Surface Analysis and Ultra‐Shallow Molecular Depth‐Profiling of Polyethylene Treated by an Atmospheric Ar‐D₂O Post‐Discharge

Abstract

In an original approach to trace water reactivity upon surface treatment by ambient “open air” plasma, the H–D exchange processes induced in polyethylene by an Ar‐D 2 O post‐discharge are investigated using time‐of‐flight secondary ion mass spectrometry, both at the surface and along the sample depth. The surface characterization points out the strong influence of the sample‐torch distance. The most important chemical modifications, excluding polymer overheating, occur at 5 mm of distance, with 25% of deuterated monomer units at the surface. For the first time, ultra‐shallow molecular depth‐profiling by Ar noble gas clusters shows the detailed variation of the deuteration of the polymer repeat unit in the topmost surface layer. Our results indicate that the fraction of deuterated monomer units is reduced by a factor >2 over a depth of ∼3 nm.