A Signal Preamplifier of the Piezoelectric Vibration Transducer of the Cantilever of an Atomic-Force Microscope

Abstract

An electronic circuit for amplitude and phase measurements of the forced vibrations of the tip of the scanning atomic-force microscope by the current flowing through the piezoelectric cell exciting these vibrations is described. The circuit allows the electronic correction of the Q factor (width of the resonance peak) of the driven oscillatory system tip-piezoelectric cell (for example, a crystal tuning fork), and, as a result, reduction by a factor of 2-50 of the settling time of the parameters of tip vibrations reflecting its interaction with the studied surface. The output signal of the described circuit corresponds to the current through the piezoelectric cell. Due to the proposed correction of the capacitive component of the piezoelectric cell's current, the phase range of the output signal observed upon attainment of the tuning-fork resonance frequency has increased from several degrees to a 180° theoretically expected value.

Voltage preamplifier for extensional quartz sensors used in scanning force microscopy

“…This effect can be minimized by using various electronics designs, such as a resistor network, a compensated capacitor, 23 the double amplifying stages, 24 a bridge circuit, 25 or the feedback active parts. 26,27 Nevertheless, they introduce additional noise and the precisely determined values of passive parts are often required. In order to avoid a gain reduction as well as a complex design, we propose a one-stage voltage amplifier (VVa) to intensify the quartz signal.…”