[(a) and (b)] Topographic AFM images obtained in acoustic (tapping) mode of surfaces obtained by cleavage along the and directions, respectively. All images were taken at and . Schemes showing the relevant directions, crystallographic and cleavage, are shown on top of the images. (c) Histogram of the distribution of angles between and other step directions for surfaces cleaved along the direction. (d) Representation of triangular steps on a surface forming angle of 15° (left) and 30° (right), respectively. Fluorine and barium ions are represented by green and yellow balls, respectively, while the surface is represented by gray balls.
Topographic (left) and phase (right) AFM images taken at ambient conditions ( and ) in acoustic (tapping) mode of a surfaces obtained by cleavage along: (a) the direction and (b) and (c) the direction]. In (c) steps running along and are indicated by A and B, respectively, highlighting different wettability behavior.
(a) Topographic AFM images obtained in acoustic (tapping) mode of surfaces obtained by cleavage along the directions. The images, (1)–(3), show the evolution after sequential scanning on the same region. The acquisition time per image is 170 s. Image (4) corresponds to a zoom of the central region of (1). The perturbation induced by the scanning tip can be observed in the formation of the different structures. (b) SPFM (left) and KPFM (right) images taken on a surface. All images were taken at and 50% RH.
(a) Phase AFM images of the evolution with increasing water coverage of water film structures on a highly stepped surface. Images were taken at RT and . Increasing water coverage was induced by the AFM tip. (b) Optical microscopy images of a surface obtained by cleavage along the direction. Images were taken at constant ambient and variable sample temperatures, indicated in the figure. As temperature decreases the relative humidity close to the surface increases and water adsorbs on the surface forming patterns very similar to the patterns formed by water bilayer patches observed using AFM.
(a) Phase AFM image obtained in acoustic (tapping) mode of a surface obtained by cleavage along the direction. The image shows a detail of a water meniscus between two steps forming an angle of 15° evidencing two different contact angles. At the step along the crystallographic direction the contact angle is lower (more hydrophilic) than at the step at 15° from this direction. A scheme indicating the relevant angles and directions is shown in (b).
Topographic AFM images obtained in acoustic (tapping) mode of surfaces obtained by cleavage and then immersed in water for different times: 20 s, 1 min, 5 min, and 60 min. For immersion times higher than 15 s triangular pits produced by water etching can be observed. The directions of the triangles correspond to crystallographic directions. For large immersion times triangular as well as hexagonal step structures can be observed. All images were taken at RT and low humidity conditions .
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