surface region

https://doi.org/10.1351/goldbook.S06187
The tridimensional region, extending from the free surface of a condensed phase towards the interior, where the properties differ from the bulk. The term @[email protected] may also be used in this sense.
Source:
PAC, 1983, 55, 1251. (Interphases in systems of conducting phases (Provisional)) on page 1253 [Terms] [Paper]