Recently, chemical force microscopy (CFM)  is used as a tool for chemical discrimination of surface chemical species. For CFM, friction force microscopy (FFM) , phase-lag imaging in tapping mode atomic force microscopy (TM-AFM) , and adhesive force mapping by pulsed-force-mode AFM (PFM-AFM)  have been used to discriminate various terminal groups of self-assembled monolayers (SAMs) using the AFM tips covered with SAMs of thiols or organosilanes terminating in a variety of functional groups [5,6].
In the present papers, we will describe the recent experimental results of CFMs of patterned surfaces with SAMs prepared by microcontact printing and deposition of phase-separated monolayers with the Langmuir-Blodgett (LB) method. Both surfaces was observed by FFM and PFM-AFM for CFM. We will also discuss the difference in contrast mechanisms of FFM and PFM-AFM based upon the molecular dynamic simulation and the simple phenomenological simulation [7-9].
For CFM, chemical modification of AFM tips plays a crucial role. As described above, silanization of oxide tip surfaces and SAM formation of gold coated AFM tips with thiol or sulfide have been used as the chemical modification methods. For the latter method, a new two-step precleaning procedure of gold coated surface was also studied in this laboratory . The two-step cleaning procedure involves i) oxidation of organic contaminants on the AFM tips with ozone treatment and ii) reduction of the oxidized gold surface by immersing the oxidized tip into pure hot ethanol. The chemically modified tips prepared from gold coated AFM tips precleaned by the two-step procedure gave almost the same tip characteristics as those chemically modified immediately after gold vapor deposition in a factory. We will describe that the present two-step cleaning procedure can be used widely for chemical modification of commercially available gold coated AFM tips with thiol or disulfide compounds for CFM.
We will also describe a new method of CFM for single molecular detection.
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Professor Masamichi Fujihira
Department of Biomolecular Engineering, Tokyo Institute of Technology
4259 Nagatsuta, Midori-ku, Yokohama 226, JAPAN
Tel: +81 45 924 5784; FAX: Int. +81 45 924 5817