Application of high energy ion scattering techniques to the investigation of iron oxide surfaces and interfaces

Full text: Thin films of iron oxide with good crystalline quality are extremely important in several applications including catalysis, magnetic thin films and integrated microwave devices. The structural and chemical properties of the surfaces and the film-substrate interface are vital in growing such high quality films. High-energy ion scattering techniques (Rutherford backscattering and channeling) have been widely used to characterise interfacial solid-solid interaction, determine crystal structure at buried interfaces and analyse for extended defects that may arise in growth procedures. In the present work, we have investigated the properties of the surfaces and film-substrate interface of epitaxially grown thin films of α-Fe2O3(0001) (hematite) on α-AI2O3(0001) using the Rutherford backscattering and channeling techniques. Experiments were carried out at the EMSL accelerator facility. The channeling spectrum corresponds to 700 A thick film shows three peaks, which correspond to Fe atoms open to ion beam at the surface, at the interface and Al atoms at the interface. Since the Fe and Al atoms are visible to ion beam at the interface, there must be some disordering of the ion oxide film at the interface or substrate-film mixing present at the interface. High-resolution transmission electron microscopy (TEM) measurements from the same sample show periodic misfit dislocations at the interface corresponding to approximately the lattice mismatch between the substrate and the film. Molecular dynamics simulations (MD) were performed in order to understand the formation of misfit dislocations and interface structural features of Fe2O3 on AI2O3 system. Simulations were performed using the VEGAS code with the atomic positions generated by the MD calculations and were compared to experimental surface peak areas to investigate the structure of the surface and the interface of these films