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PeakForce Tapping Technology Creates New Possibilities in KPFM

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Bruker Posted: Wed, Nov 14 2012 5:39 PM

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Bruker's Exclusive PeakForce Tapping Technology
Creates New Possibilities in KPFM

November 2012


PeakForce Tapping Reaches 100 Citations
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PeakForce Technology Creates New Possibilities in KPFM

Bruker is dedicated to advancing atomic force microscopy technologies and is leading innovation in both conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM), which is also known as surface potential microscopy. KPFM maps electrostatic potential at sample surfaces to provide information about electronic structure, doping level variations, trapped charges, and chemical identity in applications ranging from organic photovoltaics research to silicon and wide bandgap semiconductor characterization.

PFT LiBattery
Topography (left) and PeakForce KPFM workfunction (right) of carbon nanotube bundle. Detecting workfunction difference for 2nm wide nanotube, quantitative workfunction measurement for
30nm wide bundle.
Bruker's proprietary PeakForce Tapping™ has revolutionized the industry, delivering new possibilities and advancing science in countless ways. Our exclusive PeakForce TUNA™ has also broken barriers to advance CAFM by enabling conductivity imaging where it was impossible before, and by maintaining highest spatial resolution on the most fragile samples through the elimination of lateral forces. Likewise it provides correlated nanomechanical information. Now, this technology has been further utilized to advance the possibilities of KPFM.

Past Limitations

In principle, KPFM can provide a quantitative measure of the work function difference between sample surfaces and AFM tips. In practice, when interrogating relevant samples (i.e., nanoscale structures with variations in modulus or adhesion), conventional ambient, TappingMode-based KPFM approaches face severe limitations. This is true for both the commonly used detection mechanisms of amplitude modulation (AM) and frequency modulation (FM). Where AM detection suffers from a lack of spatial resolution due to the whole cantilever's contribution to the error signal, FM is subject to mechanical cross-talk and lack of sensitivity. This mechanical cross-talk originates from the fact that nanomechanical tip-sample interactions shift the cantilever resonance behavior and thus affect sideband detection employed in FM. Sensitivity limitations stem from the need for high-k (for stable oscillation), low-Q (for tapping response bandwidth) cantilevers for TappingMode, the exact opposite of what maximizes KPFM sensitivity. Furthermore, parameter set up complexity in conventional KPFM can limit user-to-user consistency.

Height, PeakForce KPFM potential, and PeakForce QNM adhesion measurement
of Sn-Pb alloy. Quantitative workfunction measurement directly correlated with nanomechanical map. Image size 4 microns.
PeakForce KPFM takes full advantage of the high spatial resolution afforded by FM KPFM while avoiding its pitfalls. By employing Bruker's patented LiftMode™, it avoids mechanical crosstalk. By building on the suite of PeakForce Tapping technology, it aligns cantilever needs, providing highest resolution topography with the same low-k, high-Q cantilevers, maximizing potential sensitivity. In these ways, PeakForce KPFM can resolve and quantify nanoscale work function variations that are extremely challenging for TappingMode. In addition, PeakForce QNM® provides directly correlated quantitative nanomechanical information. The new PeakForce KPFM mode offers consistent and quantitative work function measurements at the highest spatial resolution. Aside from its signature mode, the PeakForce KPFM package also includes all industry standard KPFM implementations, as well as a high-voltage mode, extending the usually accessible potential range by more than a factor of 10. Across the board, automatic setup with ScanAsyst® guarantees consistently optimized results even for the non-expert AFM user. Whether imaging potential variations in complex materials, interrogating electronic structure in semiconductor samples or utilizing work function variations to map chemical distributions, the unparalleled capabilities of PeakForce KPFM for Dimension Icon® and MultiMode® 8 AFMs will allow you to measure more accurately and learn much more about your samples.

Find out more about Bruker's advanced PeakForce KPFM by visiting the website,or download the datasheet HERE.
© 2012 Bruker Corporation. All rights reserved.

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