Berlin 2024 – scientific programme

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DS: Fachverband Dünne Schichten

DS 20: Poster II

DS 20.25: Poster

Thursday, March 21, 2024, 18:00–20:30, Poster D

Understanding the thickness-dependent dielectric permittivity of oxide thin films — •Alessio Zaccone — University of Milan, Department of Physics, 20133 Milan, Italy — Institute of Theoretical Physics, University of Göttingen, Germany

The dielectric properties of thin films are of paramount importance in a variety of technological applications, from thin film capacitors and field-effect transistors to 5G technologies, and of fundamental importance for solid state research. In spite of this, there is currently no theoretical understanding of the dependence of the dielectric permittivity on the thickness of thin films. We develop a confinement model within the Lorentz-field framework for the microscopic Langevin-equation description of dielectric response in terms of the atomic-scale vibrational modes of the solid. Based on this, we derive analytical expressions for the dielectric permittivity as a function of thin film thickness, in excellent agreement with experimental data of Barium-Strontium-Titanate (BST) thin films of different stoichiometry. The theory shows that the decrease of dielectric permittivity with decreasing thickness is directly caused by the restriction in k-space of the available eigenmodes for field-induced alignment of ions and charged groups.

Keywords: dielectric permittivity; dielectric properties of thin films; confinement models; thickness dependent permittivity