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Ramp Panel

Control Description

Ramp Output

Specifies the Ramp Channel.

Ramp size

Specifies the range of the Ramp Channel. Visible only if the Ramp Channel parameter is set to Z. Settings depend on the specified units.
Ramp Begin Specifies the start of the Ramp Channel scan. Units depend on the setting for Ramp Channel.
Ramp End Determines the end position of the output ramp.

Z scan start

Visible only if the Ramp Channel parameter is set to Z and Trigger Mode is Off. Z scan start is the bottom position of the Z-axis scan as represented on the Real Time status bar. When the Ramp node is first accessed during imaging, this value is automatically set to the Z Center Position.

Range and Settings:

  • The range of this parameter depends on the scanner. The units of this parameter are volts or nanometers, depending on the setting of the Units parameter.
NOTE: The value of this parameter will need to be increased to move the sample closer to the cantilever in the case where there is no deflection of the cantilever for a displacement of the sample.
NOTE: While the user is ramping Z in Ramp Mode, some feedback parameters are inactive.

Ramp Rate

The Ramp Rate sets the ramping rate. Changing this value effects the Forward and Reverse Velocities.

Forward Velocity

Forward Velocity of the tip (in µm/s) as it approaches the surface. Increasing this value increases the Ramp Rate.

Reverse Velocity

Reverse Velocity of the tip (in µm/s) as it retracts from the surface.

X Offset

Controls the position of the range in the X direction.

Y Offset

Controls the position of the range in the Y direction.

Number of samples

Number of data points collected during each upward (retraction) and downward (extension) travel cycle of the piezo. The Number of samples parameter sets the pixel density of the force curve. This parameter does not change the Z scan size.

Range or Settings:

  • 16 to 19,968 data points displayed per extension and retraction cycle.
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.
Feedback Counts Specifies the amount of time (in DSP interrupt cycles, ~25 ms) that feedback will be on. Allows sufficient time for the control system to settle. A Feedback Counts value greater than 1000 is recommended.
Feedback value

Specifies the bias voltage at which feedback runs to achieve the Current Setpoint.

NOTE: Feedback value is useful only in scanning tunneling microscopy (STM) and allows adjustment of the feedback value to a different bias than is being used in Image Mode.

Spring Constant

Records the spring constant of the cantilever that is currently being used. This parameter is input by the user and is recorded along with each force plot captured. It is used for Offline analysis of the force plot. It is not critical to set the Spring Constant in Realtime, since it can be altered in the Offline analysis of the captured force plot. The Spring constant is necessary to display a graph of force vs. separation if Units is set to Force.

Plot Units

Switches parameters in the control panels between units of Volts (V), Metric (nm or µm), or Force (nN). Changing this parameter also changes the setting of the Units parameter on the Scan Parameter panel.

Range or Settings:

  • Volts (V),
  • Metric (nm)
  • Force (nN)

Display Mode

The portion of a tip’s vertical motion to be plotted on the force graph.

Range or Settings:

  • Extend—Plots only the extension portion of the tip’s vertical travel.
  • Retract—Plots only the retraction portion of the tip’s vertical travel.
  • Both—Plots both the extension and retraction portions of the tip’s vertical travel.
  • If a channel other than Z is chosen, Display Mode will not be available in Offline view.

X Rotate

Allows the user to move the tip laterally, in the X direction, during indentation. This is useful since the cantilever is at an angle relative to the surface. One purpose of X Rotate is to prevent the cantilever from plowing the surface laterally, typically along the X direction, while it indents in the sample surface in the Z direction. Plowing can occur due to cantilever bending during indentation or due to X movement caused by coupling of the Z and X axes of the piezo scanner. When indenting in the Z direction, the X Rotate parameter allows the user to add movement to scanner in the X direction. X Rotate causes movement of the scanner opposite to the direction in which the cantilever points. Without X Rotate control, the tip may be prone to pitch forward during indentation. Normally, it is set to about 22.0º.

Range or Settings:

  • 0 to 50º; most effective values are between 15 and 25º.

 

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