[TuP3E] E. Physics, spintronics, and novel device concepts

[TuP3E-09] Development of an Evaluation Method for Spatial Distribution of Permittivity

〇Hayato Kobayashi¹, Akira Sumiyoshi¹, Ranferi Cancino Betancourt¹, Shota Sato¹, Jun Nakamura¹ (1. The University of Electro-Communications (Japan))

We investigated the local dielectric constant distribution of hydrogen-terminated cubic boron nitride (c-BN) (111) thin films using first-principles calculations based on density functional theory (DFT). c-BN is a promising wide-bandgap semiconductor sharing the same crystal structure as diamond. While the bulk dielectric constant is well-established, local variations in atomic-scale films remain unclear. We evaluated the dielectric profile along the surface normal for films ranging from 1 to 10 bilayers by analyzing induced charge distributions under finite electric fields.Our results show that in thick films, the dielectric constant at the center converges quantitatively to the bulk value derived from density functional perturbation theory. However, a significant enhancement is observed near the nitrogen-terminated (N-face) surface. Band structure analysis reveals that this enhancement originates from near-free electron (NFE) states localized at the conduction band minimum on the N-face. This phenomenon is analogous to the NFE-driven dielectric enhancement previously reported in hydrogen-terminated diamond surfaces. These findings suggest that the energetic alignment of NFE states is a critical factor governing the local dielectric properties of hydrogenated wide-bandgap semiconductor surfaces, providing essential insights for c-BN-based device interface design.