Optical and complex dielectric function of (100) SrTiO3 single crystals derived from valence EELS and Kramers-Kronig analysis

Strontium titanite with a perovskite structure is widely studied for its dielectric and optical properties and is also used as a functional oxide in dielectric layers and epitaxial substrates relevant to semiconductor-related processing environments. In this context, the present work provides an experiment-linked reconstruction of optical and dielectric response derived from valence EELS. It is important to mention that in a single crystal they are often used to discover where the properties originate because they have no grain boundaries or pores. Accordingly, a single-crystal platform enables the evaluation of intrinsic and local electronic response without microstructural contributions. This study investigates the optical and dielectric response of a (100) Nb-doped SrTiO 3 single crystal using valence EELS and Kramers-Kronig analysis (KKA) to reconstruct the complex dielectric function. Here, SrTiO 3 is addressed as a wide-bandgap functional oxide rather than as a conventional semiconductor material. The optical response shows a static refractive index of about n(0) = 2.37, a static dielectric constant of ε STO = 5.63, and a band-edge onset at E g = 2.25 eV (derived from the VEELS/KKA optical response). Cole-Cole analysis reveals a broad range of dielectric relaxation processes, suggesting complex polarization behavior tied to a distributed relaxation-time spectrum and heterogeneous polarization dynamics within the probed region. The spectra also show the plasmonic and the interband-transition regions. • VEELS/KKA derive optical and complex dielectric response of (100) Nb-doped SrTiO 3 . • Single-crystal (100) platform enables intrinsic/local response assessment. • Static refractive index from VEELS/KKA: n(0) = 2.37. • Complex dielectric function reconstructed by Kramers-Kronig analysis (KKA). • Cole-Cole separates Total Complex Dielectric Response and Local Dispersive Contribution.