| AVS 58th Annual International Symposium and Exhibition | |
| Thin Film Division | Monday Sessions |
| Session TF-MoM |
| Session: | Thin Films: Growth and Characterization I |
| Presenter: | Gianfranco Aresta, Eindhoven University of Technology, Netherlands |
| Authors: | G. Aresta, Eindhoven University of Technology, Netherlands J. Palmans, Eindhoven University of Technology, Netherlands M.C.M. van de Sanden, Eindhoven University of Technology, Netherlands M. Creatore, Eindhoven University of Technology, Netherlands |
| Correspondent: | Click to Email |
The state-of-the art approach in the encapsulation of high-end devices such as flexible (polymer) solar cells and organic light emitting diodes against water vapour permeation is an organic/inorganic multi-layer system. Although this approach allows increasing the lifetime of the encapsulated device, the optimization of a multi-layer is rather empirical as the mechanisms behind the improvement of the barrier performance are not yet unraveled. In particular, the role of the organic interlayer is rather controversial since effectively it does not act as a moisture vapor barrier, yet its application appears to be fundamental in the multi-layer solution. In this contribution, the role of the organic interlayer is investigated by selecting a system in which the barrier layer, a 100 nm-thick SiO2 film, is plasma- deposited while the organic interlayer, a 200 nm- thick organosilicon film, is synthesized by means of initiated- chemical vapor deposition, i.e. via thermal decomposition of an initiator molecule promoting the polymerization of 1,3,5-trimethyl-1,3,5-trivinyl-cyclotrisiloxane (V3D3) at the substrate.
The implementation of in situ (real time) spectroscopic ellipsometry allows following the different growth stages in the V3D3 polymerization process. In particular, when applied to the polymer bulk growth, the determination of the growth rate allows monitoring the transition from a kinetic-limited (with activation energy of 65 ± 4 kJ/mol) to a mass transfer-limited regime. Furthermore, the deposition process is found to be monomer adsorption- limited with an activation energy of -39 ± 4 kJ/mol. When spectroscopic ellipsometry is applied to the initial monomer adsorption steps, isothermal adsorption/desorption studies provide insight into the microstructure of the underlaying SiO2 barrier layer, characterized by a residual open porosity in the micro/meso transition region (pore radius ≤ 2nm). The microstructure characterization by means of the above-mentioned studies implicitly points out the role of the i-CVD organic interlayer in multi-layer barrier structures, i.e. the filling of the open micro-meso porosity of the inorganic barrier layer, therefore, improving the intrinsic barrier quality of the underlaying SiO2 film. This outcome nicely correlates with the superior water vapor barrier performances (a barrier improvement factor of 2400 is reported with respect to the pristine polymer) of multi-layers based on the application of i-CVD organic interlayers with respect to fully-PECVD developed multi-layers.