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Appl. Sci. 2017, 7(7), 704;

Creation of Optimal Frequency for Electrostatic Force Microscopy Using Direct Digital Synthesizer

Division of Industrial Metrology, Korea Research Institute of Standards and Science, Daejeon 34113, Korea
Department of Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Korea
Mass Spectrometry & Advanced Instrumentation Group, Korea Basic Science Institute, Cheongju 28119, Korea
Nuclear Fusion & Plasma Laboratory, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
Author to whom correspondence should be addressed.
Academic Editor: Giorgio Biasiol
Received: 19 May 2017 / Revised: 29 June 2017 / Accepted: 5 July 2017 / Published: 8 July 2017
(This article belongs to the Section Materials)
View Full-Text   |   Download PDF [2346 KB, uploaded 8 July 2017]   |  


Electrostatic force microscopy (EFM) is a useful technique when measuring the surface electric potential of a substrate regardless of its topography. Here, we have developed a frequency detection method for alternating current (AC) bias in EFM. Instead of an internal lock-in amplifier (LIA) for EFM that only detects ωe and e, we have used other LIAs that can amplify the amplitude of specific frequency by direct digital synthesizer (DDS), that finds the optimal frequency of surface charge images. In order to confirm the performance of the proposed methods, the electrical properties of lead zirconate titanate (PZT) and triglycine sulfate (TGS) samples were measured. In addition, we compared the performances of the frequency-detection method and the conventional EFM method. Ultimately, enhanced images could be achieved using the frequency-detection method. The optimal modulated frequency-shift for force–gradient measurements was found to be 2 kHz. Additionally, we have shown that it is possible to use a hard cantilever (K = 42 N/m, 330 kHz). Therefore, we expect that this technique can be applied to measure the electrical properties of bio-molecular films. View Full-Text
Keywords: electrostatic force microscopy; EFM; direct digital synthesizer; PZT; TGS electrostatic force microscopy; EFM; direct digital synthesizer; PZT; TGS

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Moon, S.; Kang, M.; Kim, J.-H.; Park, K.-R.; Shin, C. Creation of Optimal Frequency for Electrostatic Force Microscopy Using Direct Digital Synthesizer. Appl. Sci. 2017, 7, 704.

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