Sideband Kelvin Probe Force Microscopy
KPFM signal sensitivity and the cantilever spring constant, and that a lower spring constant of the cantilever yields higher sensitivity than stiffer cantilevers. Further study is necessary to understand the correlation between KPFM signal sensitivity and cantilever length.
References [1] Park Systems Application Technology Center, A Comparative Study of Atomic Force Microscopy between AM KPFM and Sideband KPFM, Principles and Applications,
https://parksystems.com/images/media/appnote/ AppNote-61_sideband-KPFM_A-comparative-study.pdf.
[2] H Seo et al., How to obtain sample potential data for KPFM measurement.
https://parksystems.com/images/ media/appnote/How-to-obtain-sample-potential-data- for-KPFM-measurement-18.pdf.
[3] A Cerreta et al., Exploring the Potential of the Sideband KPFM Mode. Park Systems Webinar, https://
parksystems.com/medias/nano-academy/webinars/115- webinars/1850-exploring-the-potential-of-the-sideband- kpfm-mode-april-9-2020.
[4] T Fukuma et al., Rev Sci Instr 76 (2005) https://doi. org/10.1063/1.1896938.
Figure 6: Surface potential difference of F14 H20 via sideband KPFM: (a) surface
potential imaged with probe NSC14/Cr-Au; (b) surface potential imaged with probe NSC36C/Cr-Au; (c) line profiles taken along red line in (a) and green line in (b).
of resolution when using the sideband mode relies on the local interaction between the tip apex and sample. Te topography images indicate that the F14
H20 aggregates of this sample form
an incomplete spiral superstructure (Figure 5). Tese incomplete spirals tend to form more compacted superstructures, reducing the in-between spaces of the aggregates [5]. Figure 6 shows the results of the correlation between the
spring constant of the cantilever and KPFM signal-to-noise ratio sensitivity. Cantilever NSC14/Cr-Au (Figure 6a) shows a lower sensitivity for the surface potential changes than cantilever NSC36-C/Cr-Au (Figure 6b). Line profiles taken from images shown in Figures 6a and 6b demonstrate that using either type of cantilever tip allows sideband KPFM to detect small changes in the surface potential, even between the F14
H20 superstructures.
Te fact that NSC36-C/Cr-Au shows a higher KPFM signal sensitivity, and has a spring constant that is almost ten times smaller than NSC14/Cr-Au, indicates a correlation between the spring constant of the probe and the sensitivity. Equation 4 establishes that the length of the cantilever is also crucial for EFM amplitude sensitivity; both cantilevers have almost the same length, so the correlation between cantilever length and EFM sensitivity is not analyzed. Further experiments are needed to investigate the correlation between the cantilever’s length, the EFM amplitude, and the KPFM signal sensitivity.
Summary In this study, sideband KPFM on a Park NX10 atomic force microscope was used to image F14
H20 molecular structures. Tis
study validates sideband KPFM as a technique that measures the surface potential with higher sensitivity and spatial resolution when compared to the conventional off-resonance KPFM techniques. Te results suggest a correlation between
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[5] A Mourran et al., Langmuir 21 (2005) https://doi. org/10.1021/la048069y.
[6] Atomic Force Microscopy View on Structural Organization of Semifluorinated Alkanes, F14
H20 , SPM Labs LLC, http://
nebula.wsimg.com/31925a3276fc02b2bdf258d8aa7638 76?AccessKeyId=3A83BC9B73732C557ED0&disposit ion=0&alloworigin=1.
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