| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Thin Films | Wednesday Sessions |
| Session TF-WeM |
| Session: | Plasma-based Film Growth, Etching, & Processing |
| Presenter: | Andrew Michelmore, University of South Australia, Australia |
| Authors: | A. Michelmore, University of South Australia, Australia S. Saboohi, University of South Australia, Australia B.R. Coad, University of South Australia, Australia R.D. Short, University of Lancaster, UK H.J. Griesser, University of South Australia, Australia |
| Correspondent: | Click to Email |
There is increasing need for fabrication of thin polymeric films with complex chemical functionality for a variety of applications including cell therapies, biosensing, microelectronics and as platforms for surface initiated atom-transfer radical polymerization (ATRP). Conventional polymerisation techniques are not suitable in many instances as control of film thickness and topography is difficult. Plasma polymerisation is a technique which can overcome these issues, but has typically suffered from difficulty in retaining chemical structure due to fragmentation in the plasma phase and/or ion bombardment on the surface.
We have shown that pressure plays a critical role in plasma processes. By tuning the plasma from collisionless to collisional sheaths (the alpha to gamma transition) the chemistry of the plasma and the plasma polymer are drastically changed [1]; in gamma mode, the plasma chemistry is biased towards protonated precursor ions and the contribution of ions to the deposit increases. For example, we have studied deposition of ethyl a-bromoisobutyrate (EBIB) for fabricating surfaces for initiating ATRP [2]. This requires that the intact a-bromoisobutyryl structure be retained on the surface of the plasma polymer. Using plasma phase mass spectrometry we show that at the transition from alpha to gamma mode protonated EBIB are formed which arrive at the surface intact and dominate the deposition process. This results in high retention of groups capable of initiating ATRP. High pressure also limits the ion energy, such that ions can be ‘soft landed’ and do not scramble chemical structures on the surface by ion bombardment.
More recent results on a family of ester compounds will be presented which highlight the critical roles of pressure, power and ion energy. Methods for predicting optimum conditions will also be discussed. These results open possibilities to fabricate functionalized surfaces with higher retention of chemical structure than has been possible previously.
1.Saboohi, S.; Jasieniak, M.; Coad, B.R.; Griesser, H.J.; Short, R.D.; Michelmore, A.; Comparison of Plasma Polymerization under Collisional and Collision-Less Pressure Regimes, J. Phys. Chem. B, 2015, 119, 15359−15369
2. Saboohi, S.; Coad, B.R.; Michelmore, A.; Short, R.D.; Griesser, H.J. Hyperthermal Intact Molecular Ions Play Key Role in Retention of ATRP Surface Initiation Capability of Plasma Polymer Films from Ethyl α‑Bromoisobutyrate, ACS Appl. Mater. Interfaces, 2016, 8, 16493−16502