each mode. It is necessary to re-focus, align, and stigmate each time a mode is changed.
Can I change the Accelerating Voltage without shutting the scope down?
Yes, one can change the accelerating voltage without any shut-down. Simply double-click on the voltage display in the upper right-hand corner of the monitor, select a new voltage from the drop-down menu, and set the voltage.