Low-energy-barrier ferroelectric in monolayer CdX (X = Se and Te) and their potential applications in electrical device and photocatalyst: A first-principles study

Abstract

Ferroelectric materials exhibit switchable spontaneous polarization and provide significant potential in advanced electronics. This study employs density functional theory to investigate two-dimensional (2D) CdX (X = Se and Te) monolayers, which possess an asymmetric buckled structure leading to out-of-plane spontaneous polarization. The results show that both CdSe and CdTe monolayers are semiconductors with favorable bandgaps (1.35 and 1.32 eV) and exhibit spontaneous polarizations of 9.13 and 9.27 pC/m, respectively. The energy barriers of CdSe and CdTe monolayers are very low (17 and 57 meV) and their polarization direction can be switched by applying a low electric field of ∼0.3 V/Å. At a thickness of 4 nm, CdSe and CdTe monolayers possess tunneling electroresistance of 7.18 and 6.44, respectively, revealing significant potential for ferroelectric tunnel junction applications. Furthermore, the strong redox capability of photogenerated carriers endows CdX (X = Se and Te) monolayers well-suited for photocatalytic applications in all acid–base solutions (pH = 0–14). These results reveal that CdX (X = Se and Te) monolayers are remarkable ferroelectrics for applications in nanoelectronics and photocatalysts.