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Measuring surface potential with KFM

Posted: 26 Dec 2012 ?? ?Print Version ?Bookmark and Share

Keywords:kelvin force microscopy? surface potential? multi-frequency technique?

Scanning kelvin force microscopy (KFM) has been widely employed in mapping surface potential (SP) distribution at the nanoscale. There are two different approaches in KFM imaging, i.e., Lift Mode and Single-Pass. In Lift Mode, topography and SP images are acquired in two different scans: the topography is obtained first and the tip then lifted to a certain distance above the topography for a second scan to measure SP. In Single-Pass, topography and SP are acquired simultaneously using a multi-frequency technique: the cantilever is excited simultaneously with two ac modulation signals at different frequencies, the first one is used for mechanical excitation to measure topography and the second one, usually with a much lower frequency, is for electric modulation to measure SP. Single-Pass KFM is implemented in Agilent's AFM systems using a high performance triple lock-in AC Mode controller. Detailed instrumentation and discussion of Single-Pass KFM techniques can be found in other Agilent application notes. KFM contrast reveals important information about surface charging, molecular dipole orientation in organic thin fi lms, band bending and dopant concentration in semiconductor materials, etc. There are also reports that use KFM to measure the work function of a conducting material, e.g., the change in work function with fi lm thickness of few-layer graphene. However, the reported values measured by KFM are not always consistent in literature. This note will discuss a number of experimental parameters that have significant effect on the accuracy and resolution of SP measurements.

View the PDF document for more information.

Originally published by Agilent Technologies at as "Quantitative Surface Potential Measurement Using KFM: Effects of Imaging Parameters and Experimental Conditions".

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