TITLE:
Compensation of Parasitic Capacitance of Quartz Tuning Fork in AFM
AUTHORS:
Yidai Liu
KEYWORDS:
Atomic Force Microscope, Quartz Tuning Fork, Stray Capacitance, Compensator Circuit, PDMS Sample
JOURNAL NAME:
Journal of Applied Mathematics and Physics,
Vol.11 No.5,
May
30,
2023
ABSTRACT: We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this report, we demonstrated a simple but effective method to compensate for this parasitic capacitance by adding a compensator circuit consisting of an inverting amplifier and a capacitor. The capacitor is connected in series with the inverting amplifier and the compensator is connected in parallel with the quartz tuning fork. The resonance curve of the system measured after adding the homemade compensator resembles that of a pure RLC circuit, meaning that the stray capacitance is successfully eliminated. Furthermore, we tried to use our equipment to measure PDMS sample and got clean data. This system can be further combined with confocal microscope and diamond with NV defect to build scanning NV magnetometry.