The understanding of the nucleation stage of thin film growth is a key element of the optimization of synthesis parameters in order to obtain high-quality optical coatings with predetermined characteristics. The fabrication of advanced coatings, often consisting of complex non-quarter wave and/or metal dielectric stacks, requires new and more powerful in situ monitoring techniques compared to conventional reflectometry and transmission, or quartz crystal microbalance measurements. We describe the use of in situ real-time spectroscopic ellipsometry (RTSE) for the development of optical materials and for the control of the fabrication of homogeneous and inhomogeneous optical filters. Examples include materials such as Ti02, Si02 and SiNx prepared by plasma-enhanced chemical vapor deposition (PECVD).
Molecular orientation plays a significant role in determining the performance of small molecule solar cells. Key photovoltaic processes in these cells are strongly dependent on how the molecules are oriented in the active layer. We isolate contributions arising from the bulk molecular orientations vs. those from interfacial orientations in ZnPc/C60 bilayer systems and we probe these contributions by comparing device pairs in which only the bulk or the interface differ. By controlling the orientation in the bulk the current can be strongly modulated, whereas controlling the interfacial molecular orientation and degree of intermixing mediate the voltage.