Defect Engineering of Out-of-Plane Charge Transport in van der Waals Heterostructures for Bi-Direction Photoresponse

Abstract

Defects are ubiquitous in two-dimensional (2D) transition-metal dichalcogenides (TMDs), generated by the initial growth- or the postprocessing. However, the defects may play negative roles in the photoelectronic properties of TMDs due to the reduction of in-plane transport of carriers. In this work, we demonstrate that the Se-vacancy defects in MoSe2 side of the van der Waal heterostructure is able to switch direction of out-of-plane charge transport. Photoresponse spectra showed defect density enable modified surface potential of MoSe2–x , leading to the barrier reverse between graphene and MoSe2–x and switches of the photoresponse from the negative to the positive. This unexpected property stemmed from appearance of midgap states by defects at heterostructure, as demonstrated by the density functional theory calculation and scanning tunneling microscope results. MoSe2–0.2/graphene heterostructure has a broadband response ranging from 450 to 1064 nm and exhibits comparable or higher positive responsivity (5.4 × 103 A/W to −15.3 × 103 A/W at 632.8 and 5.7 × 103 A/W to −1.2 × 103 A/W at 1064 nm) to the negative one of the pristine MoSe2/graphene. Based on defect-engineered heterostructures, we construct optoelectronic OR and AND logic devices with a broadband operation. Our work elucidates an alternative avenue to tailor the out-of-plane charge transport in TMD-based heterostructure through defects, and potentially invokes applicable utilization for 2D photodetectors and optoelectronic logic gates.

Morphological dependent exciton dynamics and thermal transport in MoSe2 films

“…Where, is the Boltzmann constant, T is the temperature (in Kelvin), 𝑥 = The nonlinear temperature dependency of Raman shifts is then fitted using equation (8) to equation (11) as done in our recent study on MoS 2 . 38 The contributions from the processes of thermal expansion, three-phonon, and four-phonon scatterings for both morphologies of MoSe 2 parameter and thermal expansion coefficient =10.510 -5 K -1 are taken for A 1g mode of 𝑇 MoSe 2 from literature.…”

“…9 This defect tunability in CVD-grown MoSe 2 can be utilized for the development of new quantum light sources such as SPEs, exible nano-electronics, and optoelectronic devices. 10,11 Integrated electronic circuits, made with millions of transistors, generate excess heat during operation, which affects the performance and stability, leading to the probable failure of the device. Hence, it is important to understand the thermal transport behaviour of MoSe 2 for the development of its devices.…”

Defect engineering in conjugated polyimides for promoting visible-light-driven photocatalytic benzylamine oxidation

“…24,25 Defect engineering of materials can improve the above shortcomings to a certain extent, because the introduction of defects can lead to the breakage and reformation of some chemical bonds, achieve a localized distribution of electrons, enhance the carrier separation and migration properties, and thus can regulate the energy band, electronic structure and specific surface area of a catalyst. [26][27][28][29][30][31][32][33][34][35] Nevertheless, there are few studies on the defect engineering of polyimide materials. 36,37 Therefore, the development of defective polyimide-based derivatives has a great importance for further expanding the field of polyimide materials.…”

Schottky‐Contacted High‐Performance GaSb Nanowires Photodetectors Enabled by Lead‐Free All‐Inorganic Perovskites Decoration

“…[36] At the same time, the energy bands of semiconductors NWs near surface usually bend upwards or downwards, resulting in the designed barrier heights. [37,38] In short, with the controlled barrier thicknesses and heights, the expected Schottky-contacts or Ohmic contacts between NWs and metals electrodes can be achieved for high-performance optoelectronics or electronic devices.…”