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Electronic properties of atomically thin MoS2 layers grown by physical vapour deposition: band structure and energy level alignment at layer/substrate interfaces

2018-02-16T16:29:20+00:00 February 16th, 2018|Categories: Publications|Tags: , |

RSC Adv., 2018, 8,7744-7752DOI: 10.1039/C8RA00635K, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Fabio Bussolotti, Jainwei Chai, Ming Yang, Hiroyo Kawai, Zheng Zhang, Shijie Wang, Swee Liang Wong, Carlos Manzano, Yuli Huang, Dongzhi Chi, Kuan Eng

Published in: "RSC Advances".

Hydrogen-assisted post-growth substitution of tellurium into molybdenum disulfide monolayers with tunable compositions

2018-02-16T10:30:36+00:00 February 16th, 2018|Categories: Publications|Tags: |

Herein we report the successful doping of tellurium (Te) into molybdenum disulfide (MoS 2 ) monolayers to form MoS 2 x Te 2(1− x ) alloy with variable compositions via a hydrogen-assisted post-growth chemical vapor deposition process. It is confirmed that H 2 plays an indispensable role in the Te substitution into as-grown MoS 2 monolayers. Atomic-resolution transmission electron microscopy allows us to determine the lattice sites and the concentration of introduced Te atoms. At a relatively low concentration, tellurium is only substituted in the sulfur sublattice to form monolayer MoS 2(1− x ) Te 2 x alloy, while with increasing Te concentration (up to ∼27.6% achieved in this study), local regions with enriched tellurium, large structural distortions, and obvious sulfur deficiency are observed. Statistical analysis of the Te distribution indicates the random substitution. Density function…

Published in: "Nanotechnology".

In Situ Repair of 2D Chalcogenides under Electron Beam Irradiation

2018-02-16T08:31:03+00:00 February 16th, 2018|Categories: Publications|Tags: , |

Abstract Molybdenum disulfide (MoS2) and bismuth telluride (Bi2Te3) are the two most common types of structures adopted by 2D chalcogenides. In view of their unique physical properties and structure, 2D chalcogenides have potential applications in various fields. However, the excellent properties of these 2D crystals depend critically on their crystal structures, where defects, cracks, holes, or even greater damage can be inevitably introduced during the preparation and transferring processes. Such defects adversely impact the performance of devices made from 2D chalcogenides and, hence, it is important to develop ways to intuitively and precisely repair these 2D crystals on the atomic scale, so as to realize high-reliability devices from these structures. Here, an in situ study of the repair of the nanopores in MoS2 and Bi2Te3 is carried out under electron beam irradiation by transmission electron microscopy. The experimental conditions allow visualization of the structural dynamics of MoS2 and Bi2Te3 crystals with unprecedented resolution. Real-time observation of the healing of defects at atomic resolution can potentially help to reproducibly fabricate and simultaneously image single-crystalline free-standing 2D chalcogenides. Thus, these findings demonstrate the viability of using an electron beam as an effective tool to precisely engineer materials to suit desired applications in the future. Controlled electron beam irradiation can be utilized as a tool to repair the nanopores in MoS2 and Bi2Te3 and lead to high-quality crystals with a low number of defects. The dynamic repair processes yield an in-depth understanding of the repair mechanism in 2D chalcogenides: the sites with more

Published in: "Advanced Materials".

Tuning the Electronic and Photonic Properties of Monolayer MoS2 via In Situ Rhenium Substitutional Doping

2018-02-16T08:28:40+00:00 February 16th, 2018|Categories: Publications|Tags: , , , |

Abstract Doping is a fundamental requirement for tuning and improving the properties of conventional semiconductors. Recent doping studies including niobium (Nb) doping of molybdenum disulfide (MoS2) and tungsten (W) doping of molybdenum diselenide (MoSe2) have suggested that substitutional doping may provide an efficient route to tune the doping type and suppress deep trap levels of 2D materials. To date, the impact of the doping on the structural, electronic, and photonic properties of in situ-doped monolayers remains unanswered due to challenges including strong film substrate charge transfer, and difficulty achieving doping concentrations greater than 0.3 at%. Here, in situ rhenium (Re) doping of synthetic monolayer MoS2 with ≈1 at% Re is demonstrated. To limit substrate film charge transfer, r-plane sapphire is used. Electronic measurements demonstrate that 1 at% Re doping achieves nearly degenerate n-type doping, which agrees with density functional theory calculations. Moreover, low-temperature photoluminescence indicates a significant quench of the defect-bound emission when Re is introduced, which is attributed to the MoO bond and sulfur vacancies passivation and reduction in gap states due to the presence of Re. The work presented here demonstrates that Re doping of MoS2 is a promising route toward electronic and photonic engineering of 2D materials. This work demonstrates in situ rhenium (Re) doping of synthetic monolayer MoS2 with ≈1 at% Re on r-plane sapphire. Electronic measurements elucidate that 1 at% Re doping achieves nearly degenerate n-type doping, which agrees with density functional theory calculations. Low-temperature photoluminescence measurements reveal suppression of defect emission induced by Re

Published in: "Advanced Functional Materials".

Mixed-solvent liquid exfoliated MoS2 NPs as peroxidase mimetics for colorimetric detection of H2O2 and glucose

2018-02-15T16:29:18+00:00 February 15th, 2018|Categories: Publications|Tags: |

RSC Adv., 2018, 8,7252-7259DOI: 10.1039/C7RA12584D, Paper Open Access &nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.Yuehua Zhao, Yu Huang, Jiangling Wu, Xiaoli Zhan, Yuanyang Xie, Dongyun Tang, Haiyan Cao, Wen YunUltra-small molybdenum disulfide nanoparticles (MoS2 NPs) prepared by

Published in: "RSC Advances".

Visual Immunoassays: Layered Aggregation with Steric Effect: Morphology-Homogeneous Semiconductor MoS2 as an Alternative 2D Probe for Visual Immunoassay (Small 7/2018)

2018-02-15T14:31:44+00:00 February 15th, 2018|Categories: Publications|Tags: |

In article number 1703560, Hong Qun Luo, Nian Bing Li, and co-workers develop a centrifugation-coupled strategy for size fractionation of exfoliated MoS2. Based on its unique semiconducting property and desired gel electrophoresis performance, layered MoS2 conjugated with antibodies, rivaled classic gold nanoparticles in a visual immunoassay. This study further reveals that 2D nanostructures could promote the development of next-generation visual sensing devices, especially in portable detection of tumor markers.

Published in: "Small".

Broad-spectrum enhanced absorption of graphene-molybdenum disulfide photovoltaic cells in metal-mirror microcavity

2018-02-15T14:31:08+00:00 February 15th, 2018|Categories: Publications|Tags: , |

The optical absorption of graphene-molybdenum disulfide photovoltaic cells (GM-PVc) in wedge-shaped metal-mirror microcavities (w-MMCs) combined with a spectrum-splitting structure was studied. Results showed that the combination of spectrum-splitting structure and w-MMC can enable the light absorption of GM-PVcs to reach about 65% in the broad spectrum. The influence of processing errors on the absorption of GM-PVcs in w-MMCs was 3–14 times lower than that of GM-PVcs in wedge photonic crystal microcavities. The light absorption of GM-PVcs reached 60% in the broad spectrum, even with the processing errors. The proposed structure is easy to implement and may have potentially important applications in the development of ultra-thin and high-efficiency solar cells and optoelectronic devices.

Published in: "Nanotechnology".

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