Enhanced carrier mobility in MoSe_(2) by pressure modulation

Two-dimensional(2D)materials hold great potential for the development of next-generation integrated circuits(ICs)at the atomic limit.However,it is still very challenging to build high performance devices.One of the main factors that limit the incorporation of 2D materials into IC technology is their relatively low carrier mobility.Thus,the engineering strategies that focus on optimizing performance continue to emerge.Herein,using a spatiotemporal resolved pump-probe setup,the carrier transport performance and relaxation process of few-layer and bulk MoSe_(2) under pressure were investigated nondestructively and simultaneously.Our results show that pressure can tune the transport performance effectively.In particular,under pressure regulation,the carrier mobility of the bulk MoSe_(2) increases by~4 times;meanwhile,the carrier lifetimes of the samples become shorter.Although the processes almost return to their initial state after the pressure release,it is still surprising to see that the carrier mobilities of fewlayer and bulk MoSe2 are still~1.5 and 2 times enhanced,and carrier lifetimes are still shorter than the initial state.Combined with the Raman spectra under pressure,we consider that it is caused by the enhanced layer coupling and lattice compression.The combination of enhanced mobility and shortened lifetime in MoSe_(2) under pressure holds great potential for optoelectronic applications under the deep ocean and deep earth.

Enhanced exciton diffusion from interlayer charge-transfer transitions in PtSe2/MoSe_(2) van der Waals heterojunction

Artificial van der Waals(vdWs)heterostructures offer unprecedented opportunities to explore and reveal novel synergistic electronic and optical phenomena,which are beneficial for the development of novel optoelectronic devices at atomic limits.However,due to the damage caused by the device fabrication process,their inherent properties such as carrier mobility are obscured,which hinders the improvement of device performance and the incorporation of vdWs materials into next-generation integrated circuits.Herein,combining pump-probe spectroscopic and scanning probe microscopic techniques,the intrinsic optoelectronic properties of PtSe_(2)/MoSe_(2)heterojunction were nondestructively and systematically investigated.The heterojunction exhibits a broad-spectrum optical response and maintains ultrafast carrier dynamics(interfacial charge transfer~0.8 ps and carrier lifetime~38.2 ps)simultaneously.The in-plane exciton diffusion coefficient of the heterojunction was extracted(19.4±7.6 cm^(2)∙s^(−1)),and its exciton mobility as high as 756.8 cm^(2)∙V−1∙s^(−1)was deduced,exceeding the value of its components.This enhancement was attributed to the formation of an n-type Schottky junction between PtSe_(2)and MoSe_(2),and its built-in electric field assisted the ultrafast transfer of photogenerated carriers from MoSe_(2)to PtSe_(2),enhancing the in-plane exciton diffusion of the heterojunction.Our results demonstrate that PtSe_(2)/MoSe_(2)is suitable for the development of broadspectrum and sensitive optoelectronic devices.Meanwhile,the results contribute to a fundamental understanding of the performance of various optoelectronic devices based on such PtSe_(2)two-dimensional(2D)heterostructures.