scholarly journals Methane-Mediated Vapor Transport Growth of Monolayer WSe2 Crystals

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1642
Author(s):  
Hyeon-Sik Jang ◽  
Jae-Young Lim ◽  
Seog-Gyun Kang ◽  
Sang-Hwa Hyun ◽  
Sana Sandhu ◽  
...  

The electrical and optical properties of semiconducting transition metal dichalcogenides (TMDs) can be tuned by controlling their composition and the number of layers they have. Among various TMDs, the monolayer WSe2 has a direct bandgap of 1.65 eV and exhibits p-type or bipolar behavior, depending on the type of contact metal. Despite these promising properties, a lack of efficient large-area production methods for high-quality, uniform WSe2 hinders its practical device applications. Various methods have been investigated for the synthesis of large-area monolayer WSe2, but the difficulty of precisely controlling solid-state TMD precursors (WO3, MoO3, Se, and S powders) is a major obstacle to the synthesis of uniform TMD layers. In this work, we outline our success in growing large-area, high-quality, monolayered WSe2 by utilizing methane (CH4) gas with precisely controlled pressure as a promoter. When compared to the catalytic growth of monolayered WSe2 without a gas-phase promoter, the catalytic growth of the monolayered WSe2 with a CH4 promoter reduced the nucleation density to 1/1000 and increased the grain size of monolayer WSe2 up to 100 μm. The significant improvement in the optical properties of the resulting WSe2 indicates that CH4 is a suitable candidate as a promoter for the synthesis of TMD materials, because it allows accurate gas control.

Nanoscale ◽  
2021 ◽  
Author(s):  
Darren Nutting ◽  
Gabriela Augusta Prando ◽  
Marion Severijnen ◽  
Ingrid Barcelos ◽  
Shi Guo ◽  
...  

Advanced van der Waals (vdW) heterostructure devices rely on the incorporation of high quality dielectric materials which need to possess a low defect density as well as being atomically smooth...


Nanoscale ◽  
2021 ◽  
Author(s):  
Anh Tuan Hoang ◽  
Kairui Qu ◽  
Xiang Chen ◽  
Jong-Hyun Ahn

This article reviews the latest advances in the synthesis of wafer-scale thin films using chemical vapor deposition and solution-based methods and various device applications.


Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7340
Author(s):  
Yoonsok Kim ◽  
Taeyoung Kim ◽  
Eun Kyu Kim

Two-dimensional (2D) materials, such as molybdenum disulfide (MoS2) of the transition metal dichalcogenides family, are widely investigated because of their outstanding electrical and optical properties. However, not much of the 2D materials research completed to date has covered large-area structures comprised of high-quality heterojunction diodes. We fabricated a large-area n-MoS2/p-Si heterojunction structure by sulfurization of MoOx film, which is thermally evaporated on p-type silicon substrate. The n-MoS2/p-Si structure possessed excellent diode characteristics such as ideality factor of 1.53 and rectification ratio in excess of 104. Photoresponsivity and detectivity of the diode showed up to 475 mA/W and 6.5 × 1011 Jones, respectively, in wavelength ranges from visible to near-infrared. The device appeared also the maximum external quantum efficiency of 72%. The rise and decay times of optical transient response were measured about 19.78 ms and 0.99 ms, respectively. These results suggest that the sulfurization process for large-area 2D heterojunction with MoS2 can be applicable to next-generation electronic and optoelectronic devices.


2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Mohamed A. Basyooni ◽  
Shrouk E. Zaki ◽  
Mohamed Shaban ◽  
Yasin Ramazan Eker ◽  
Mucahit Yilmaz

Abstract The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.


RSC Advances ◽  
2017 ◽  
Vol 7 (43) ◽  
pp. 26665-26672 ◽  
Author(s):  
Chao Zhao ◽  
Tien Khee Ng ◽  
Chien-Chih Tseng ◽  
Jun Li ◽  
Yumeng Shi ◽  
...  

High-quality nitride nanowires on large-area layered transition metal dichalcogenides are first reported, which yielded light-emitting diodes (LEDs) with superior performance.


Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1994
Author(s):  
Han Li ◽  
Yating Ma ◽  
Zhongjie Xu ◽  
Xiang’ai Cheng ◽  
Tian Jiang

Fundamental researches and explorations based on transition metal dichalcogenides (TMDCs) mainly focus on their monolayer counterparts, where optical densities are limited owing to the atomic monolayer thickness. Photoluminescence (PL) yield in bilayer TMDCs is much suppressed owing to indirect-bandgap properties. Here, optical properties are explored in artificially twisted bilayers of molybdenum disulfide (MoS2). Anomalous interlayer coupling and resultant giant PL enhancement are firstly observed in MoS2 bilayers, related to the suspension of the top layer material and independent of twisted angle. Moreover, carrier dynamics in MoS2 bilayers with anomalous interlayer coupling are revealed with pump-probe measurements, and the secondary rising behavior in pump-probe signal of B-exciton resonance, originating from valley depolarization of A-exciton, is firstly reported and discussed in this work. These results lay the groundwork for future advancement and applications beyond TMDCs monolayers.


2021 ◽  
Vol 23 (10) ◽  
pp. 6298-6308
Author(s):  
Chan Gao ◽  
Xiaoyong Yang ◽  
Ming Jiang ◽  
Lixin Chen ◽  
Zhiwen Chen ◽  
...  

The combination of defect engineering and strain engineering for the modulation of the mechanical, electronic and optical properties of monolayer transition metal dichalcogenides (TMDs).


2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Caihong Li ◽  
Juntong Zhu ◽  
Wen Du ◽  
Yixuan Huang ◽  
Hao Xu ◽  
...  

AbstractMonolayer transition metal dichalcogenides (TMDs) show promising potential for next-generation optoelectronics due to excellent light capturing and photodetection capabilities. Photodetectors, as important components of sensing, imaging and communication systems, are able to perceive and convert optical signals to electrical signals. Herein, the large-area and high-quality lateral monolayer MoS2/WS2 heterojunctions were synthesized via the one-step liquid-phase chemical vapor deposition approach. Systematic characterization measurements have verified good uniformity and sharp interfaces of the channel materials. As a result, the photodetectors enhanced by the photogating effect can deliver competitive performance, including responsivity of ~ 567.6 A/W and detectivity of ~ 7.17 × 1011 Jones. In addition, the 1/f noise obtained from the current power spectrum is not conductive to the development of photodetectors, which is considered as originating from charge carrier trapping/detrapping. Therefore, this work may contribute to efficient optoelectronic devices based on lateral monolayer TMD heterostructures.


Author(s):  
Yan Liu ◽  
Qiang Zhou ◽  
Yalan Yan ◽  
Liang Li ◽  
Jian Zhu ◽  
...  

Pressure has been considered as an effective technique to modulate the structural, electronic, and optical properties of transition metal dichalcogenides (TMDs) materials. Here, by performing in situ high pressure Raman,...


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