Description of the publication:


Sikora, A., Bednarz, £.


The implementation and the performance analysis of the multi–channel software–based lock–in amplifier for the stiffness mapping with atomic force microscope (AFM)


Bulletin of the Polish Academy of Sciences: Technical Sciences




60 (1)









atomic force microscopy; lock–in amplifier; software development; stiffness mapping; torsional oscilators


In this paper the implementation of the surface stiffness mapping method with the dynamic measurement mode of atomic force microscopy (AFM) is presented. As the measurement of the higher harmonics of the cantilever's torsional bending signal is performed, we are able to visualize non–homogeneities of the surface stiffness. In order to provide signal processing with the desired sensitivity and selectivity, the lock–in amplifier–based solution is necessary. Due to the presence of several useful frequencies in the signal, the utilization of several simultaneously processing channels is required. Therefore the eight–channel software–based device was implemented. As the developed solution must be synchronized with the AFM controller during the scanning procedure, the real–time processing regime of the software is essential. We present the results of mapping the surface stiffness and the performance tests results for different working conditions of the developed setup.


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Example figure:

The PXI unit performance chart for various operation conditions.

Used methods:

Phase Imaging