2008 NSTI Nanotechnology Conference and Trade Show - Nanotech 2008 - 11th Annual

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Clean Technology 2008

Quantitative non-contact lateral force gradient and dissipation measurement using small oscillation amplitude lateral force combined with tunneling microscopy

M. Atabak, Ö. Unverdi, S. Özer, H.Ö. Özer, A. Oral
Kanazawa University, JP

Keywords:
lateral force, small amplitude, Atomic force microscopy

Abstract:
Lateral force microscopy has shown its capability to manipulate single atom and molecules laterally, however quantitative measurement of lateral forces that govern the activated or induced movement of atomic or molecular scale objects along surface has still remained a challenge. To investigate this important issue, we specially designed and constructed a nc-AFM, capable of measuring lateral stiffness simultaneously with tunneling current. In our technique a sensitive fiber interferometer is aligned at the side of a home–made tungsten cantilever with typical stiffness of about 100 N/m. To improve the sensitivity, a RF circuit is designed to inject RF current into the laser diode. The frequency and the amplitude of the RF current can be adjusted to optimize the noise reduction. Using this technique a noise level of ~910-5 Å/ is obtained. The cantilever is dithered in lateral direction respect to the sample with sub-Ångstrom oscillation amplitudes (A0 =0.25 Å) at a frequency, well below the resonance frequency and the changes in lateral oscillation amplitudes. The amplitude at the tip, which is altered by the tip-surface, is detected from the interferometer output using a lock-in amplifier. We present lateral stiffness and tunnel topography images on Si(111)- (77) surface as well as the direct measurement of lateral force and interaction energy due to lateral tip-sample interaction at the varying tip- sample separation.


Nanotech 2008 Conference Program Abstract