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Unformatted text preview: Servo Dialog Box The Servo dialog box controls the scanner's Z (vertical) servo. Open the dialog box by clicking the Imaging toolbar button . The Scan and Motor and Realtime Images dialog boxes will also open. Main tab Advanced tab Servo Tips Servo Dialog Box Main Tab Off Selecting this check box disables the feedback loop controlling the height of the tip. The Z height of the tip will remain constant as it scans. When the servo is off, the tip is vulnerable as sample features of sufficient height may contact and damage the tip. Therefore, only check this box if the sample is well known and free of large discontinuities. I and P Gains (%) The I (Integral) and P (Proportional) Gain coefficients dictate how quickly the system will react to changes in deflection or amplitude as the tip scans the surface. I and P are factors of the Z scanner voltage (Vz), which is proportional to the height of the scanner above the adjusts Vz to keep the tunneling current, deflection or amplitude (depending on the Imaging Mode ) as close t possible. Vz is more sensitive to changes in Integral Gain than Proportional Gain. If the gain settings are too low, the scanner will not react to topographical changes quickly, resulting in blurre gain is too high, the scanner will oscillate around the true height of the sample, resulting in inaccurate imagin to the tip.You can use Smart Index Controls to adjust this parameter. Tips on setting the I and P Gains . Setpoint The Setpoint is the value of the tunneling current, deflection or amplitude that the system tries to maintain for Mode . The units will change depending on the mode. You can use Smart Index Controls to adjust this param Tips on adjusting the Setpoint . Sample/Tip Bias This is the electric potential between the sample and the tip. This control is labeled "Sample Bias" or "Tip Bia setting on the Advanced tab . The value can be set from -10 to 10 volts. You can use Smart Index Controls to Range This is the range of motion of the Z servo, in microns. Reducing the servo range increases the Z resolution o image. This does note clip the actual Z movement of the tip but instead reduces the range of data values thaimage....
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This note was uploaded on 09/08/2010 for the course MATE 145 at San Jose State University .