Ferroelectricity in water ice

Partially proton-ordered ice I (cubic) was grown from the vapor phase, from 40 to nearly 150 K. It is believed to be metastable and oriented by the asymmetry of the solid-vacuum interface during growth. This was studied using a Kelvin (work function) probe for ice grown on a single-crystal Pt(lll) substrate. The ice grows with a slight preference for the O-end aimed away from the surface, with about 0.2% net up dipole per water molecule at 40 K, or about -3 mV/monolayer of deposited ice film. This decreases with deposition temperature as exp(-T/27 K). Near 130, 140, and 150 K sharp features occur as the ice changes from amorphous to crystalline, and dielectric properties became active. By 150 K the effect seems to be zero. These results are discussed in context with other recent reports on ferroelectric ice. In addition to influencing several kinds of vacuum-based studies of ice, this slight ferroelectricity may allow natural ice vapor-grown in space to develop large electric fields.