Scanning Electron Microscopy

**This section provides a general description of the page's topic** The Phenom ProX Scanning Electron Microscope can take detailed images of samples. The maximum magnification is 40,000X to 100,000X and the device is capable of resolving features to <500 nm. Samples must be less than 2.5 cm in diameter and less than 3 cm tall.  Additionally, energy-dispersive x-ray spectroscopy (EDX) can be performed on samples for elemental detection through point, line, and area scans.

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Phenom ProX Scanning Electron Microscope

Theory

**This section explains the theory behind scanning electron microscopy**

Phenom ProX Scanning Electron Microscope Standard Operation Procedures

**This section is for the SOP of the particular instrument**

Primary Use

The Phenom ProX SEM offers high resolution images within 30 seconds of sample loading. This device features initial optical imaging to easily navigate around the entire sample. After proper contrast and focus, the operator may alternate to the electron-optical image for higher magnification (up to 100,000x with resolution down to 15 nm). The equipment also comes with EDS (Energy Dispersive Spectroscopy), allowing users to utilize elemental analysis to determine the composition of the sample.

Operating Principle

The SEM produces highly magnified images with a large depth of field. Samples placed within the SEM are scanned with a focused beam of electrons. The electrons are reflected off the sample and collected by a detector, yielding an image. Since heavier atoms will backscatter electrons more strongly than lighter atoms, elements of a higher atomic number will appear brighter. Through EDS, the x-rays emitted from the elements are detected and analyzed to form a prediction of the elemental composition of the sample, and line and map scans can be performed.

Safety Procedures

Samples are prepared by taking a stub and applying carbon tape and then sticking your sample to it. No liquid is permitted in the SEM. Be sure to press your sample onto the carbon tape to make sure nothing is loose. Once that is done, use the compressed air to confirm that there are no loose materials left on the sample. Be sure to wear safety glasses while operating the compressed air, and blow on your sample a couple of times to be sure there is no loose material on your sample. Be sure to securely fasten any ferrimagnets as it might come loose in the chamber.

General Procedure

1. Turning on equipment
   • If the Power LED is yellow, press the power button to wake the SEM up.
   • If two screens are off, turn them on.
   • If the computer on the back of the left monitor is off, turn it on using the button on the right side.
2. Preparing the sample
   • For a sample to be acceptable, it must not be liquid. If it is a ferrimagnet, it must be secured well as to be sure it will not come loose in the chamber. It must be able to be attached to the stub firmly. Compressed air must be used so that no loose material enters the SEM.
   • Put on gloves
   • Get out the stub, sample holder, stub tweezers, normal tweezers, double sided adhesive, and the compressed air.
   • Use the double-sided adhesive on the stub, and then use the normal tweezers to put your sample on the other side of the adhesive tape.
   • Then use the compressed air on your sample. When using the compressed air hold the compressed air can vertically. Do not breathe in the air from the compressed air can. It is toxic.
3. Using the stub holder
   • Use the stub tweezers to put your stub with your sample attached into the sample holder.
   • Turn the knob on the side of the sample holder until the top of the ridge is in line with the top of your sample.
   • Then turn the knob four notches so that ridge of the sample holder is slightly higher than the top of your sample.
4. Putting it in the SEM
   • Open the door to the SEM upwards.
   • Place the sample holder into the SEM with the handle pointing towards you.
   • Close the door to the SEM.
   • Take off the gloves.
5. Optical mode
   • The SEM will create an optical image of the sample. Use the controls in the bottom right of the screen to make the image as clear as possible. The buttons are:
     • The focus tool (the lens) has two modes: auto and manual. In auto mode, an ‘A’ is visible on the button and clicking the button will autofocus the image. In manual mode, the scroll wheel on the mouse or the external metal wheel can be turned to focus the sample. Clicking the button will switch between coarse and fine modes. An ‘F’ is visible on the button in fine mode and movements adjust the focus only slightly. Press and hold the button to switch between modes.
     • The brightness/contrast tool (the sun and contrast symbol) has three modes: auto contrast/brightness, manual contrast, manual brightness. Press and hold the button to switch between auto and manual modes. When in manual mode, press the relevant side of the button to switch between manual contrast and manual brightness. Additionally, in manual mode, the scroll wheel on the mouse or the external metal wheel can be used to adjust the contrast or brightness as needed.
6. Removing the sample from the SEM
   • On the right-hand monitor, click “Eject” from the main screen. Then, click “Okay” and wait a moment to safely remove your sample.
   • Put on gloves.
   • Slide the chamber door up and grab the sample holder by the handle when taking it out.
   • Close the door to the SEM.

For a video playlist with additional explanation of SEM operating procedures click here