Forskjell mellom versjoner av «Atomic Force Microscopy»
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| − | + | ==Fun facts== |
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*High vacuum is not necessary. |
*High vacuum is not necessary. |
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*Piezoelectric position control system. |
*Piezoelectric position control system. |
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| Linje 6: | Linje 6: | ||
*Artifacts: drift, non-linear hysteresis of piezoelectric. |
*Artifacts: drift, non-linear hysteresis of piezoelectric. |
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| − | + | ==Modes of operation== |
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It is the displacement of the probe tip at the end of the cantilever that is measured. The modes have different resolution (can someone explain this?). Problem and material determines which mode is used. |
It is the displacement of the probe tip at the end of the cantilever that is measured. The modes have different resolution (can someone explain this?). Problem and material determines which mode is used. |
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| Linje 12: | Linje 13: | ||
*Strongly affected by surface adsorbates and gaseous/liquid environment. |
*Strongly affected by surface adsorbates and gaseous/liquid environment. |
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| − | ==Contact mode== |
+ | ===Contact mode=== |
In the contact region of the potential energy curve, repulsive forces dominate. This mode has the highest resolution. |
In the contact region of the potential energy curve, repulsive forces dominate. This mode has the highest resolution. |
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| Linje 19: | Linje 20: | ||
*Set repulsive force constant and measure height. |
*Set repulsive force constant and measure height. |
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| − | ==Tapping mode== |
+ | ===Tapping mode=== |
In the semi-contact region of the potential energy curve. Attractive and repulsive forces have similar magnitude. |
In the semi-contact region of the potential energy curve. Attractive and repulsive forces have similar magnitude. |
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| − | ==Non-contact mode== |
+ | ===Non-contact mode=== |
In the non-contact region of the potential energy curve, attractive forces dominate and are measured. What is observed is a an increase in the amplitude of the oscillations of the vibrating probe, translated into a change in attractive forces. |
In the non-contact region of the potential energy curve, attractive forces dominate and are measured. What is observed is a an increase in the amplitude of the oscillations of the vibrating probe, translated into a change in attractive forces. |
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Revisjonen fra 24. mai 2009 kl. 12:37
Fun facts
- High vacuum is not necessary.
- Piezoelectric position control system.
- The cantilever: V-shaped or single beam. V-shaped: high deflection sensitivity, not sensitive to torque. Single beam: vice-versa.
- Material used: diamond, tungsten, silicon.
- Artifacts: drift, non-linear hysteresis of piezoelectric.
Modes of operation
It is the displacement of the probe tip at the end of the cantilever that is measured. The modes have different resolution (can someone explain this?). Problem and material determines which mode is used.
Interaction model (surface forces) lies behind different modes:
- Strongly affected by surface adsorbates and gaseous/liquid environment.
Contact mode
In the contact region of the potential energy curve, repulsive forces dominate. This mode has the highest resolution.
Two sub-modes:
- Set height constant and measure repulsive force.
- Set repulsive force constant and measure height.
Tapping mode
In the semi-contact region of the potential energy curve. Attractive and repulsive forces have similar magnitude.
Non-contact mode
In the non-contact region of the potential energy curve, attractive forces dominate and are measured. What is observed is a an increase in the amplitude of the oscillations of the vibrating probe, translated into a change in attractive forces.
