Phase and Composition Engineering of Self-Intercalated 2D Metallic Tantalum Sulfide for Second-Harmonic Generation

Abstract

Self-intercalation in two-dimensional (2D) materials is significant, as it offers a versatile approach to modify material properties, enabling the creation of interesting functional materials, which is essential in advancing applications across various fields. Here, we define ic-2D materials as covalently bonded compounds that result from the selfintercalation of a metal into layered 2D compounds. However, precisely growing ic-2D materials with controllable phases and self-intercalation concentrations to fully exploit the applications in the ic-2D family remains a great challenge. Herein, we demonstrated the controlled synthesis of self-intercalated H-phase and T-phase Ta 1+x S 2 via a temperature-driven chemical vapor deposition (CVD) approach with a viable intercalation concentration spanning from 10% to 58%. Atomic-resolution scanning transmission electron microscopy-annular dark field imaging demonstrated that the self-intercalated Ta atoms occupy the octahedral vacancies located at the van der Waals gap. The nonperiodic Ta atoms break the centrosymmetry structure and Fermi surface properties of intrinsic TaS 2 . Therefore, ic-2D T-phase Ta 1+x S 2 consistently exhibit a spontaneous nonlinear optical (NLO) effect regardless of the sample thickness and self-intercalation concentrations. Our results propose an approach to activate the NLO response of centrosymmetric 2D materials, achieving the modulation of a wide range of optoelectronic properties via nonperiodic self-intercalation in the ic-2D family.

Atomic engineering of two-dimensional materials via liquid metals

“…Thereinto, phase engineering usually refers to modifying the phase of a 2D material, such as changing between different crystalline structures or transitioning between phases ( e.g. , semiconductor to metal), 232 to tailor its properties for specific applications. 233 Meanwhile, lattice plane engineering focuses on modifying the orientation, spacing, stacking sequence, and symmetry of lattice planes in 2D materials to achieve specific structural and electronic characteristics.…”