Application of the method of synchronous detection for higher-harmonics imaging in tapping-mode atomic force microscopy

摘要: Abstract In tapping-mode atomic force microscopy (AFM), the interaction between tip and sample is in fact non-linear consequently higher harmonics of fundamental resonance frequency oscillating cantilever are generated. this paper, we present an AFM system with a novel approach to higher-harmonics imaging. The uses method synchronous detection, based on Fourier method, which allows record simultaneously amplitudes phases harmonics. used detection system, composed 16-bit 100 mega-samples per second (MSPS) analog-to-digital converter (ADC) field-programmable gate array (FPGA) device, measure amplitude phase within one oscillation cycle good signal-to-noise ratio. As result, good-quality images at could be obtained use conventional cantilevers. results prove that imaging can distinguish different materials.