Electron Spectroscopy Study of Prototypical Organic/Ferromagnetic Spinterfaces for Organic Spintronic Applications

Abstract

This thesis investigates the structural and electronic evolution of organic/ferromagnetic hybrid interfaces, placing particular emphasis on the formation of spinterfaces between 𝛼-sexithiophene (𝛼-6T) and three distinct substrates: Fe, Fe₃O₄, and Co. Such interfaces are central to the development of molecular spintronic devices, as the electronic structures at the organic/metal interfaces can be engineered to influence spin injection and transport. Following an introduction and the establishment of a theoretical background on organic spintronics and spinterface physics, Chapter 3 identifies the experimental techniques employed throughout this work, including atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy (UPS). These complementary surface-sensitive tools enabled a multifaceted analysis of film morphology, interfacial chemistry, and the evolution of electronic structure. Chapter 4 presents a detailed study of the adsorption of 𝛼-6T onto Fe(110). AFM results indicated a Stranski Krastanov growth mode, while XPS/UPS results demonstrated charge transfer and hybridisation effects that developed with coverage. As reported in Chapter 5, the deposition of 6T on Fe₃O₄ under ultra-high vacuum (UHV) conditions produced a transition in molecular orientation from edge-on to head-to-tail packing; these findings were supported by AFM and XPS. The UPS results revealed interfacial screening effects and energy level realignment, confirming the formation of a chemically and electronically active spinterface. Chapter 6 examines 6T/Co, in this context, LEED was not obtainable, but AFM and electron spectroscopy confirmed J-like molecular orientation and weaker hybridisation compared to Fe-based systems. The results underscore the critical influence of substrate properties on molecular adsorption geometry, interfacial electronic states, and overall spinterface behaviour. The findings also highlight how the evolution of molecular coverage affects both orbital structure and interfacial coupling strength, providing a deeper understanding of how organic/metal interfaces can be tuned for spintronic applications. The final chapter combines the main conclusions and proposes future research to advance this field.