Track overlap regime in ion-irradiated PMMA

Effect of ion irradiation on the thermal stability of thin polymer films

“…4). This means the roughness evolution is not simply determined by the changes introduced directly by the beam (mainly chain scission and bond breaking at the ester side group [5,17,18]), but it is also dependent on additional thermally activated processes not occurring or that are very slow at room temperature. The roughening process seen at room temperature is also seen at high T, but it is more pronounced for the same level of deposited energy density or fluence.…”

“…At the same time, with further irradiation, the scission products may repolymerize randomly, inducing a cross-linked region that will eventually decrease surface mobility and stabilize the evolution of the topography of the films. The predominance of cross-linking for PMMA bombarded by keV ions at high fluences has been observed in earlier studies [17][18][19]. The substantial loss of side-chain methoxycarbonyl groups at high fluences transform PMMA on a disordered polyethylene-like polymer, for which the probability of cross-linking is higher than scission [17,18].…”

Molecular Depth Profiling with Cluster Ion Beams

“…12,15 The improvement at high temperatures in this particular example is attributed to increased ion beam-induced depolymerization chemistries, more commonly referred to as polymer unzipping. 15,16,86 Polymer unzipping is a process whereby polymers degrade via a rapid main-chain scission process to form lower molecular weight products and monomeric species under high temperature conditions. PMMA, when heated to temperatures greater than ∼360 • C, will rapidly break down to lower molecular weight products and release large quantities of methyl methacrylate (MMA) monomeric species in the process.…”

“…86 For PMMA, for example, polymer unzipping occurs in the temperature range of ∼100-200 • C when being irradiated with 300 keV He + . 86 With cluster sources, this temperature is expected to decrease even further, likely occurring at room temperature for C 60 + and other larger cluster sources. 16 Depolymerization mechanisms can be readily detected through use of a residual gas analyzer (RGA).…”

Electronic Functionality of Nanocomposites

“…Modeling of the ion trajectory and the penetration depth using SRIM numerical simulation (Ziegler et al, 2008) shows that ion tracks critically depend on the irradiation energy parameters as well as the physical and chemical characteristics of the polymer. In general irradiation levels below fluences of 10 13 ions cm -2 produce well separated ion tracks (Fink et al, 1995, Fragala et al, 1998, while fluences above this results in multiple overlapping tracks. Within both the single and overlapping tracks, carbon enriched graphitic clusters become a source of electron transport.…”