Thermal Noise Response Based Static Non-Contact Atomic Force Microscopy
A. Gannepalli, A. Sebastian, M.V. Salapaka and J. Cleveland
Iowa State University, US
Keywords: thermal noise response, cantilever resonance, non-contact force microscopy, static mode operation, tip-sample separation control
Micro-cantilever based devices have revolutionized imaging and they are the primary tools for investigation and control of matter at the nanoscale. In this paper a novel approach based on the thermal noise response of the cantilever is developed that makes non-contact AFM possible in static mode. This technique exploits the dependence of cantilever's resonant frequency on the tip-sample separation to maintain a small tip-sample separation by regulating the equivalent resonant frequency. The resonant frequency is estimated from cantilever's response to the thermal noise. The experiments performed in ambient room conditions have achieved tip-sample separations as small as 4 nm for time periods in excess of 20 min. Based on this control technique a new static non-contact mode operation of AFM has been demonstrated. This method has given rise to an extremely powerful non-contact imaging technique capable of detecting sub-angstorm features at a bandwidth of 200 Hz with a force sensitivity of a few pN.
Nanotech 2004 Conference Technical Program Abstract