A two-stage (primary and processing) [M. Dhayal and J. W. Bradley, Surf. Coat. Technol. 184, 116 (2004)] plasma discharge was used to control the surface chemistry of plasma polymerized acrylic acid (ppAc) films at low ion energy (electron temperature). The discharge conditions in step processing plasma were classified in two regions associated with different distances from the grid separating primary and processing plasmas. The first region showed a steep decrease in electron temperature associated with higher electron collision possibilities with the gas molecules. In the second region a steep decrease in the plasma density that is possibly due to plasma recombination in this region was observed. The analysis of surface chemistry of ppAc films deposited at different positions in these regions was characterized by x-ray photoelectron spectroscopy. In the first region very near the grid results showed that the surface chemistry depends on the neutral or radical diffusing from the primary discharges through the grid. A further increase in the distance from the grid in the first re-ion showed that the energetic electrons' collisions with the gas molecules can significantly change the surface chemistry. The electrons' collisions with the gas molecules can dissociate higher masses into smaller masses. Therefore, an increase in the O/C and -C(=O) functionalities at the surface was measured in this region. In the second region, plasma recombination played a significant role to determine the surface chemistry due to creation of highly reactive radicals and fast neutrals. Therefore, an increase in -COX function was seen at the surface of the films. (c) 2006 American Vacuum Society.