Voltage preamplifier for extensional quartz sensors used in scanning force microscopy.

Extensional-mode quartz resonators are being increasingly used as force sensors in dynamic scanning force microscopy or atomic force microscopy (AFM). We propose a voltage preamplifier in order to amplify the charge induced on quartz electrodes. The proposed solution has some advantages over the typically used current-to-voltage converters. First, the gain does not depend on the inner parameters of the quartz resonator, which are usually unknown for the specific resonator and may even vary during the measurement. Second, with such an amplifier a better signal-to-noise ratio can be achieved. Finally, we present AFM images of the Si(111) and the SiO(2) surfaces obtained by the voltage preamplifier with simultaneously recorded tunneling current.