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    Thickness-Dependent Structural and Electronic Properties of HfO2 Thin Films Probed by XRD and XAFS
    (Springer, 2025) Ozkendir, Osman Murat; Cengiz, Erhan; Kanmaz, Imran; Gunaydin, Selen; Apaydin, Gokhan; Harfouche, Messaoud
    Hafnium dioxide (HfO2) thin films have garnered significant attention due to their exceptional dielectric, mechanical, and thermal properties, making them ideal for applications in microelectronics, optoelectronics, and energy storage. However, despite extensive research, a comprehensive understanding of their thickness-dependent structural and electronic properties remains incomplete. In this study, we systematically investigate HfO2 thin films (13-115 nm) synthesized via spin coating and characterized using synchrotron-based x-ray absorption fine structure (XAFS) spectroscopy and x-ray diffraction (XRD). High-resolution XRD confirms the monoclinic P2(1)/c phase with high crystallinity and minimal strain, while XAFS analysis reveals thickness-dependent variations in local atomic coordination and electronic structure. XANES spectra demonstrate a systematic shift in the Hf L-3-edge white line, indicating modifications in unoccupied Hf 5d states due to changes in oxygen coordination. EXAFS fitting further quantifies bond distances and coordination numbers, revealing enhanced structural ordering in thicker films. Density functional theory (DFT) calculations corroborate experimental findings, confirming the bandgap (similar to 4.4 eV) and orbital contributions to valence and conduction bands. Our results provide critical insights into defect states, interfacial effects, and thickness-dependent structural modifications, advancing the optimization of HfO2 for next-generation electronic devices.