Physical interpretation of measurements
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How should X(real) and Y(imaginary) components of the PFM measurement be interpreted? I know in mechanical measurements they're the pure elastic and viscous responses, respectively, but I don't know the analogous electromechanical properties in PFM.
Also, which data are more meaningful to report: X or R?
Thanks! -
Strictly speaking, signal flow in PFM is:
excitation signal (khown amplitude and phase) -> electronic circuit (for low frequencies just resisto, but above 1 MHz RLC things can be important) -> electromechnical contact (materials response) -> cantilever transfer function -> detection electronics.
Practically, you measure product of all these transfer functions, and osme of them are not separable (eigenresponses of cantilever depend on contact). So, dissipation 9Q factors) can be measure dreliably, but frequency dispersion of signal is very unlikely.
As an example, Kathy Wahl reported (JAP or RSI 2001?) a very nice calibration work for nanoindentor, but it was already tough, and nanoindentation is generally much more quantitative then SPM -
Sergei,
Piezoelectric loss factor originating mostly from the macroscopic domain wall motion is around 5-10\%. Can we say something about the single domain loss by measuring the PFM phase when the tip is located near the domain wall. Or it is indistinguishable from other sources of phase distortion? -
Good question. You can do it by measuring band-excitation SS-PFM near domain wall. Good idea.
10\% may actually be measurable. -
whell, the low-frequency value and r_res/Q are only weakly loss-dependent, as in any SHO