Signal electronics for an atomic force microscope equipped with a double quartz tuning fork sensor

Signal electronics equipped with a bandpass filter phase detector for noncontact atomic force microscopy (ncAFM) has been developed. A double quartz tuning fork assembly is used as a force sensor, where one fork serves as a dither tuning fork, while the other is used as a measuring tuning fork. An electrically conductive Pt90Ir10 tip enables the sensor to work in both scanning tunneling microscopy (STM) and AFM modes. Electronic circuits for self-oscillation control and for frequency detection are given in detail. Atomically resolved STM and ncAFM images of a thin alumina film on NiAl(110) are shown with the microscope cooled down to 4.5 K by liquid helium. (c) 2006 American Institute of Physics.