EFFECT OF PROBE FORCE ON THE RESOLUTION OF ATOMIC-FORCE MICROSCOPY OFDNA

Experimental results are presented to show that the adhesion force is the single most important limiting factor in high-resolution atomic fo rce microscopy of DNA in air, prepared by the cytochrome-C-assisted sp reading method. It is also shown that humidity plays a minor role in t he control of probe force. Using a pure carbon film as the substrate t o clean the AFM tip prior to imaging, it is demonstrated that 4-6 nm r esolution on DNA can be routinely obtained by the atomic force microsc ope with commercial Si3N4 pyramid cantilevers. We also show that in or ganic solvents a resolution of up to 3 nm can be obtained under optima l conditions.