OhioMod2013:Methods/AFM
Atomic Force Microscopy
Atomic Force Microscopy (AFM) uses a cantilever with a sharp probe to scan the surface of a sample. When in contact to the surface interaction, the probe imposes bending to the cantilver, which can be measured using a laser beam that is deflected off of the cantilever.
One mode of the AFM is the intermittent contact mode in which the cantilever is oscillated in a particular resonance frequency. When the probe is in close contact with the sample, the amplitude of the resonance changes and can be measured. This method is what we used due to its ability to measure weakly adhered nanoparticles. Eventually a topographic image can be generated of the specimen. Keep in mind that the lateral dimensions of the particle are influenced by the shape of the probe, but hte height measurement can be well coressponded to the diameter size.
I will be using the Alysum MFP-3D system. See website [1] and probe [2]
- Three switches to turn on: the computer tower key, the lamp switch, and the Herzam raised floor.
- Push E button on Herzam as well.
- When inserting the head of the AFM onto the stage, insert one prong in at a time, with the last prong inserted facing you, thus tilting it in. CAREFUL!!!
- There are a variety of knob discs for which to raise and lower the head on the stage.
- Username: MFP3D password: data
- Make sure both 'ready' icons are on when software started.
- The right monitor can be changed to different channels. Channel 3 = AFM optical camera.
Adjust laser
- Can adjust the laser position along the cantilever.
- For sum: aim for 4-5
- For deflection: aim for 0
- Can use autotune to scan natural frequency.
- The default amplitude we use is 1V.
- Engage Z-voltage.
- Set to 1 V amplitude for when cantilever is free.
- Lower until you see 0.9 V. Close doors, and use only the window door now.
- Continue lowering until 0.8 V. The Z-voltage will now continue to adjust to make sure it stays above 0.8 V. You can lower to watch as the Z-voltage decreases.
- Default settings for scanning: 20 micron area
- Adjust the integral gain, proportional gain, and set point for when you are scanning.
- When you withdraw, use the height knob around 20 spins to make sure it is raised at a high height for the next user.
