Ultra-thin 2D transition metal monochalcogenide crystals by planarized reactions

Abstract

We here present a planarized solid-state chemical reaction that can produce transition metal monochalcogenide (TMMC) 2D crystals with large lateral extent and finely controllable thickness down to individual layers. The enhanced lateral diffusion of a gaseous reactant at the interface between a solid precursor and graphene was found to provide a universal route towards layered TMMCs of different compositions. A unique layer-by-layer growth mechanism yields atomically abrupt crystal interfaces and kinetically controllable thickness down to a single TMMC layer. Our approach stabilizes 2D crystals with commonly unattainable thermodynamic phases, such as β-Cu2S and γ-CuSe, and spectroscopic characterization reveals ultra-large phase transition depression and interesting electronic properties. The presented ability to produce large-scale 2D crystals with high environmental stability was applied to highly sensitive and fast optoelectronic sensors. Our approach extends the morphological, compositional, and thermodynamic complexity of 2D materials.

Robust Tunable Large-Gap Quantum Spin Hall States in Monolayer Cu2S on Insulating Substrates

“…Furthermore, the two-sided buckled Cu 2 S ( Figure 1 c), which is energetically more favorable in a freestanding state in comparison to the other two morphologies, will transform into the one-sided buckled phase when it is optimized upon the presence of a substrate, which will be elaborated further in the latter part of the discussion section. Since the one-sided buckled phase is more stable when it is placed on a substrate and has been synthesized recently, 43 we will focus on the electronic and topological properties of the one-sided buckled structure of Cu 2 S.…”

“…Additionally, Chin et al used Cu(111) as a substrate to fabricate the Cu 2 S thin film; therefore, we also simulate the Cu 2 S monolayer on a √3 × √3 supercell of the Cu (4.336 Å) substrate. 43 …”

“… 41 Recently, a β-Cu 2 S monolayer 42 has been synthesized and found to be stable at room temperature. 43 However, the topological properties of Cu 2 S have not yet been fully explored.…”

“…Cu 2 S is an earth-abundant, low-cost, and nontoxic p-type semiconductor with a narrow band gap . Recently, a β-Cu 2 S monolayer has been synthesized and found to be stable at room temperature . However, the topological properties of Cu 2 S have not yet been fully explored.…”

Formation of Ultimate Thin 2D Crystal of Pt in the Presence of Hexamethylenetetramine

“…Atoms’ thick two-dimensional (2D) crystal, particularly graphene-like lattice crystals, have been the focus of attention in the material chemistry synthetic field for the past decade [ 1 ]. With a structure a few atoms thick, this 2D crystal allows an ultimate 2D confinement of the electronic carriers, producing many new phenomena, such as enhancement of exciton formation and robustness [ 2 ], in-plane plasmonic resonance and optical nonlinearity [ 3 ], strong light-mater coupling [ 4 ], thickness and dimension dependent properties [ 5 , 6 ], as well as ultra-fast energy-transfer at the surface [ 7 ].…”