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Ramping Using the Force Curve Command: dC/dV – V Spectra

The second method of performing ramps of various SCM signals uses the Ramp menu. A typical application is the measurement of dC/dV–V spectra.

  1. Click the Ramp icon to open the Ramp Parameter list, shown in Figure 1. Ramp parameters are summarized in Table 1.

Figure 1: The Ramp Parameter list window

Parameter Use with SCM
Ramp Output

Select an SCM parameter to ramp:

  • Z (for standard force curve measurements)
  • AC Bias Amplitude
  • Bias Frequency
  • SCM Lock-In Phase
  • DC Bias
  • Capacitance Sensor Frequency
Ramp Begin, Ramp End The beginning and end points of a ramp.
Ramp Rate All ramps are begin-end-begin cycles. Ramp Rate refers to one complete cycle.
Forward Velocity, Reverse Velocity The ramp value from beginning to end, or end to beginning.
X Offset, Y Offset Moves the probe tip to a different location.
Number of samples The number of sample points per ramp (minimum 16, maximum 64,000 for low, < 0.31 Hz, Ramp Rates).
Plot Units Metric or Volts
Feedback Type

Ensures that the deflection feedback is ON during ramping.

Settings:

  • Ramp enables feedback after each ramp cycle (start-end feedback).
  • Cycle enables feedback after each ramp cycle (start-end-start-feedback).
  • Pixel enables feedback after every sample point of the ramp. This is useful for slow ramps with few sample points.
Feedback Counts Select 50 for proper feedback.
Feedback Value Select 0 V.
Dark ramp Enable or Disable. Refer to Dark Lift for details.
Refer to Dark ramp delay Time after laser is turned on.

Table 1: SCM: Ramp Controls Parameters in the Ramp Parameter List Window

NOTE: Ramp Rate, Forward Velocity and Reverse Velocity are interdependent. Changing a velocity affects the overall Ramp Rate, and vice versa.
 
  1. Select the parameter you wish to ramp for Ramp Output.
  2. Select desired values for the other parameters in the Ramp Parameter List window.
  3. Select the desired property (e.g., dC/dV I) for Channel 1,2 or 3 Data Type.
  4. Start or stop ramping by clicking the associated toolbar button (see Figure 2). 

Figure 2: Toolbar Buttons: Start, Stop and Capture Ramp Curves

 

  1. Capture ramping curves using the standard Capture commands or toolbar buttons.

 

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