Software Selection

Click the Select Experiment icon in the NanoScope toolbar. This opens the Select Experiment window, shown in Figure 1.

Figure 1: The Select Experiment, TUNA mode, window.

Select Electrical & Magnetic in the Experiment Category panel.

Select Application Modules in the Experiment Group panel.
Select Tunneling Current AFM (TUNA2 module) in the Select Experiment panel.
Click the Load Experiment button.
The Feedback and TUNA panels, shown in Figure 2, in the Scan Parameter list display the TUNA control parameters.

Figure 2: TUNA control parameters in the Scan Parameter list

NOTE: If you have PeakForce Qnm and TUNA, there is an additional mode PeakForce TUNA.

NOTE: If you have Torsional Resonance and TUNA, there is an additional mode. Refer to TUNA and TR Mode for details.

Bruker recommends performing TUNA measurements in open loop mode only. (For information about TUNA measurements in closed loop mode, refer to Closed Loop TUNA Imaging). Select a DC bias and measure the current passing through the sample. The Scan Parameters relevant to TUNA are shown in Table 1.

Parameter	Use with TUNA
Feedback Mode	Disabled: open loop. Enabled: closed loop. For TUNA, select Disabled.
Current sens	Selects the gain of the TUNA sensor: 1pA/V = gain of 1012 10pA/V= gain of 1011 1nA/V = gain of 109 100nA/V = gain of 107
DC Test Bias	Provides an additional bias for the purpose of testing the TUNA sensor.
DC Sample Bias	Selectable bias to chuck/sample.
Bias Upper Limit	Limits the maximum bias applied to the chuck/ sample in closed loop mode.
Bias Lower Limit	Limits the minimum bias applied to the chuck/ sample in closed loop mode.
Feedback Igain	Integral gain used for closed-loop mode.
Feedback Setpoint	Not used in open loop mode. Selects the current setpoint in closed loop mode.

Parameter

Use with TUNA

Feedback Mode

Disabled: open loop. Enabled: closed loop. For TUNA, select Disabled.

Current sens

Selects the gain of the TUNA sensor:

1pA/V = gain of 1012
10pA/V= gain of 1011
1nA/V = gain of 109
100nA/V = gain of 107

DC Test Bias

Provides an additional bias for the purpose of testing the TUNA sensor.

DC Sample Bias

Selectable bias to chuck/sample.

Bias Upper Limit

Limits the maximum bias applied to the chuck/ sample in closed loop mode.

Bias Lower Limit

Limits the minimum bias applied to the chuck/ sample in closed loop mode.

Feedback Igain

Integral gain used for closed-loop mode.

Feedback Setpoint

Not used in open loop mode. Selects the current setpoint in closed loop mode.

Table 1: TUNA Control parameters

NOTE: Due to inherent mechanical characteristics of the specialized probe holder necessary for this imaging mode, reduced closed loop X IGain and Y IGain parameters are necessary.

Select Calibrate > Scanner > X-Y... from the main menu. The OptoXY Closed Loop Calibration dialog will open.
Set X IGain and Y IGain to 8.
Click OK to close the window and continue with your experiment.

Ensure that you reset the parameters to their default values (12) when using the standard air tapping or TR holder.

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	Select Electrical & Magnetic in the Experiment Category panel.
	Select Application Modules in the Experiment Group panel. Select Tunneling Current AFM (TUNA2 module) in the Select Experiment panel. Click the Load Experiment button. The Feedback and TUNA panels, shown in Figure 2, in the Scan Parameter list display the TUNA control parameters.