Spontaneous electric fields in films of CF3Cl, CF2Cl2 and CFCl3

Data are presented showing the spontaneous formation of electric fields within solid films of the chlorofluorocarbons (CFCs) CF3Cl, CF2Cl2 and CFCl3 as a function of film deposition temperature from 40 K and above. Electric fields, which arise through dipole alignment and lie in the range of a few times 10(7) V m(-1) to a few times 10(6) V m(-1), decrease as the degree of chlorination increases. Maximum deposition temperatures for display of an electric field lie at similar to 50 K, similar to 65 K and similar to 52 K for CF3Cl, CF2Cl2 and CFCl3 respectively. CFCl3 films possess electric fields which show an onset of temporal metastability between deposition temperatures of 46 K and 50 K. CF3Cl and CF2Cl2 demonstrate temperatures of similar to 65 K and similar to 80 K at which the electric field in the film is removed by heating, so-called Curie points, with decay of the field spread over more than 10 K. CFCl3 displays a comparatively sharp Curie point at 55 K. This variety of behaviour arises despite the resemblance of these three species in terms of electronic structure and gas phase dipole moment, emphasising the requirement for detailed chemical models of this phenomenon.