Nonlinear electronic and ultrafast optical signatures in chemical vapor-deposited ultrathin PtS_(2) ribbons

The emerging two-dimensional(2D)platinum disulfide(PtS_(2))has driven increasing attentions due to its high electron mobility,good air-stability,and strong interlayer interaction which leads to a widely tunable electronic structure.However,a detailed study on its covalent-like layer-dependent properties remains infant.Herein,we demonstrate the successful production of ultrathin 1T-PtS_(2) ribbons with thickness centralized almost at monolayer 1L-4L and large domain size up to 210 μm on Au foils using chemical vapor deposition(CVD)technique,which enables macro-and microscopic study of its extraordinary layer-dependent features with precise control of the number of layers.Using electron energy loss spectroscopy(EELS)and optical pump-probe spectroscopy(OPPS),we reveal that both the electron and ultrafast optical absorption signals of the as-grown 2D PtS_(2) show strong nonlinear layer-dependent responses which manifest discriminated transition in 1L-4L PtS_(2) ribbons.The layer-dependent nonlinear response of 2D PtS_(2) can be well interpreted in the frame of calculated electron and phonon structures.These achievements offer a platform for successfully fabricating large-sized ultrathin 2D PtS_(2) and facilitating our knowledge about its electronic and optoelectronic properties.

An emerging quaternary semiconductor nanoribbon with gate-tunable anisotropic conductance

Two-dimensional noble transition metal chalcogenide(NTMC)semiconductors represent compelling building blocks for fabricating flexible electronic and optoelectronic devices.While binary and ternary compounds have been reported,the existence of quaternary NTMCs with a greater elemental degree of freedom remains largely unexplored.This study presents the pioneering experimental realization of a novel semiconducting quaternary NTMC material,AuPdNaS_(2),synthesized directly on Au foils through chemical vapor deposition.The ribbon-shaped morphology of the AuPdNaS_(2)crystal can be finely tuned to a thickness as low as 9.2 nm.Scanning transmission electron microscopy reveals the atomic arrangement,showcasing robust anisotropic features;thus,AuPdNaS_(2)exhibits distinct anisotropic phonon vibrations and electrical properties.The field-effect transistor constructed from AuPdNaS_(2)crystal demonstrates a pronounced anisotropic conductance(σ_(max)/σ_(min)=3.20)under gate voltage control.This investigation significantly expands the repertoire of NTMC materials and underscores the potential applications of AuPdNaS_(2)in nano-electronic devices.