Large‐Area Structure‐Selective Synthesis of Symmetry‐Broken MoSe₂ and Their Broadband Nonlinear Optical Response

Abstract

Transition metal dichalcogenides (TMDCs) have various electronic and optical properties depending on their structure, so they can be used as a fascinating material in various applications including photonics, electronics, optoelectronics, and valleytronics. In particular, spiral TMDCs grown through the formation of screw dislocations exhibit novel electronic and optical properties different from layer‐by‐layer TMDCs. However, large‐area structure‐selective synthesis of TMDCs remains challenging. Here, this work reports for the first time the large‐area structure‐selective synthesis of monolayer MoSe2 and spiral MoSe2 using a flux‐controlled chemical vapor deposition method. Under a low MoSe2 flux condition, monolayer MoSe2 is synthesized, whereas thick spiral MoSe2 is synthesized under a high flux condition. Under a medium flux condition, both monolayer and spiral MoSe2 are synthesized. In addition, through the nonlinear optical (NLO) signal analysis of monolayer MoSe2 and spiral MoSe2, the giant enhancement of NLO signals induced by the combined effect of breaking inversion symmetry and the excitonic resonance effects in the synthesized MoSe2 is confirmed. Monolayer MoSe2 and spiral MoSe2 synthesized using this method are expected to be used as advanced optical materials for novel electronics, optoelectronics, and NLO applications.

Two-Dimensional SnSe2(1–x)S2x/MoTe2 Antiambipolar Transistors with Composition Modulation for Multivalued Inverters

“…Since 2004, the novel properties exhibited by atomically thin two-dimensional (2D) materials, characterized by weak interaction along the out-of-plane direction, have transformed the landscape of electronics and optoelectronics. Two-dimensional layered semiconductors like MoS 2 , MoSe 2 and MoTe 2 have gained prominence due to mature large-scale fabrication, thickness-dependent band gap, high carriers’ mobility and effective electrostatic modulation. − The transfer process feasibility for 2D layered semiconductors to an arbitrary substrate enables a facile and clean approach to building artificial van der Waals (vdWs) heterostructures . These vdWs heterostructures can be categorized into straddling (type-I), staggered (type-II), and broken-gap (type-III) based on their band alignments .…”

Epitaxial Growth of Two-Dimensional MoO2–MoSe2 Metal–Semiconductor Heterostructures for Schottky Diodes

“…At the blue dot, the Raman spectrum shows the characteristic peaks of the monolayer MoSe 2 crystal including 239 cm –1 (A 1g ) and 285 cm –1 (E 2g ) . The PL peak located at 1.53 eV corresponds to the A-exciton emission of monolayer MoSe 2 at room temperature. , In the inner parallelogram region, the Raman spectra exhibit several additional peaks observed at 207, 350, 365, 498, 571, and 746 cm –1 . Specifically, the peaks at 571 and 746 cm –1 correspond to the vibrations of the Mo–O 1 and Mo–O 2 bonds, respectively.…”

“…26 The PL peak located at 1.53 eV corresponds to the A-exciton emission of monolayer MoSe 2 at room temperature. 21,27 In the inner parallelogram region, the Raman spectra exhibit several additional peaks observed at 207, 350, 365, 498, 571, and 746 cm −1 . Specifically, the peaks at 571 and 746 cm −1 correspond The microstructures of the heterostructures are explored by HRTEM measurements, as shown in Figure 3b, with a comparison to those of bare MoO 2 (Figure 3a) and MoSe 2 (Figure 3c).…”