Ž . Surface and Coatings Technology 142144 2001 16 Process control for plasma processing of polymers P. Favia  , M. Creatore, F. Palumbo, V. Colaprico, R. d’Agostino Dipartimento di Chimica, Uni  ersita degli Studi di Bari, Centro di Studio per la Chimica dei Plasmi, CNR, Via Orabona 4, 70126, Bari, ` Italy Abstract PE-CVD processes of a variety of coatings  fluoropolymers, SiO , PEO- and Ag-PEO-like,  COOH functional layers  are x described, as well as plasma treatments aimed to selectively graft  NH groups on polymers, with the use of spectroscopic 2 plasma- and surface-diagnostics parameters of potential use for process transfer and control in industrial applications.  2001 Elsevier Science B.V. All rights reserved. Keywords: Plasma polymers; Process control; Plasma treatments; Actinometry; Surface analysis 1. Plasma processing of polymers Ž . Non-equilibrium low and atmospheric pressure plasmas have a great impact on material science, in that they modify the surface of polymers, as well as of other materials, in ‘cold’ processes that confer on them a tailored surface composition and resultant properties. Ž . Thin film deposition PE-CVD , grafting of chemical Ž . groups, cross-linking plasma treatments , and etching   are the most utilized plasma processes 1  6 ; such processes can be thoroughly understood and optimized in the lab, then duplicated in industrial processes, only when meaningful correlations can be found between Ž the ‘internal’ features of the discharge densitydistri- . bution of species, ion bombardment, etc. , and the final Ž surface property printability, hardness, gas transmis- . sion, blood compatibility, etc. requested in each appli- cation. 2. Plasma and surface diagnostics for process control To study, optimize and transfer a plasma process in different reactors requires extensive use of plasma and  Corresponding author. Fax: 39-080-5443405. Ž . E-mail address: favia@area.ba.cnr.it P. Favia . surface diagnostics, as well as valid material tests. Due to the multivariate relationships existing between the internal characteristics of the discharge, i.e. the key parameters in tuning a process to a requested modifi- Ž cation, and the ‘external’ variables pressure, power, . configuration, etc. adjusted by the operator, reproduc- ing the same set of external variables does not guaran-   tee replication of the process in question 7,8 . This is due also to factors that can change subtly, such as leaks, pumping rate, electrical characteristics of the circuit, etc. Only monitoring in situ the internal parameters with a proper set of diagnostics, and repro- ducing them by tuning the external ones, can guarantee the reproduction of the process and the maximization of the desired surface properties. The same approach allows, obviously, to investigate in detail the fundamen- tal chemistry of the modifications. Optical techniques allow non-intrusive, in situ plasma-diagnostics; actinometric optical emission spec- Ž . troscopy AOES , among them, allows deduction of semi-quantitative density trends of emitting species as a function of the experimental variables, as well as those of electrons of different energies. Provided that electron impact is the main excitation channel, and that the energy excitation thresholds, E , matches for th the emitting species X under scrutiny and for the Ž actinometer i.e. the two species are excited by elec- 0257-897201$ - see front matter  2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 2 5 7 - 8 9 7 2 01 01191-4