Oxygen-Assisted Anisotropic Chemical Etching of MoSe₂ for Enhanced Phototransistors

Abstract

The etching process can serve as an effective top-down approach that facilitates direct construction of tuned patterns, reversely studying growth mechanisms and further inducing unexpected physical properties. Currently, etching behaviors of monolayer transition-metal dichalcogenides (TMDs) have been rarely explored and the intrinsic etching mechanism still needs to be fully elucidated. Here, we demonstrate a facile and controllable oxygen-assisted anisotropic chemical etching of two-dimensional (2D) materials. Taking MoSe2 as an example, a series of well-defined etched patterns can be fabricated by precisely modulating the pretreatment time of oxygen plasma and the etching time. Atomic characterization exhibits that the edges of etched patterns are mainly zigzag-terminated. Density functional theory calculations highly agree with the experimental results, indicating an energy preference for zigzag edges. The as-produced MoSe2 flakes can be used as part of heterojunctions to display intriguing optoelectronic properties. The field-effect transistor based on as-etched MoSe2 flakes and the 2D poly­(3-hexylthiophene-2,5-diyl) crystal shows a distinct enhanced ambipolar photoresponse. Our strategy offers a new direction for preparing patterned 2D TMDs with desirable characteristics, opening the door for facilitating the development of optoelectronics.

Plasma Processing and Treatment of 2D Transition Metal Dichalcogenides: Tuning Properties and Defect Engineering

“…743 Besides aforementioned substrate modifications, it has been recently shown that O 2 plasma pretreatment of Si or Si/SiO 2 substrates prior to CVD growth of TMD monolayers results in in situ etching of such layers during CVD processes. Zhang et al 755 found that by adjusting O 2 plasma pretreatment time and CVD parameters, it was possible to generate well-defined etch patterns with zigzag-terminated edges inside CVD-grown TMDs. The O 2 plasma pretreatment of the substrate substantially promoted the etching without altering the chemistry of TMD layers, such as by oxygen doping or oxidation.…”

Liquid metal catalyzed chemical vapor deposition towards morphology engineering of 2D epitaxial heterostructures

“…55 Consequently, the pursuit of morphology engineering through etching has garnered significant attention. 6,37,56,57 Notably, previous studies on the etching of 2D materials have been primarily limited to individual materials, with experimental investigations focusing on single cases and etching modes. Exploration of 2D heterostructures through etching is still in its nascent stages.…”

“…55 Consequently, the pursuit of morphology engineering through etching has garnered significant attention. 6,37,56,57…”

“…Since the successful peeling off of single-layer graphene in 2004, 1 the development of two-dimensional (2D) materials has captured significant attention due to their intriguing physical properties such as high carrier mobility, 2 mechanical strength, thermal conductivity, flexibility and transparency, chemical reactivity, and quantum hall effect. 3 Besides the most widely known graphene, researchers have also delved into the exploration of other 2D materials such as hexagonal boron nitride (hBN), 4 black phosphorus, 5 transition metal dichalcogenides (TMDs), 6 transition metal oxides, 7,8 and transition metal carbides or nitrides (MXenes), 9 with their conductivity ranging from insulators (s E 0) to conductors (s ranging from 0.1 S m À1 to 1000 S m À1 ). Besides, each of them exhibits unique functionalities, for instance, TMDs show the ability to transition from the direct bandgap to the indirect bandgap depending on the layer number, 10 and hBN shows the ability to screen charge trap sites to prevent scattering.…”

“…Besides, each of them exhibits unique functionalities, for instance, TMDs show the ability to transition from the direct bandgap to the indirect bandgap depending on the layer number, 10 and hBN shows the ability to screen charge trap sites to prevent scattering. 11 Consequently, the diverse properties of 2D materials enable a broad spectrum of applications in electronics, 6 optoelectronics, 12 spin electronics, 13 energy storage, 14 and biomedical treatments. 15,16 With the advancement of modern electronics, individual materials alone are unable to meet the diverse range of demands.…”