1. Common scanning probe modes
Basic mode: surface morphology
Contact mode
Non-contact
Tapping mode
Secondary modes:
Surface potential
Capacitance derivative and actual Capacitance
Surface conductivity
Scanning gate
Magnetic force microscopy
Thermal conductivity and temperature
Trivia: AFM was discovered after the inventor of STM (Gerd Binnig and Heinrich Rohrer were awarded Nobel Prize in1986) wanted to develop a technique for mapping non-conductive samples.

2. Scanning probe microscopy
Atomic force microscopy (AFM) and associated modes: Applicable for conductive and non- conductive samples. Not as high resolution as STM. Best resolution possible in conductive AFM.
Scanning tunneling microscopy (STM): Only applicable for conductive samples. True atomic resolution possible.

3. Picture of a typical AFM machine
A larger view of the system
A close-up of the scanning chamber

4. Parts of an AFM system
A microcantilever to transduce changes in physical parameters
A probe tip to obtain nanoscale resolution
A transduction method to quantify the change in deflection or the oscillation amplitude of the cantilever
Environment control chamber
Noise cancellation schemes
The sample with proper connections

5. Contact mode AFM schematic
Basic idea: In contact mode, the probe tip is in physical contact with the sample, within few Å from the surface, and operates in the repulsive region of the inter-atomic force curve (explained later). In contact mode the cantilever deflection is measured to track the surface morphology using a feedback loop.

6. Non-contact mode AFM schematic
Basic idea: In non-contact mode, the probe tip oscillates in resonance frequency with an amplitude of several tens of nm, and operates in the attractive region of the inter-atomic force curve (explained later). In non-contact mode the oscillation amplitude of the cantilever is measured to track the surface morphology by a feed back loop.
Laser deflection from cantilever sensed with 4 quadrant photo-diode

7. Tapping mode (Intermittent contact mode)
This mode was developed (patented by Veeco Instruments) to take care of some of the problems of both the contact and intermittent contact modes.
Specifically, it takes care of the lateral force problem of the contact mode, and the “water layer sticking” problem of the non-contact mode.
In this mode the tip intermittently comes in contact with the sample and thus can provide much better imaging results, especially in liquid environments.

8. Basics of AFM modes Amplitude Frequency d
Change in amplitude
Curve 2 (near)
Amplitude
Curve 1(far) d
Frequency
Non-contact mode amplitude vs. frequency curve for the tip, far from and near the surface
For van der Waals force region of the F-d curve, the slope dF/dz is positive. Hence 0 decreases as the tip comes closer to the surface, i.e. the curve shifts left

9. Associated modes with contact and non-contact /Intermittent contact modes
Scanning gate (Contact)
Scanning capacitance and capacitance derivative (Contact)
Scanning conductivity (Contact)
Scanning thermal conductivity and temperature (non-contact)
Magnetic force microscopy (non-contact)
Scanning Kelvin probe (non-contact)