Figure 1
From: Interface-Induced Ordering of Gas Molecules Confined in a Small Space
FM-AFM measurements of a HOPG-water interface after oxygen-supersaturated water was deposited.
(a) Topographic image acquired at t = 300 min. A cap-shaped nanostructure marked with “+” serves as a marker for comparison with other images. (b) Higher-resolution height image of a region around the cap-shaped nanostructure marked with “+” acquired at t = 310 min. Because of the large height variation of various structures, the contrast of the row-like patterns in the base layers cannot be clearly shown. (c) Topographic image of a similar area acquired at t = 205 min. The region outlined by white lines was later covered by a thick disordered layer, as indicated by the white arrow in (a) and (b). In the ordered base layers, two sets of row-like structures existed; one set was oriented along a zigzag direction (indicated using pink arrows) of the HOPG substrate and the second was oriented along an arm-chair direction (indicated using blue arrows). The green arrow indicates areas with a disordered molecular layer. (d) Dissipation image acquired simultaneously with the image shown in (c). We note that primarily flat terraces and substrate step edges were observed when pre-degassed water was deposited on clean HOPG36,37,38. Domains of monolayer row-like patterns might appear, but the coverage was typically less than 10% of the interface after 8 hours of water deposition. Thus the 2D and 3D patterns shown here were produced by oxygen accumulating at the interface.
