Layer-by-Layer Growth of AA-Stacking MoS₂ for Tunable Broadband Phototransistors

Abstract

The stacking configuration has been considered as an important additional degree of freedom to tune the physical property of layered materials, such as superconductivity and interlayer excitons. However, the facile growth of highly uniform stacking configuration is still a challenge. Herein, the AA-stacking MoS 2 domains with a ratio up to 99.5% has been grown by using the modified chemical vapor deposition through introducing NaCl molecules in the confined space. By tuning the growth time, MoS 2 domains would transit from an AA-stacking bilayer to an AAAAAstacking five-layer. The epitaxial growth mechanism has been insightfully studied, revealing that the critical nucleation size of the AA-stacking bilayer is 5.0 ± 3.0 μm. Through investigation of the photoluminescence, the photoemission, especially the indirect photoexcitation, is dependent on both the stacking fashion and layer number. Furthermore, by studying the gate-tuned MoS 2 phototransistors, we found a significant dependence on the stacking configuration of MoS 2 of the photoexcitation and a different gate tunable photoresponse. The AAA-stacking trilayer MoS 2 phototransistor delivers a photoresponse of 978.14 A W −1 at 550 nm. By correction of the external quantum efficiency with external field and illumination power density, it has been found that the photoresponse tunability is dependent on the layer number due to the strong photogating effect. This strategy provides a general avenue for the epitaxial growth of van der Waals film which will further facilitate the applications in a tunable photodetector.

Charge transport properties of SARS-CoV-2 Delta variant (B.1.617.2)

“…SARS-CoV-2 is a positive-sense single-stranded RNA virus of about 30000 base length. In recent years, some studies have studied the charge transport in nanomaterials [5] , [6] and the electrical properties of cytosine hydroxymethylated (Chm) DNA sequences [7] . A recent article found that single-molecule conductance techniques can be used to extract biologically relevant information from short RNA oligonucleotides by construct RNA:DNA hybrids [8] .…”

Highly Tunable, Broadband, and Negative Photoresponse MoS2 Photodetector Driven by Ion-Gel Gate Dielectrics

“…There are two typical vibration modes located at 384.69 and 404.18 cm –1 corresponding to the in-plane vibration mode (E 2g ) and out-of-plane vibration mode (A 1g ), respectively. The distance between the A 1g and E 2g is about 19.49 cm –1 , which further indicates its monolayer structure. , The typical photoluminescence band is located at about 668 nm. To fabricate the MoS 2 -based ion-gel phototransistor, the CVD-grown MoS 2 flake has been transferred to the precleaned sapphire substrate.…”

“…Therefore, the ion-gel does not obviously affect the electrical and photoelectrical properties of MoS 2 . The carrier mobility could be calculated by the equation , where C ox is the capacitance of the ion-gel membrane, L and W are the channel length and channel width, respectively, and I d and V d are separately the drain current and voltage. To estimate the C ox value of the ion-gel film, the frequency-dependent capacitance has been studied as shown in Figure S5, and the capacitance is about 10.5 μF/cm 2 at 0.1 Hz.…”

“…As shown in Figure a,b, the photoresponse R of the device is evaluated by where R is the photoresponse, I light and I dark are the current under illumination and in the dark, respectively. I photo is the photocurrent, P is the incident laser power density, and A is the device area.…”

NaCl-Assisted Temperature-Dependent Controllable Growth of Large-Area MoS2 Crystals Using Confined-Space CVD

“…Transition-metal dichalcogenides have gained a lot of popularity in recent years mainly because of the advantages they provide in terms of their usage in field-effect transistors (FETs), photodetectors, photodiodes, solar cells, and phototransistors . The layers of two-dimensional (2D) materials can be ultrathin, and the band gap can be tuned according to the thickness of the layers of the material from monolayer to multilayer. − MoS 2 is a very promising 2D material because of its outstanding performance in terms of carrier mobility, tunability of excitonic effects, and high current density of monolayer .…”