Regensburg 2025 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 18: Materials Research in Polar Oxides: Perspectives for Optics & Electronics

KFM 18.4: Talk

Thursday, March 20, 2025, 16:45–17:00, H9

Atomistic Modelling of Ferroelectric Bonded Structures — •Nils Andre Schäfer and Simone Sanna — Institute for Theoretical Physics, Justus Liebig University Giessen, Germany

Direct bonding in ferroelectric materials, such as lithium niobate (LN), provides a method to create both head-to-head (H2H) and tail-to-tail (T2T) domain walls (DWs). These DW configurations are particularly interesting due to their ability to exhibit (semi-)metallic behavior by the formation of a two-dimensional electron or hole gas. This phenomenon enables the creation of localized conducting areas within an otherwise wide-gap semiconductor material.

In this work, we model H2H and T2T bonded structures within DFT. Therefore, we start with the thermodynamically stable z-cut surfaces of LN. Simulations were conducted on slabs with varying film thickness to minimize the surface interactions before constructing the bonded structures. The energy landscape of the interface was mapped by systematically translating the films relative to each other and analyzing various quantities, such as free charge carrier densities, the film distance, and the surface energy. In conclusion, H2H and T2T bonded structures exhibit distinct morphological and electronic interfaces, resulting in variations in their expected conductivities.

Keywords: lithium niobate; lithium tantalate; direct bonding; DFT