Atomic Force Microscopy - Sideversjonshistorikk

Ingrhal: /* Modes of operation */

2009-05-26T15:06:27Z

Modes of operation

← Eldre sideversjon		Sideversjonen fra 26. mai 2009 kl. 15:06
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	==Modes of operation==		==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.		It is the displacement of the probe tip at the end of the cantilever that is measured. The modes use different tips, and therefore have different resolutions. Problem and material determines which mode is used.

	Interaction model (surface forces) lies behind different modes:		Interaction model (surface forces) lies behind different modes:
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	===Contact mode===		===Contact mode===
	In the contact region of the potential energy curve, repulsive forces dominate.		In the contact region of the potential energy curve, repulsive forces dominate. The tip most commonly used is silicion nitrid, because of its physical restitance to damage. The radii is about 20-60nm, and atomic resolution is therefore beyond reach.

	Two sub-modes:		Two sub-modes:
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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. Force on probe tip changes sign during cycle. Phase image extremly sensitive to elastic properties.		In the semi-contact region of the potential energy curve. Attractive and repulsive forces have similar magnitude. Force on probe tip changes sign during cycle. The tip used is usually a silicon tip with radii in the order of 10nm, which result in a very high resolution. Phase image extremly sensitive to elastic properties.

	===Non-contact mode===		===Non-contact mode===

Fredrimu: /* Contact mode */

2009-05-26T11:42:48Z

Contact mode

← Eldre sideversjon		Sideversjonen fra 26. mai 2009 kl. 11:42
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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.

	Two sub-modes:		Two sub-modes:

Fredrimu: /* Short facts */

2009-05-26T11:28:56Z

Short facts

← Eldre sideversjon		Sideversjonen fra 26. mai 2009 kl. 11:28
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	*Piezoelectric position control system.		*Piezoelectric position control system.
	*The cantilever: V-shaped or single beam. V-shaped: high deflection sensitivity, not sensitive to torque. Single beam: vice-versa.		*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.		*Tip materials used: diamond, tungsten, silicon. Silicon nitride - high elastic rigidity.
	*Artifacts: drift, non-linear hysteresis of piezoelectric.		*Artifacts: drift, non-linear hysteresis of piezoelectric.

Fredrimu: /* Tapping mode */

2009-05-24T12:34:40Z

Tapping mode

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 12:34
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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. Force on probe tip changes sign during cycle. Phase image extremly sensitive to elastic properties.

	===Non-contact mode===		===Non-contact mode===

Fredrimu: /* Contact mode */

2009-05-24T11:26:47Z

Contact mode

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 11:26
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	*Set height constant and measure repulsive force.		*Set height constant and measure repulsive force.
	*Set repulsive force constant and measure height.		*Set repulsive force constant and measure height.

			Artifacts that can be removed when operating in contact mode:
			*Capilliary attraction from films of moisture (under atmospheric conditions).
			*Electrostatic charging of surface

	===Tapping mode===		===Tapping mode===

Fredrimu: /* Modes of operation */

2009-05-24T11:24:11Z

Modes of operation

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 11:24
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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.

			Maximum deflection sensitivity: Thin v-shaped cantilever. Si nitride tip minimizes damage to the tip. Soft samples: Constant pre-set cantilever deflection. (Kan noen utdype/omformulere siste setning?)

	[[Kategori: teknikker i tools]]		[[Kategori: teknikker i tools]]

Fredrimu: /* Basic setup and components */

2009-05-24T11:15:56Z

Basic setup and components

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 11:15
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	*Solid state laser		*Solid state laser
	*The deflected cantilever reflects a laser beam from two points on the cantilever (before and after deflection) and two beams are sent to the detector. The signal generated depends on the proporiton of light falling on each half of the photodiode. (Noen som kan forklare dette bedre?)		*The deflected cantilever reflects a laser beam from two points on the cantilever (before and after deflection) and two beams are sent to the detector. The signal generated depends on the proporiton of light falling on each half of the photodiode. (Noen som kan forklare dette bedre?)
			*Can also measure phase shifts.

			Data collection:

			*Artifacts! Non-linearity in piezoelectric response. Sample surface must be coplanar with x-y scan of probe tip.

	==Modes of operation==		==Modes of operation==

Fredrimu: /* Basic setup and components */

2009-05-24T11:10:55Z

Basic setup and components

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 11:10
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	*X-Y: Applying voltage of opposite signs across diagonal segments of piezoelectric tube. Will cause it to bend.		*X-Y: Applying voltage of opposite signs across diagonal segments of piezoelectric tube. Will cause it to bend.
	*Z: Apply voltage on tube that contracts or expands axial length.		*Z: Apply voltage on tube that contracts or expands axial length.

			Split photo detector:

			*Solid state laser
			*The deflected cantilever reflects a laser beam from two points on the cantilever (before and after deflection) and two beams are sent to the detector. The signal generated depends on the proporiton of light falling on each half of the photodiode. (Noen som kan forklare dette bedre?)

	==Modes of operation==		==Modes of operation==

Fredrimu: /* Basic setup */

2009-05-24T11:02:05Z

Basic setup

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 11:02
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	*Artifacts: drift, non-linear hysteresis of piezoelectric.		*Artifacts: drift, non-linear hysteresis of piezoelectric.

	==Basic setup==		==Basic setup and components==

	*AFM often mounted on rigid base with high damping capacity.		*AFM often mounted on rigid base with high damping capacity.

Fredrimu: /* Fun facts */

2009-05-24T11:01:33Z

Fun facts

← Eldre sideversjon		Sideversjonen fra 24. mai 2009 kl. 11:01
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	==~~Fun~~ facts==		==Short facts==
	*High vacuum is not necessary.		*High vacuum is not necessary.
	*Piezoelectric position control system.		*Piezoelectric position control system.