203 2 archive 6 disk0/00/00/02/03 2009-01-20 2009-06-22 11:44:43 2009-04-08 16:55:54 report show 0 Charpin Jean Cregan Vincent Gleeson James Hayes Michael Lee William O'Brien Stephen Vynnycky Michael unpub other esgi62 CRANN public CRANN researchers are interested in mathematical modelling of all aspects of the process of spin-coating of diblock copolymers, with the aim of removing expensive trial and error design cycles. Of particular interest is the flow of the polymer during spin-coating, and also during the subsequent annealing process. Also of considerable interest is the chemical process of phase-separation and self-assembly of the diblock copolymer. Existing models in the literature rely heavily on computationally expensive Monte-Carlo simulation methods. The modelling work performed during the study group in summarized in this report. The report is split into four main sections, with discussion and suggestions for experiments in the concluding section. The content of the sections is as follows: Section 0.2: Mathematical modelling of spin-coating onto a flat substrate; no annealing considered. Section 0.3: Modelling of spin-coating onto a substrate with topography (i.e. trenches); no annealing considered. Section 0.4: Flow of polymer during annealing. Section 0.5: Models for self-assembly of polymers into nanostructures. Sections 0.2 to 0.4 are focussed on the fluid flow problems for the polymer, and go some way to providing useful answers to Problem 1. On the other hand, Problem 2 was found to be extremely challenging, and the efforts described in section 0.5 represent only a relatively modest impact on this problem. Diblock copolymer thin films have attracted significant recent interest because of their potential applications in nanofabrication. Diblock copolymers are macromolecules consisting of two chemically distinct polymer chains covalently bonded together at one junction point. It is well-known that a molten collection of these molecules microphase segregates below an order-disorder transition temperature (ODT) to form a myriad of interesting nano/microstructures [1]. In the process under study, various diblock copolymers are dissolved in solvent and spin-coated onto a patterned silicon wafer. Several possible configurations for the trenches are employed, see Figure 1 below. The nanostructured films then undergo athermal anneal at 200°C for up to 24 hours, and the polymer phase-separates and selfassembles into well defined nanostructures with periodicities approaching 10 nm. Problem 1: Describe how the spin-coating process is affected by the geometrical configuration of trenches (see side profiles in Figure 3). How should parameters be adjusted to optimize quality of trench-filling (so over-filling or under-filling are avoided or minimized)? Problem 2: Model the effects (on both the thin-film flow and on the phase separation dynamics) of different chemical functionalities introduced through surface treatments. These may include hydrophobic and hydrophilic surfaces, or neutral (to the polymer blocks) surfaces laid in alternating patterns to influence the morphology of the confined melt. Known models for the pattern formation process include a selfconsistent field theory approach [2], Monte Carlo simulations [3], and phenomenological models [4]; see also the review [1]. 2008 published 25 [1] Section IV of A.K. Chakraborty and A.J. Golumbfskie, Annual Review of Physical Chemistry, 52, 537 (2001). [2] D. Petera and M. Muthukumar, J. Chem. Phys. 109, 5101 (1998). [3] Q. Wang, S.K. Nath, M.D. Graham, P.F. Nealey, J.J. de Pablo, J. Chem Phys. 112, 9996 (2000). [4] G.G. Pereira and D.R.M. Williams, Phys. Rev. Lett. 80, 2849 (1998). 199 1 203 1 application/pdf en public

crann-2.pdf

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