AFM AC Tips and Tricks
MIME Oregon State University
AFM
­ AC mode Tips and
tricks
This Manual Does Not Replace the Manufactures Manual and/or Proper Training!
01/24/2015
Austin Fox (​
AustinFoxMaterials@gmail.com​
) Please email with questions :)
Page 1 Licensed CC BY 4.0
AFM AC Tips and Tricks
MIME Oregon State University
Quick guide to how AC mode works
Shown here are the effects of changing parameters or moving over a sample feature.
This is under normal running conditions with no adjustments to the head height.
Voltage​
- measured oscillation (vibration) of the tip.
Z-Voltage (ZV)​
- voltage applied to the piezo adjusting tip height,↑V = away from sample.
Drive Frequency (DF)​
- tip oscillation frequency.
Set Point (SP) ​
- Voltage maintained by adjusting the z-voltage (surface force)
(damping the oscillation). ↓ Set Point ↑ Force on surface
Drive amplitude (DA)​
- is the voltage applied to oscillate the tip.
Works opposite of Set point. ↑ Drive Amp ↑ Force on surface
Gain​
- response time of the z-voltage. Too high = ringing and too low = no trace.
Phase​
- the difference between the input and output signals.
Make a experiment file (.pxp)...
● It saves your workspace, settings, and save location (yes, you can change it!)
● Don’t select a mode on start up; just open your experiment file...
01/24/2015
Austin Fox (​
AustinFoxMaterials@gmail.com​
) Please email with questions :)
Page 2 Licensed CC BY 4.0
AFM AC Tips and Tricks
MIME Oregon State University
Tuning Parameters
Attractive mode
For ‘Soft’ Samples
Use Lower Free Air Amp (0.3V)
Image at > ‘free air’ phase
High Q
↑ Set Point/ Free Air Amp
Larger tip radius
Set f +10% f​
(right of Resonance)
o​
Repulsive mode
What we normally use
Use Higher Free Air Amp (1V)
Image at < ‘free air’ phase
Low Q
↓ Set Point/ Free Air Amp
Smaller tip radius
Set f -8% f​
(left of Resonance)
o​
Max Band Width (Max Scan Rate)
Sample Speed must be < Collection Limit to achieve good quality scans. If it is not, do
a “One Tune” decreasing the Qgain by -0.01.
If not:
Add increments of -0.01 to the Qgain
Then “One Tune” – Recalc CL
Phase Hopping ​
(red-blue..)
Or tip not seem tracing well
Increasing the DA may help (doubling will often stabilize the phase):
● Just jump up the DA or;
● Save the tip by;
o Withdrawing the tip → doing the increase → Re-engage
● Try up to 4x
● Gain will need to be decreased to account for increase in DA
Mounting Your Sample
● Reduces drift
○ Fewer but better contacts
○ Lower chance of air bubbles
● Makes removal easier
01/24/2015
Austin Fox (​
AustinFoxMaterials@gmail.com​
) Please email with questions :)
Page 3 Licensed CC BY 4.0
AFM AC Tips and Tricks
MIME Oregon State University
Hot Keys
Crtl+ I- Igor A&B cursors Crtl+ A- Rescale
Crtl+ F- search in the global variables Crtl+T – Igor Tool box
Crtl + W- closes forward most window Crtl+ D – duplicates forward-most window
Crtl+C- copy Crtl+V- paste
Crtl+ Y- window control- can rename windows Crtl+O- open experiment
Crtl+P- print Crtl+L – load waves
Crtl+J- bring History window forwardmost Crtl + 1- Windows Manager
Crtl+ 2- Do thermal Crtl+3- single force pull
Crtl+4- cantilever auto tune Crtl+6- open S&D meter
Crtl+7- open Master Channel Panel Crtl+8- open NAP channel stuff
Crtl+9- open NAP panel Crtl+ F1- Igor search panel
Crtl+F2- open Mode Master Crtl+M – opens Igor Procedure window
Finding the Laser
Center LD X and Y (8 turns from end)
● Laser will be on tip within 1turn
● Turn =
○ Finger on side opposite of rotation direction
○ Rotate until finger hits other side ≈180°
Deflection
As Shown turn the PD nob:
● Toward the back of the head to make the deflection more negative
● Toward the front to make more positive
Do Not ever​
force the PD nob - it can cause ​
serious damage!
Save your tip!!!
Load It Properly and Let It Equilibrate!!
1.
2.
3.
4.
Load tip as shown to the below
Load sample and place head (take care not to crash tip!)
Align laser spot toward end of cantilever and zero deflection
Do “Auto Tune”, -8% f​
o
a. Check achievable scan rate
5. Let sit for 10+ mins (equilibrate)
6. Re-zero Deflection
7. Do “Auto Tune”, -8% ​
f​
o
a. Check achievable scan rate
8. Soft Engage
01/24/2015
Austin Fox (​
AustinFoxMaterials@gmail.com​
) Please email with questions :)
Page 4 Licensed CC BY 4.0
AFM AC Tips and Tricks
MIME Oregon State University
Soft Engage!
1)
2)
3)
4)
Perform an Auto Tune.
Set the Set Point voltage to 950 mV
Click ‘Engage’ button
Slowly turn the front thumbwheel CCW (Lowering the head)
a) Monitor the amplitude voltage (S&D meter)
b) Waiting for it to equal the Set Point voltage
i) This is a false engagement (Engaging water layer…)
c) Lowering the head until ZV is about 40V (halfway blue)
i) You’ll notice the ZV seems to float/drift as you move the thumbwheel- that’s
because it’s falsely engaged!
5) With the radio label for the Set Point voltage activated use the ‘Hamster’ wheel on
front of controller to increase the force
a) The ZV will move to some more positive voltage value (more red)
i) At some point you’ll notice the ZV will no longer quickly become more
positive (It may still slowly get more positive)
6) At this point, the tip is ‘hard’ engaged on the surface
7) Using the thumb wheel adjust the ZV to ≈50V to achieve 70V after reengage
8) Withdraw or increase set point to pop tip of surface and lower door
Adjust Gain!
● Increase until you see ringing
● Decrease to get ringing to go away
● Saves tip by optimizing the gain, minimizing the chance that the tip will crash into
a large feature
Tip Motion
Tip can be moved from -40μm to +40μm or do an 80μm scan max
I don’t know if the image below is correct. I need to check!!!
01/24/2015
Austin Fox (​
AustinFoxMaterials@gmail.com​
) Please email with questions :)
Page 5 Licensed CC BY 4.0