| AVS 54th International Symposium | |
| Thin Film | Thursday Sessions |
| Session TF2-ThA |
| Session: | Computational Aspects of Thin Films |
| Presenter: | S.B. Sinnott, University of Florida |
| Authors: | W.-D. Hsu, University of Florida S. Tepavcevic, University of Illinois at Chicago L. Hanley, University of Illinois at Chicago S.B. Sinnott, University of Florida |
| Correspondent: | Click to Email |
Density functional theory-MD (DFT-MD) simulations are used to study surface polymerization by ion-assisted deposition (SPIAD) of thiophene on alpha-terthiophene oligomers on a silicon surface to determine the dominant mechanisms responsible for the SPIAD process. Polythiophene is a conductive polymer that has attracted much interest in recent years because its properties are desirable for applications that include light emitting diodes, field effect transistors, and photovoltaics. Optimization of the performance of polythiophene in these devices requires the development of processing methods that can simultaneously control its chemistry and morphology on the nanometer scale. One such method is SPIAD, where conducting polymer thin films are grown on substrates by the simultaneous deposition of hyperthermal polyatomic ions and thermal neutrals in vacuum. Both neutral and positively charged systems are considered in the DFT-MD simulations in order to assess the effect of charge on the results, which were compared to experimental data. The incident energies range from 100 to 500 eV. The simulations indicate that the differences in the collision outcomes between the neutral and positively charged events are small in most cases, but the atoms in the +1 charged system experienced slightly larger forces and velocity variations than the atoms in the neutral system. Several key bond dissociation and polymerization mechanisms are predicted in the simulations that are also observed experimentally. The most important prediction is that incident thiophene ions break apart on collision with the 3T film. Both the experiments and simulations indicate that incident thiophene ions chemically modify the structure of the oligomer film by covalently bonding to the 3T oligomers. The insight gained from this integrated experimental and computational work can be used to optimize the SPIAD process for polythiophene and other conducting polymer systems. This work is supported by the National Science Foundation (CHE-0200838).