  Ice nucleation from vapor presents a variety of challenges across a wide
range of industries and applications including refrigeration, transportation,
and energy generation. However, a rational comprehensive approach to
fabricating intrinsically icephobic surfaces for frost formation-both from
water condensation (followed by freezing) and in particular from desublimation
(direct growth of ice crystals from vapor)-remains elusive. Here, guided by
nucleation physics, we investigate the effect of material composition and
surface texturing (atomically smooth to nanorough) on the nucleation and growth
mechanism of frost for a range of conditions within the sublimation domain (0 C
to -55C; partial water vapor pressures 6 to 0.02 mbar). Surprisingly, we
observe that on silicon at very cold temperatures-below the homogeneous ice
solidification nucleation limit (< -46 C)-desublimation does not become the
favorable pathway to frosting. Furthermore we show that surface nanoroughness
makes frost formation on silicon more probable. We experimentally demonstrate
at temperatures between -48 C and -55 C that nanotexture with radii of
curvature within one order of magnitude of the critical radius of nucleation
favors frost growth, facilitated by capillary condensation, consistent with
Kelvin's Equation. Our findings show that such nanoscale surface morphology
imposed by design to impart desired functionalities-such as
superhydrophobicity-or from defects, can be highly detrimental for frost
icephobicity at low temperatures and water vapor partial pressures (< 0.05
mbar). Our work contributes to the fundamental understanding of heterogeneous
phase transitions well within the equilibrium sublimation domain and has
implications for applications such as travel, power generation, and
refrigeration.
