Phase-Controlled Growth of One-Dimensional Mo₆Te₆ Nanowires and Two-Dimensional MoTe₂ Ultrathin Films Heterostructures

Controllable synthesizing of one-dimensional–two-dimensional (1D–2D) heterostructures and tuning their atomic and electronic structures is nowadays of particular interest due to the extraordinary properties and potential applications. Here, we demonstrate the temperature-induced phase-controlled growth of 1D Mo₆Te₆–2D MoTe₂ heterostructures via molecular beam epitaxy. In situ scanning tunneling microscopy study shows 2D ultrathin films are synthesized at low temperature range, while 1D nanowires gradually arise and dominate as temperature increasing. X-ray photoelectron spectroscopy confirms the good stoichiometry and scanning tunneling spectroscopy reveals the semimetallic property of grown Mo₆Te₆ nanowires. Through in situ annealing, a phase transition from 2D MoTe₂ to 1D Mo₆Te₆ is induced, thus forming a semimetal–semiconductor junction in atomic level. An upward band bending of 2H-MoTe₂ is caused by lateral hole injection from Mo₆Te₆. The work suggests a new route to synthesize 1D semimetallic transition metal chalcogenide nanowires, which could serve as ultrasmall conducting building blocks and enable band engineering in future 1D–2D heterostructure devices

Intrinsic polarization conversion and avoided-mode crossing in X-cut lithium niobate microrings

Compared with well-developed free space polarization converters, polarization conversion between TE and TM modes in waveguide is generally considered to be caused by shape birefringence, like curvature, morphology of waveguide cross section and scattering. Here, we reveal a hidden polarization conversion mechanism in X-cut lithium niobate microrings, that is the conversion can be implemented by birefringence of waveguides, which will also introduce an unavoidable avoided-mode crossing. In the experiment, we find that this mode crossing results in severe suppression of one sideband in local nondegenerate four-wave mixing and disrupts the cascaded four-wave mixing on this side. Simultaneously, we proposed, for the first time to our best knowledge, one two-dimensional method to simulate the eigenmodes (TE and TM) in X-cut microrings, which avoids the obstacle from large computational effort in three-dimensional anisotropic microrings simulation, and the mode crossing point. This work will provide an entirely novel approach to the design of polarization converters and simulation for monolithic photonics integrated circuits, and may be helpful to the studies of missed temporal dissipative soliton formation in X-cut lithium niobate rings

Animate field of 1.1THz

The broadband mechanism in the high-frequency band results from the coupling of Mie resonances in dielectric wires excited by the incident wave to the graphene plasmon resonances. In this visualization, we take the animate field of 1.1 THz for example to show the absorption process

Electron-Doping-Enhanced Trion Formation in Monolayer Molybdenum Disulfide Functionalized with Cesium Carbonate

We report effective and stable electron doping of monolayer molybdenum disulfide (MoS₂) by cesium carbonate (Cs₂CO₃) surface functionalization. The electron charge carrier concentration in exfoliated monolayer MoS₂ can be increased by about 9 times after Cs₂CO₃ functionalization. The n-type doping effect was evaluated by <i>in situ</i> transport measurements of MoS₂ field-effect transistors (FETs) and further corroborated by <i>in situ</i> ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and Raman scattering measurements. The electron doping enhances the formation of negative trions (<i>i.e.</i>, a quasiparticle comprising two electrons and one hole) in monolayer MoS₂ under light irradiation and significantly reduces the charge recombination of photoexcited electron–hole pairs. This results in large photoluminescence suppression and an obvious photocurrent enhancement in monolayer MoS₂ FETs