Measuring Electric Field Induced Subpicometer Displacement of Step Edge Ions

Abstract

We provide unambiguous evidence that the applied electrostatic field displaces step atoms of ionic crystal surfaces by subpicometers in different directions via the measurement of the lateral force interactions by bimodal dynamic force microscopy combined with multiscale theoretical simulations. Such a small imbalance in the electrostatic interaction of the shifted anion-cation ions leads to an extraordinary long-range feature potential variation and is now detectable with the extreme sensitivity of the bimodal detection.

Energy Loss Triggered by Atomic-Scale Lateral Force

“…Figure 1 shows simultaneous measurements of the frequency shifts Áf and the energy dissipation E for both modes, measured at quasiconstant height: The measured topographic contrast is as small as 1 pm, thus below the sensitivity of the digital electronics. The Áf Z , Áf TR , and E Z maps reveal the well-known atomic pattern of NaCl (001): As a result of the large flexural amplitude, the Áf Z contrast is weak and noisy, while the Áf TR signal, affected only by lateral site-dependent interactions [44], gives very high resolution [42,43]. The overall magnitude of the energy dissipation in the flexural mode E Z is quite large (% 4:5 eV), and it systematically increases as the tip-sample distance is reduced (see Fig.…”

“…The DFM experiments were performed with our homemade ultrahigh vacuum apparatus, operating at room temperature [41]; the tip was indented into the sample prior the measurements. Vertical and lateral tip-sample interactions were measured by using bimodal DFM from the flexural and torsional resonance frequency shifts of a commercially available Si cantilever [42][43][44]. The frequency shifts of both flexural Áf Z and torsional modes Áf TR were detected with two sets of the digital phase-locked loop (Nanonis: dual-OC4), and the amplitudes (A Z and A TR ) were kept constant by controlling the excitation signals to the dither piezoelectric actuator; from the excitation signals, the vertical E Z and lateral E TR energy dissipations were obtained [45].…”

Fast nanomechanical spectroscopy of soft matter

“…In the recent years, several methods have been proposed to complement the high spatial resolution of the force microscope with quantitative information about the mechanical properties of the interface [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] . In fact, the goal of combining topography with compositional contrast can be traced back to the origin of dynamic AFM with the development of phase-imaging AFM.…”

Flexible and modular virtual scanning probe microscope

“…The advantage to using these virtual machines is that they are designed to capture all aspects of a typical AFM experiment, including instrument induced artefacts. Without a complete simulation of the experimental setup, it is often impossible to directly compare theoretical predictions with experimental images in more complex techniques [22][23][24][25], particularly where analytical solutions are not available to describe the modes of operation. Generally, the available implementations only describe one particular experimental setup, usually operating in frequency modulation, and were developed specifically for an expert scientific user.…”