FABRICATION OF A NEW SUBSTRATE FOR ATOMIC-FORCE MICROSCOPIC OBSERVATION OF DNA-MOLECULES FROM AN ULTRASMOOTH SAPPHIRE PLATE

A new stable substrate applicable to the observation of DNA molecules by atomic force microscopy (AFM) was fabricated from a ultrasmooth sap phire (alpha-Al2O3 single crystal) plate, The atomically ultrasmooth s apphire as obtained by high-temperature annealing has hydrophobic surf aces and could not be used for the AFM observation of DNA. However, sa pphire treated with Na3PO4 aqueous solution exhibited a hydrophilic ch aracter while maintaining a smooth surface structure. The surface of t he wet-treated sapphire was found by x-ray photoelectron spectroscopy and AFM to be similar to 0.3 nm. The hydrophilic surface character of the ultrasmooth sapphire plate made it easy for DNA molecules to adher e to the plate. Circular molecules of the plasmid DNA could be imaged by AFM on the hydrophilic ultrasmooth sapphire plate.