Potential sensitivities in frequency modulation and heterodyne amplitude modulation Kelvin probe force microscopes

Abstract

In this paper, the potential sensitivity in Kelvin probe force microscopy (KPFM) was investigated in frequency modulation (FM) and heterodyne amplitude modulation (AM) modes. We showed theoretically that the minimum detectable contact potential difference (CPD) in FM-KPFM is higher than in heterodyne AM-KPFM. We experimentally confirmed that the signal-to-noise ratio in FM-KPFM is lower than that in heterodyne AM-KPFM, which is due to the higher minimum detectable CPD dependence in FM-KPFM. We also compared the corrugations in the local contact potential difference on the surface of Ge (001), which shows atomic resolution in heterodyne AM-KPFM. In contrast, atomic resolution cannot be obtained in FM-KPFM under the same experimental conditions. The higher potential resolution in heterodyne AM-KPFM was attributed to the lower crosstalk and higher potential sensitivity between topographic and potential measurements.

Quantitative analysis of sideband coupling in photoinduced force microscopy

“…Eqs. (4) and 5are the general expressions of our sideband coupling theory in multifrequency atomic force microscopy. If the form of F (t) is known, the amplitudes A 1 , A mi , A si± and the phase shifts θ 1 , θ mi , θ si± can be calculated through numerical integration.…”

“…The principle of multifrequency AFM is based on the notion that multiple frequency channels can be used simultaneously, opening up the possibility to examine different tip-sample interactions at the same time 2 . 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] .…”

Fast, high-resolution surface potential measurements in air with heterodyne Kelvin probe force microscopy

“…A recent technique, Heterodyne (H) KPFM, operates similarly to FM-KFPM but separates the topography and voltage signals by hundreds of kHz [39]. Originally, in vacuum, the separation was utilized to increase the voltage sensitivity through amplification by the second cantilever eigenmode, while maintaining spatial resolution equal to FM-KPFM [39,41]. Measurements in vacuum show that H-KPFM, like FM-KPFM, avoids the stray capacitance artifact that affects AM-KPFM [15].…”

“…In H-KPFM, both the detection frequency, f D and the carrier oscillation frequency, f CA , are free to be chosen, and once chosen, determine the frequency at which V AC is applied, f A . Earlier works on H-KPFM considered the case f CA = f 1 , the first cantilever resonance, and f D = f 2 , the second cantilever resonance[15,39,41]. In this article, this implementation is called "H2" for heterodyne amplified by the second cantilever resonance.…”

Atomic species recognition on oxide surfaces using low temperature scanning probe microscopy

“…Consequently, KPFM or STM experiments can be performed simultaneously to completely separate the potential or electrical density information from the topography. [37][38][39]…”