Bi-harmonic cantilever design for improved measurement sensitivity in tapping-mode atomic force microscopy
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- Muthukumaran Loganathan
- Missouri University of Science and Technology Department of Mechanical and Aerospace Engineering, , Rolla, Missouri 65401, USA
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- Douglas A. Bristow
- Missouri University of Science and Technology Department of Mechanical and Aerospace Engineering, , Rolla, Missouri 65401, USA
説明
<jats:p>This paper presents a method and cantilever design for improving the mechanical measurement sensitivity in the atomic force microscopy (AFM) tapping mode. The method uses two harmonics in the drive signal to generate a bi-harmonic tapping trajectory. Mathematical analysis demonstrates that the wide-valley bi-harmonic tapping trajectory is as much as 70% more sensitive to changes in the sample topography than the standard single-harmonic trajectory typically used. Although standard AFM cantilevers can be driven in the bi-harmonic tapping trajectory, they require large forcing at the second harmonic. A design is presented for a bi-harmonic cantilever that has a second resonant mode at twice its first resonant mode, thereby capable of generating bi-harmonic trajectories with small forcing signals. Bi-harmonic cantilevers are fabricated by milling a small cantilever on the interior of a standard cantilever probe using a focused ion beam. Bi-harmonic drive signals are derived for standard cantilevers and bi-harmonic cantilevers. Experimental results demonstrate better than 30% improvement in measurement sensitivity using the bi-harmonic cantilever. Images obtained through bi-harmonic tapping exhibit improved sharpness and surface tracking, especially at high scan speeds and low force fields.</jats:p>
収録刊行物
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- Review of Scientific Instruments
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Review of Scientific Instruments 85 (4), 2014-04-01
AIP Publishing