AFM Study of Water Meniscus Formation between an AFM Tip and NaCl Substrate

Water meniscus formation at the point of contact between an AFM tip and an atomically smooth NaCl substrate was experimentally studied as a function of atmospheric water content, from 70% relative humidity to ultrahigh vacuum (UHV). Meniscus formation was probed by measuring the pull-off point and evaluating the ability of the meniscus to dissolve the NaCl near the point-of-contact as a function of atmospheric water content. Hydrophilic and hydrophobic tips were studied, and although a decrease in meniscus size was observed for the hydrophobic tips, all data are consistent with both types of tips resulting in the formation of a meniscus even at 0% relative humidity.