Aqueous Solution Structure over α-Al2O3(01(1)over-bar2) Probed by Frequency-Modulation Atomic Force Microscopy

An alpha-Al2O3(01 (1) over bar2) wafer was immersed in an aqueous KCl solution of 1 mol L-1 and observed with a frequency-modulation atomic force microscope. The tip-surface force was precisely determined as a function of the tip-surface distance. The force-distance relationship contained oscillations accompanied with an exponentially decayed, electric double layer force. The force oscillations were ascribed to liquid water layers confined over the Al2O3 surface.