During my readings ( in many article) mainly focused in Kelvin Probe Force Microscopy(KPFM), I have remarked that the autors apply an external ac voltage for determing the contact potential between the probe and the sample . I would like then to know why piezoelectric tube does not allows us to do this measurement.
Thank you very in advance
Dear Christian
In KPFM technique, the cantilever is not piezoelectrically driven at its mechanical resonance frequency as in normal AFM . Although an AC voltage is applied at this frequency.
The reason that we use AC voltage to oscillate the cantilever instead of piezoelectric crystal is that the applied ac bias at frequency ω is causing the electric force to modulate at both ω and 2ω. Oscillation amplitude at ω drops to 0
when V(DC)=V(CPD) (contact potential difference), which is the idea of nulling electric force to find surface potential in amplitude modulation KPFM.
For more information, I would recommend reading the application note for KPFM from Bruker.
Hope this helps you in your research.
Good luck!
of course! Dear Reza, your contributions were very useful. I believe that i I got the point. thank very much.
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