In general, plasma modified polymer surfaces tend to show short aging time and rapid hydrophobic recovery after treatment. To prevent reorientation from the surface to the bulk, appropriate crosslinking is necessary among the polymer chains. In this work, an Ar+ ion beam was used to provide crosslinking to the surface. Crosslinking was shown by spectroscopic ellipsometry, AFM, and FTIR. Contact angle measurements were performed to see the aging of the modified surfaces. The surface modified with Ar+ ion beam followed by RF plasma treatment exhibited reduced chain mobility and a highly stable hydrophilic surface.