Submission note: "A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy [to the] Department of Physics, School Of Engineering and Mathematical Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora"
Organic molecules provide unique electronic properties that offer immense possibilities to future electronic device industries. Semiconductor materials consisting of molecular building blocks can be customised with distinct functional properties and have already found their way into state-of-the-art devices for applications such as optoelectronics and photovoltaics. Further advancements in the performance and efﬁciencies of these devices necessitates a thorough understanding of the interfacial energy level alignment and interfacial structure resulting from surface transfer doping. The ﬂuorofullerenes are very efﬁcient molecular acceptors on account of their high electron afﬁnity, providing a model molecular system for the study of surface doping of underlying materials because the doping process may proceed with submonolayer ﬂuorofullerene coverages.The thesis presents synchrotron based photoemission investigations that elaborate the energy level alignment of ﬂuorofullerene molecules on zinc-tetraphenylporphyrin (ZnTPP) and copper-phthalocyanine (CuPc) ﬁlms. High-resolution core level photoelectron spectroscopy was used to identify and to follow the evolution with coverage of two distinct charge states of adsorbed ﬂuorofullerene molecules: charged molecules that participate in the charge transfer process and neutral molecules that do not. The relative intensity of the two molecular species was used to determine the molecular doping efﬁciency and applied to develop an integer charge transfer model to quantify the doping process and explore the organic energy level alignment. These experiments and the resulting doping model were further extended to consider the energy level structure at the interface of C60F48 and graphene. Here, intrinsically n-doped epitaxial graphene on Si(0001) and neutral ’quasi-free standing’ graphene were shown to develop p-type conductivity upon ﬂuorofullerene deposition. Complementing the knowledge of the energy level structure at ﬂuorofullerene interfaces, low temperature scanning tunnelling microscopy (STM) was used to explore the structural behaviour of C60F48-ZnTPP and C60F48-Au(111) interfaces. For the case of the C60F48-ZnTPP interface, the ﬂuorofullerene adlayer was found to be randomly arranged and the underlying ZnTPP ﬁlm ordered for the case of multilayer ﬁlms. For the C60F48-Au(111) interface, ordered adlayers of C60F48 were identiﬁed, including a new, distinct orientationally ordered ’ﬂoral’ state of C60F48.
The thesis author retains all proprietary rights (such as copyright and patent rights) over the content of this thesis, and has granted La Trobe University permission to reproduce and communicate this version of the thesis. The author has declared that any third party copyright material contained within the thesis made available here is reproduced and communicated with permission. If you believe that any material has been made available without permission of the copyright owner please contact us with the details.