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PeakForce QNM Control Parameters

Peak Force Amplitude

The zero-to-peak amplitude of the cantilever drive in the Z axis (Z modulation). Increasing Peak Force Amplitude will reduce the contact time during each tip tapping cycle on the sample and help tracking the rough and/or sticky sample by avoiding a situation where the tip is unable to pull off from the sample. Reduced Peak Force Amplitude is desired in liquid on flat samples. Less Peak Force Amplitude results in less hydrodynamic force disturbance.

Peak Force Frequency

The frequency of the Z-axis modulation. Lower tapping frequencies may be useful for fluid imaging and also allow for time-dependent experiments.

Settings:

Lift Height

The distance that the Z-piezo is retracted from the sample during an Auto Config operation.

NOTE: Changing the Lift Height will automatically start the Auto Config function (See Optimizing a ScanAsyst Image) and retract the Z piezo to the specified Lift Height. Clicking Auto Config will automatically calculate the Lift Height and perform an Auto Config operation.

Maximum Force Fit Boundary

The Max Force Fit Boundary of the unload force curve, shown in Figure 1, is excluded from the DMT Modulus calculations.

NOTE: A smaller Max Force Fit Boundary means that less region of the force curve is excluded from the DMT modulus calculations.

Range and Settings:

  • 0–100%.
  • Typical: 90%.

Figure 1: DMT Fit regions of the Force curve

Minimum Force Fit Boundary

The Min Force Fit Boundary of the force curve, shown in Figure 1, is included in the DMT Modulus calculations.

Range and Settings:

  • 0–100%; 100% is defined as the force between the adhesion point and the peak force.
  • Typical: 30%.

The portion of the force curve between the Max Force Fit Boundary and the Min Force Fit Boundary is included in the DMT Modulus calculations. For typical numbers discussed here, the region between 90% and 30% of the unload force curve will be included in the DMT modulus calculations.

Deformation Force Level

The Deformation Force Level of the load force curve, shown in Figure 2, is excluded from the Deformation channel display. This parameter is used to reduce the effect of baseline noise.

Range and Settings:

  • 50–100%; 100% is defined as the force between the zero force point and the peak force in the load curve.
  • Typical: 15%. The portion of the force curve above the 15% point is displayed in the Deformation channel.

Figure 2: DMT Fit regions of the Force curve

 

 

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