Phase contrast and operation regimes in multifrequency atomic force microscopy

Abstract

In amplitude modulation atomic force microscopy the attractive and the repulsive force regimes induce phase shifts above and below 90°, respectively. In the more recent multifrequency approach, however, multiple operation regimes have been reported and the theory should be revisited. Here, a theory of phase contrast in multifrequency atomic force microscopy is developed and discussed in terms of energy transfer between modes, energy dissipation and the kinetic energy and energy transfer associated with externally driven harmonics. The single frequency virial that controls the phase shift might undergo transitions in sign while the average force (modal virial) remains positive (negative). © 2014 AIP Publishing LLC.Peer ReviewedPostprint (published version

Periodicity in bimodal atomic force microscopy

“…Finally, the energy irreversibly lost to the tip-sample interaction E dis is the contribution of energy transfer from all modes, 7,37 i.e., in bimodal, the first two modes, as…”

“…Mode numbers are bracketed in this work to distinguish them from harmonic number n as done elsewhere. 23,37 The external drive frequencies are x D1 and x D2 ; D1 and D2 stand for drives 1 and 2, respectively. Typically, x D1 % x (1) and x D2 % x (2) .…”

Interfacial interaction and enhanced image contrasts in higher mode and bimodal mode atomic force microscopy

“…For the complex nonlinear interaction system of the tip-sample, dissipated power and virial have been employed to plot the relative dominance of conservative and non-conservation (dissipative) interfacial interactions. [17][18][19] Energy transfer or change between two modes may determine the origin of the contrast. 20 Phase contrast is closely connected to the magnitude of the dynamic dissipated power per vibrating cycle during the cantilever scanning on the surface by AM-AFM mode.…”

Optimization of phase contrast in bimodal amplitude modulation AFM

“…A transition between the regimes is usually accompanied by a sudden change of the observables (amplitude and phase shift). In bimodal AFM some additional contrast regimes has been identified [35–37] where sudden changes of the phase contrast are not associated with changes in the sign of the average value of the force. The origin of those regimes are discussed in terms of the different energies of the system, kinetic energy of the exited modes [35–38], the input energy [36] or the energy transfer between the modes [37].…”