Direct Patterning of Optoelectronic Nanostructures Using Encapsulated Layered Transition Metal Dichalcogenides

Abstract

Direct top-down nanopatterning of semiconductors is a powerful tool for engineering properties of optoelectronic devices. Translating this approach to two-dimensional semiconductors such as monolayer transition metal dichalcogenides (TMDs) is challenging because of both the small scales required for confinement and the degradation of electronic and optical properties caused by high-energy and high-dose electron radiation used for high-resolution top-down direct electron beam patterning. We show that encapsulating a TMD monolayer with hexagonal boron nitride preserves the narrow exciton linewidths and emission intensity typical in such heterostructures after electron beam lithography, allowing direct patterning of functional optical monolayer nanostructures on scales of a few tens of nanometers. We leverage this fabrication method to study size-dependent effects on nanodot arrays of MoS2 and MoSe2 as well as laterally confined electrical transport devices, demonstrating the potential of top-down lithography for nanoscale TMD optoelectronics.

Heteroatoms (Si, B, N, and P) doped 2D monolayer MoS2for NH3gas detection

“…8 Though it is a challenging task to achieve gas sensing under extreme environmental conditions, molybdenum disulfide (MoS 2 ), as a typical transition metal with its characteristic of higher charge carrier mobility, has offered us a great opportunity to surmount these challenges to some extent. 9,10…”

“…8 Though it is a challenging task to achieve gas sensing under extreme environmental conditions, molybdenum disulde (MoS 2 ), as a typical transition metal with its characteristic of higher charge carrier mobility, has offered us a great opportunity to surmount these challenges to some extent. 9,10 In line with the development of experimental strategies, density functional theory (DFT) has recently been used by many scientists employing theoretical calculations to predict and understand the mechanistic behaviour, sensitivity and conductivity of the gas sensing ability of many materials. Enhancing the response of NH 3 graphene-sensors by using devices with different graphene-substrate distances was conducted by Cadore A. R. et al 11 and their results show that graphene-ammonia gas sensors based on a G/hBN heterostructure exhibit the fastest recovery times for NH 3 exposure and are only slightly affected by wet or dry air environments.…”

Tunable Emission from Localized Excitons Deterministically Positioned in Monolayer p–n Junctions

“…Next, the gates are capped with a multilayer flake of hexagonal boron nitride (h-BN), transferred via polymer-based methods, , which serves as the gate dielectric. h-BN was chosen here due to its stable performance in contrast to metal oxides as well as its robustness to electron beam irradiation. , A layer of PMMA is then spin-coated over the device and irradiated at a spot between the gates by an electron beam. With a dosage of 64 mC/cm 2 , a dielectric nanopillar of height 150–200 nm (depending on the PMMA solution concentration and spin speed) remains after the rest of the resist is washed away with solvents .…”

Heterostructure-Based Optoelectronic Neuromorphic Devices

“…Meanwhile, heterostructure (i.e., heterojunction) refers to the interface between two different material layers, in which these materials have different energy band structures, and accordingly, energy bandgaps [41][42][43]. With respect to the optoelectronic property aspect, due to the disparate energy band junction, an additional photoelectric effect or photogating effect can be obtained by means of the energy band alignment structure [44][45][46][47][48][49]. Thus, the benefits of heterostructures include an improved photo-response resulting from the junction structure with energy band differences, a versatility that allows application in various scenarios based on different combinations, and the ability to explore expandable or controllable wavelength ranges depending on the combination of the chosen materials.…”