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EDS Operations:
SEM Operating Instructions:
Preparing a Sample
• Before any work may be done with the EDS one must first properly mount the sample in the SEM for viewing
• Sample mounts are available at the SEM station for general public use. If you require special characteristics(slope, etc.), or desire your own mount, it is your responsibility to have a machine shop prepare one that has the correct dimensions to fit the holder (see manual).
• The sample's dimensions should not exceed 150 mm in diameter.
• If your sample is non-conductive it is recommended, but not required, to sputter gold onto the sample for proper viewing.
• The sample should be attached using the carbon tape provided
• When you sample is properly attached to the mount use the height-restriction marker to ensure that your sample is short enough to clear the SEM's working parts. If your sample is too tall and you attempt to place it into the chamber, you will damage the machine! Keep in mind that if your sample is relatively large and you plan on tilting it the tallest point on the sample will shift will be along the edge. You should adjust the z-axis appropriately to ensure the clearance before you tilt the sample.
Venting
Anytime the chamber is opened or pumped down one must ensure that the sample holder is in the exchange position. The exchange position settings for the four axes are listed on the side of the chamber. Moving the sample holder into or out of the chamber when it is not in the exchange position may damage the machine!
1. Once the exchange position is set, check the SEM software to make sure that no voltage is applied to the filament. If there is a voltage applied, turn it off by clicking on the HV button.
2. Press the EVAC button on the front of the SEM to begin venting.
3. You will see the pressure gauge on the screen move from blue to red as the pressure increases in the chamber. Once the gauge's bar disappears, allow approximately 30 more seconds before attempting to open the chamber.
4. Gently open the chamber. You should have to apply very little if any force to open the chamber if it is at atmospheric pressure.
Loading the sample holder
With the sample properly mounted and the chamber vented, the mount may now be placed into the holder.
1. The mount should slide easily into the holder's orifice. If there is resistance, check that there is no obstruction inside the orifice or debris on the mount's walls. If it still does not slide easily ask for help from an experienced user or contact the equipment trainer.
2. While watching the tallest point of the sample to ensure clearance of the SEM's internal workings, slowly slide the chamber closed.
Pumping
While holding the chamber door closed, press the EVAC button to begin pumping the chamber.
1. The pump will engage and seal the chamber door.
2. The progress of the pumping may be seen on the on-screen pressure gauge. While the chamber is pumping the gauge will be red to indicate the incomplete vacuum in the chamber. The bar will then become green when the chamber is pumped and is being prepared for use. When the bar becomes blue the system is ready for use.
Developing an Image
With the chamber pumped to operating pressure one may now configure the SEM.
1. The accelerating voltage may be set by right-clicking on the voltage display. See the manual for the particulars of choosing the best voltage for your purposes. Approximately 10-15 kV is a good starting point if you are unsure of what voltage would be best.
2. Click the HV button to apply the voltage and begin viewing your sample. If no current is displayed when a voltage is applied the filament is burned out and will need replacement. Please contact the technical office so that the proper steps can be taken.
3. With the voltage applied you are now ready to view the sample. You may adjust the position of your sample with the sample holder adjustment dials on the front of the chamber. The focus and zoom may be controlled from the small panel in front of the screen. The SEM software is also available to make fine adjustments of viewing parameters (please see the manual for details).
4. For EDS operations, develops a clear image at or higher than 1000x Magnification.
EDS Operating Instructions:
Setup
With Sample loaded and image developed on SEM lower the EDS probe into EDS viewing position.
1. Log into EDS through wall mounted access controller mounted on the wall left of the SEM.
2. Open up Spectra Plus software located on EDS computer desktop. When Spectra Plus is up and running open up the Setup tab, at the top of the screen, and adjust process time between 60 and 90 seconds. While still on the Setup tab, make sure the EDS is in classic mode.
PHA Status
Adjust the PHA Status by opening up the PHA Status tab under Acquisition, located at the top of the Spectra Plus software
1. Detects should be around 1800 and % Deadtime should be between 14 and 18 percent. To adjust Detects and Deadtime one need to adjust the Working Distance, Aperture, Current, or Voltage on the SEM.
2. Changing the working distance should always be one's first adjustment. Decrease working distance until the PHA Status reaches its operational range or the working distance reaches 15.
3. To open the aperture one needs to rotate the large silver aperture knob protruding from the SEM tower. One counter-clockwise motion will open the aperture one step (from 3 to 2). If the PHA Status exceeds its working limit after opening the aperture try increasing the working distance to achieve the proper PHA Status.
4. If adjustments are still needed to the PHA Status Increase the Voltage. The accelerating voltage may be adjusted by right-clicking on the voltage display. Increase the voltage until the PHA Status reaches it operational range or the accelerating voltage reaches 20Kv.
5. If the PHA Status has still not met operational range increase the SEM's current. The SEM's current can be adjusted by right-clicking on the voltage display on the SEM. Slowly adjust the current slider located below the voltage selector in the tap. CAUTION: Adjusting the SEM's current should only be performed by experience users and then only as a last resort action.
Collecting Data
With Setup and PHA Status configured click the go button to begin collecting data.
1. The graph located on the screen will begin to fill with data and the time is counted down in the upper right hand corner. Click the up arrow located at the top of the screen to autoscale the graph.
2. When the EDS completes its data acquisition it is now possible to label the data. To record the elements collected one can either label them manually with Identify Manual and the provided periodic table or have the EDS do it with Identify Auto. Both buttons are located at the top of the Spectra Plus software.
-Identify Auto will identify portions of the scan with elements that are as close to the measure value, but are not always the exact element, use the periodic table provided to double check the possible makeup of the sample.
Quantifying Data
With the graph labeled it is now possible to record the atomic properties of the sample.
1. Open up Quantify How, located under the Quantify tab. click the "get id list" button, located towards the bottom of the window, to populate the element list in the middle of the window.
2. One may now add or remove elements from the list to quantify.
3. Next click the Quantify Now button, located under the Quantify tab. This will quantify the percent compositions of the atoms selected and display their results on the second tab below the graph.
Saving Data
Once the data has been quantified it is possible to save all data for printing
1. To save all information, click the HTML Report button located under the File tab. This will prompt you to save your information under the G: drive. Name your file and click ok.
2. You can retrieve your file under the Noran EDS System link at http://grover.mirc.gatech.edu/equipment/displayFileIndex.php