Research Of The Atomic Force Microscope System Based On Tuning Fork Probe

As an important measurement technology,the atomic force microscope(AFM)is able to conduct dimensional measurement for structural surfaces with a nanometer resolution.It has wide application prospect in nanofabrication,detection of the sample topography and nano-metrology.In this paper,atomic force microscope system based on tuning fork probe is taken as the research object,and the following aspects are studied:The vibration characteristics of tuning fork probe are studied theoretically.Based on the simplified mechanical model of three springs and two particles,the oscillation form of the probe's tuning fork are determined by modal analysis and harmonic response analysis;The interaction force between probe tip and sample was calculated by atomic force model and Derjaguin-Muler-Toporov(DMT)model and the response characteristics of the probe's amplitude are simulated by dynamic equations during the process of probe tip approaching sample.A small self-induction tuning fork gauge head is designed.The probe of gauge head consists of quartz tuning fork and chemically ground tungsten wire.The resonance frequency is above 25 kHz and the quality factor is over 1000;The circuit module of the gauge head is developed to realize the vibration excitation of the probe as well as 10~8 times magnification of probe's output signal and compensation of parasitic capacitance.An experimental device of atomic force microscope system based on tuning fork probe was built.The device mainly includes signal extraction module,multi-motion platform control system and micro-observation module.In the signal extraction module,the amplitude information of the probe's signal are obtained by using a phase-locked amplifier;The multi-motion platform control system is used to realize the movement of probe and sample.Microscopic observation module is used to collect image during the approaching process of probe tip and sample;The control software of device based on C++is compiled to realize the control of multiple devices and the output of testing results.The noise characteristics of the tuning fork gauge head and the force-displacement curve of the probe tip approaching the sample surface under amplitude modulation mode were measured experimentally.The experimental results show that the vertical resolution of the device is less than 0.1 nm;Through this device,the scanning measurement experiments of step and grid samples were carried out,and the surface micro-topography of the samples was obtained.The experimental results show that the device can be effectively applied to the surface measurement of nano-scale samples.