Wetting of Nanopatterned Grooved Surfaces

The wetting by perfluoromethylcyclohexane of a well-defined silicon grating with a channel width of 16 nm has been studied using transmission small angle x-ray scattering. Prefilling, capillary filling, and postfilling wetting regimes have been identified. A detailed comparison of the data with theory reveals the importance of long-ranged substrate-fluid and fluid-fluid interactions for determining the wetting behavior on these length scales, especially at the onset of capillary condensation and in the prefilling regime.

Figure 1

(left) SEM image (top view) of the grating. (inset) Trapezoidal cross-sectional shape. (right) x-ray scattering profile along $q_x$ for the pattern shown on the left.

Figure 2

Filled circles: x-ray scattering intensity of the first-order Bragg peak as function of $\Delta T$ upon heating. Solid line: DFT calculation. Dashed line: DFT calculation including a 10% wide distribution of $D$. Dot-dashed line: geometric construction [5, 19].

Figure 3

Liquid-‐vapor interface in the cavity for prefilling (short-dashed line), capillary filling (solid line), and postfilling (long-dashed line). A circle with radius $R_K$ approximates the meniscus shape for capillary filling.