Any conceptual region of space restricted in one dimension, within or at the surface
of a condensed phase or a
film. The usage of the term '
film' for an adsorption layer is confusing and is discouraged. The term double-layer applies
to layers approximated by two '
distinct' sublayers.
Source:
PAC, 1994, 66, 1667
(Thin films including layers: terminology in relation to their preparation and characterization
(IUPAC Recommendations 1994))
on page 1671