A review of atomic force microscopy imaging systems: application to molecular metrology and biological sciences

The atomic force microscope (AFM) system has evolved into a useful tool for direct measurements of micro-structural parameters and unraveling the intermolecular forces at nanoscale level with atomic-resolution characterization. Typically, these micro-cantilever systems are operated in three open-loop modes; non-contact mode, contact mode, and tapping mode. In order to probe electric, magnetic, and/or atomic forces of a selected sample, the non-contact mode is utilized by moving the cantilever slightly away from the sample surface and oscillating the cantilever at or near its natural resonance frequency. Alternatively, the contact mode acquires sample attributes by monitoring interaction forces while the cantilever tip remains in contact with the target sample. The tapping mode of operation combines qualities of both the contact and non-contact modes by gleaning sample data and oscillating the cantilever tip at or near its natural resonance frequency while allowing the cantilever tip to impact the target sample for a minimal amount of time. Recent research on AFM systems has focused on many manufacturing and metrology processes at molecular levels due to its tremendous surface microscopic capabilities. This paper provides a review of such recent developments in AFM imaging system with emphasis on operational modes, micro-cantilever dynamic modeling and control. Due to the important contributions of AFM systems to metrology and biological sciences, this study also provides a comprehensive review of recent applications of different AFM systems in these two important areas. (C) 2004 Elsevier Ltd. All rights reserved.