Ultrafast pump-probe force microscopy with nanoscale resolution

Abstract

We perform time-resolved pump-probe microscopy measurements by recording the local force between a sharp tip and the photo-excited sample as a readout mechanism for the material's nonlinear polarization. We show that the photo-induced force is sensitive to the same excited state dynamics as measured in an optical pump-probe experiment. Ultrafast pump-probe force microscopy constitutes a non-optical detection technique with nanoscale resolution that pushes pump-probe sensitivities close to the realm of single molecule studies.

Nanoscale chemical imaging by photoinduced force microscopy

“…The technique, now called photoinduced force microscopy (PiFM), can measure both linear ( 23 ) and nonlinear ( 24 ) sample polarizability by detecting the force gradient between the interaction of the optically driven molecular dipole and its mirror image dipole in a metal-coated AFM tip. This near-field excitation and near-field detection (as opposed to near-field excitation and far-field detection in other tip-enhanced near-field optical microscopy techniques described earlier) allow the detection of near-field optical response with no far-field background contribution ( 23 – 26 ). The use of dynamic AFM (also known as tapping mode or noncontact AFM) provides good sensitivity due to the high quality factor ( Q ~ 600) of the cantilever and minimal tip-sample interaction, making it ideal for soft matter such as BCPs.…”

The limit of time resolution in frequency modulation atomic force microscopy by a pump-probe approach

“…In addition, small perturbations of the tunnel gap as a result of synchronous thermal expansion is a cause of potential artifacts. Fast time resolution in AFM was achieved in 2015 by Jahng et al to measure the dynamics in silicon naphtalocyganine using a technique named photo induced force microscopy (PIFM) [25]. PIFM measures the force generated by the light induced dipoles in the tip and sample.…”

Quantitative analysis of sideband coupling in photoinduced force microscopy

“…By detecting the amplitude and phase of multiple eigenmodes, the experiment can be optimized to detect, for instance, local variations in the contact difference potential [3][4][5] along with local mechanical measurements of material stiffness and damping 6,7 . Another example is photo-induced force microscopy (PiFM), which uses one cantilever eigenmode for registering sample topography and a second mechanical eigenmode for detecting photoinduced forces in the tip-sample junction [8][9][10][11][12][13][14][15][16] .…”