Applying Second and Third Resonance Frequencies to Surface Potential Measurements with Kelvin Probe Force Microscopy

Abstract

Frequency separation between topography and potential scans in Kelvin probe force microscopy (KPFM) was investigated. Topographic images were scanned via the first resonance frequency of the cantilever excited mechanically. Potential images were scanned via the first, second, or third resonance frequency of the cantilever excited electrostatically. Good separation of the mechanical modulation to the cantilever in AC mode and the potential modulation to the probe tip was obtained when the second or third modulation frequency was used. Higher resonance modes led to a decreased capacitive effect between the cantilever and sample, which resulted in better lateral resolution of potential measurements, mainly owing to the tip-sample capacitive effect. The shorter time scale of amplitude change in the cantilever oscillation for the higher resonance frequencies led to wellconverged potential measurements. The second and third resonance frequencies are useful for separating signals in KPFM, resulting in better lateral resolution and potential difference measurements of the sample surface.

Comparing the performance of single and multifrequency Kelvin probe force microscopy techniques in air and water

“…(5) We consider the capacitive terms to be equivalent for different eigenmodes, allowing for a direct division of the electrostatic force harmonics in order to access CPD. Some authors have indicated that the capacitance contribution of the lever differs at higher eigenmodes due to the mode shape of the cantilever [17,60,63]. This would primarily affect the accuracy of CPD for purely electrical modes dependent on C′ as the mechanically coupled modes dependent on C″ have minimal cantilever contribution [101].…”

“…Higher eigenmodes typically have poorer SNRs than the fundamental eigenmode since k n increases more rapidly than Q n [60,61]. However, these modes still offer significant SNR enhancements over off-resonance techniques, higher spatial resolution due to reduced influence of the cantilever to the electrostatic forces [17,60,63], and higher bandwidth than side-band techniques [10,58]. All modes of KPFM can in principle be applied in any of these scenarios.…”

Two‐step hydrothermal fabrication of Na 0.23 TiO 2 nanofibers and enhanced photocatalysis after loaded with gold or silver determined by surface potentials

“…Scanning Kelvin probe microscopy (SKPM) measures the contact potential difference between the sample and probe tip, corresponding to the work function. Recently, SKPM was used to characterize the work function of metallic samples and the surface potential of semiconductor samples . In this paper, the surface potential of NTO loaded with Au was measured by an SPM equipped with SKPM to determine the charge distribution under light illumination with different wavelengths and then to reveal the photocatalytic mechanism.…”