Dewetting of thin amorphous solid water films and liquid-cubic ice coexistence in droplets studied using infrared-absorption and secondary-ion-mass spectroscopy

The infrared absorption band of decoupled OD stretching vibration (4 mol% HOD in 20-monolayer H2O) of amorphous solid water is red-shifted and sharpened at around 160 K because of spontaneous nucleation. The crystal grows in a fluidized liquid that forms droplets on a Ni(111) substrate. The shape change and red-shift of a coupled OH band during crystallization are elucidated by a Mie particle scattering model, indicating that nanometer-size droplets are formed preferentially. The spontaneous nucleation at 160 K is bypassed when amorphous solid water is deposited on a crystallized water film; the crystals grow around nuclei at ca. 150 K, resulting in larger crystal grains that do not cause Mie scattering. However, the crystal grains behave like viscous droplets because their morphology changes continuously after the completion of crystallization. The coexisting liquid-like water is indistinguishable from cubic ice in local structure. This behavior resembles that of a quasiliquid formed during premelting.