Apparatus suitable for plasma surface treating and process for preparing membrane layers

The invention relates to an apparatus suitable for plasma surface treating (e.g. forming a membrane layer on a substrate) which comprises a plasma generation section (2) which is in communication via at least one plasma inlet means (4) (e.g. a nozzle) with an enclosed plasma treating section (3) which is operable at a lower pressure than the plasma generation section (2), and wherein the plasma treating-section (3) is in communication with inlet means (10) for a fluid (e.g. polymerizable) reactant. The invention furthermore relates to a process for preparing membrane layers employing such an apparatus.