Sputtering yields and surface modification of poly(methyl methacrylate) (PMMA) by low-energy Ar+/ CF3+ ion bombardment with vacuum ultraviolet (VUV) photon irradiation

Sputtering yields and surface modification of poly(methyl methacrylate) (PMMA) by mono-energetic ion beams and/or vacuum ultraviolet (VUV) light are studied with the use of a low-energy mass-selected ion beam system. Sputtering yields of PMMA by Ar+ or CF3+ ion beams are obtained as functions of ion incident energy below 500 eV. It is found that surface modification of PMMA due to CF3+ ion incidence is limited to the region near the film surface, whereas that due to Ar+ ion incidence is seen in a relatively deeper region of the film, where PMMA is partially carbonized and diamond-like carbon (DLC) is formed. Under the conditions of incident energies and fluxes of ion and VUV light used in the experiments, the sputtering yield of PMMA by simultaneous incidence of VUV light and CF3+ ions is found to be nearly equal to the sum of the yields by separate incidences of VUV light and CF3+ ions. Some of the etching characteristics observed in this study (such as DLC formation by ion sputtering) may be shared by a wide range of organic polymers that have main chain structures similar to those of PMMA.