High-throughput predictions of two-dimensional dielectrics with first-principles calculations

Two-dimensional (2D) dielectrics play a crucial role in the miniaturization of transistors. An optimal 2D dielectric should have a significant out-of-plane dielectric constant and appropriate band alignments to achieve superior performance. However, 2D materials generally exhibit poor out-of-plane dielectric constant. In this paper, we have identified 11 2D materials from the Computational 2D Materials Database with out-of-plane dielectric constants above 5.0, surpassing those of conventional dielectrics, i.e., ${\mathrm{SiO}}_{2}, {\mathrm{Al}}_{2}{\mathrm{O}}_{3}$, and BN. The band alignments show that ten monolayers ${\mathrm{SnNa}}_{2}{\mathrm{H}}_{6}{\mathrm{O}}_{6}, {\mathrm{GeLi}}_{2}{\mathrm{H}}_{6}{\mathrm{O}}_{6}, {\mathrm{HfNa}}_{2}{\mathrm{H}}_{6}{\mathrm{O}}_{6}, {\mathrm{ZrNa}}_{2}{\mathrm{H}}_{6}{\mathrm{O}}_{6}$, etc., are promising dielectrics when monolayer ${\mathrm{MoS}}_{2}/{\mathrm{WS}}_{2}$ serves as the channel. Moreover, four dielectrics have an out-of-plane dielectric constant that outperforms in-plane. This unusual feature indicates a stronger out-of-plane bond strength, resulting from the ionic bonds. We further provide a general guideline for quickly discovering high-performance dielectrics using structures and electronegativity tables.