Query: Toward the Growth of High Mobility 2D Transition Metal Dichalcogenide Semiconductors

Candidate papers:

author_names: Henan Li

Jing-Kai Huang

Yumeng Shi

Lain-Jong Li
title: Toward the Growth of High Mobility 2D Transition Metal Dichalcogenide Semiconductors
venue: Advanced Materials Interfaces
year: 2019

abstract: We give here an overview on our results on the large area growth of 2D transition metal dichalcogenide semiconductors MoS<sub>2</sub> MoSe<sub>2</sub> WSe<sub>2</sub> using chemical vapor deposition. The growth of MoS<sub>2</sub> on sapphire occurs epitaxially with the crystalline orientation of the MoS<sub>2</sub> film closely matching that of the sapphire substrate, resulting in a high quality continuous film. The use of H<sub>2</sub>S results in more control over growth morphologies. WSe<sub>2</sub> and MoSe<sub>2</sub> have also been successfully grown using solid state precursors. Room temperature mobilities of all these materials exceed 10 cm<sup>2</sup>V<sup> 1</sup>s<sup> 1</sup> In contrast to MoS<sub>2</sub> WSe<sub>2</sub> and MoSe<sub>2</sub> show ambipolar behavior.
author_names: Dumitru Dumcenco

Dmitry Ovchinnikov

Kolyo Marinov

Andras Kis
title: High quality synthetic 2D transition metal dichalcogenide semiconductors
venue: 2016 46th European Solid State Device Research Conference (ESSDERC)
year: 2016

abstract: Transition metal dichalcogenides (TMDs) have previously been recognized as a new class of semiconducting 2D layered materials.1, 2 TMDs such as molybdenum disulfide (MoS2) and tungsten diselenide (WSe2) thus open up new opportunities in semiconductor technology for the development of future 2D electronics and optoelectronics. Furthermore, monolayer TMDs feature a direct energy band gap, good carrier mobility, and excellent 'on''off' current ratios when they are fabricated in field effect transistors. These are all advantageous properties for future low power electronic and optoelectronic devices. To achieve additional applications of these materials in advanced circuits, however, it is necessary to develop a 2D p n junction (i.e. the interface between a p type and an n type semiconductor) In earlier studies of such p n junctions, the focus has mainly been on vertically stacked van der Waals heterojunctions in which the interface properties and stacking angle strongly affect the junction performance.3, 4 Alternatively, it has been shown that chemical vapor deposition (CVD) can be used reliably for the growth of wafer scale 2D materials and is feasible for lateral heterojunction growth.5 The thermodynamically favored formation of TMD alloys at the hetero interface during the so called one pot synthetic process, however, remains an obstacle to the formation of lateral heterojunctions via direct CVD growth.6 8 Moreover, the one pot synthetic process only allows the growth of heterostructures with either different metals or different chalcogens, and this limits the materials that can be selected for practical applications.6 8 To provide a more reliable and robust growth method for 2D heterojunctions, we have therefore developed a new Figure 1. (a) Optical microscope image of the tungsten diselenide/ molybdenum disulfide (WSe2/MoS2) lateral heterojunction fabricated using the two step epitaxial growth method. (b) A high resolution scanning transmission electron microscope image of the heterojunction, showing the atomically sharp interface between the WSe2 and the MoS2.
author_names: Lain-Jong Li

Ming-Yang Li
title: Epitaxial growth of a 2D transition metal dichalcogenide lateral heterojunction
year: 2016

abstract: Two dimensional (2D) heterostructures based on layered transition metal dichalcogenides (TMDs) have attracted increasing attention for the applications of the next generation high performance integrated electronics and optoelectronics. Although various TMD heterostructures have been successfully fabricated, epitaxial growth of such atomically thin metal semiconductor heterostructures with a clean and sharp interface is still challenging. In addition, photodetectors based on such heterostructures have seldom been studied. Here, we report the synthesis of high quality vertical NbS2/MoS2 metallic semiconductor heterostructures. By using NbS2 as the contact electrodes, the field effect mobility and current on off ratio of MoS2 can be improved at least 6 fold and two orders of magnitude compared with the conventional Ti/Au contact, respectively. By using NbS2 as contact, the photodetector performance of MoS2 is much improved with higher responsivity and less response time. Such facile synthesis of atomically thin metal semiconductor heterostructures by a simple chemical vapor deposition strategy and its effectiveness as ultrathin 2D metal contact open the door for the future application of electronics and optoelectronics.
author_names: P Zhang

Ce Bian

Jiafu Ye

Ningyan Cheng

Xiao Wang

Huaning Jiang

Yi Wei

Yiwei Zhang

Yi Du

Lihong Bao

Weida Hu

Yongji Gong
title: Epitaxial growth of metal semiconductor van der Waals heterostructures NbS2/MoS2 with enhanced performance of transistors and photodetectors
venue: Science China Materials
year: 2020

abstract: Two dimensional (2D) layered semiconductors are emerging as promising candidates for next generation thin film electronics because of their high mobility, relatively large bandgap, low power switching, and the availability of large area growth methods. Thin film transistors (TFTs) based on multilayer transition metal dichalcogenides or black phosphorus offer unique opportunities for next generation electronic and optoelectronic devices. Here, we review recent progress in high mobility transistors based on multilayer 2D semiconductors. We describe the theoretical background on characterizing methods of TFT performance and material properties, followed by their applications in flexible, transparent, and optoelectronic devices. Finally, we highlight some of the methods used in metal semiconductor contacts, hybrid structures, heterostructures, and chemical doping to improve device performance.
author_names: Zhenxing Wang

Amber McCreary

Natalie Briggs

Joice Sophia Ponraj

Zai-Quan Xu

Sathish Chander Dhanabalan

Seong Yeoul
title: Recent progress in high mobility thin film transistors based on multilayer 2 D materials
year: 2017

abstract: Heterostructures based on two dimensional (2D) transition metal dichalcogenides semiconductors are reported to be promising building blocks for next generation integrated optoelectronic systems, owing to their atomic thin interface and interface induced properties. Previously reported works have mostly been directed to focus on the 2D/2D heterostructures, and their optoelectronic performance is still inferior to the expectations for practical applications, mainly attributed to their non ideal optical absorption when the thickness is confined at atomic scale. In this work, we have reported on high sensitivity photodetectors based on one dimensional (1D)/2D heterostructures consisting of CdS nanowire and WS2 nanosheets grown by direct chemical vapor deposition. The components of the heterostructures were confirmed by x ray diffraction, x ray photoelectron spectroscopy, transmission electron microscope, photoluminescence and Raman spectra measurements, confirming the high quality heterostructures. Photodetectors were then fabricated based on the as synthesized CdS/WS2 heterostructures, showing superior photodetection performances with a photoresponsivity of ~50 A W 1 and an ultrahigh photodetectivity of ~1012 Jones. Much higher responsivity of 5472 A W 1 and detectivity of 5 x 1013 Jones can be achieved through applying back gate voltage. The direct growth of such 1D/2D heterostructures may pave the way toward high performance integrated optoelectronics and systems.
author_names: Anlian Pan
title: Vapor growth of CdS nanowires/WS2 nanosheet heterostructures with sensitive photodetections.
venue: Nanotechnology
year: 2019

abstract: Two dimensional (2D) nanosheets of layered transition metal dichalcogenides (TMDs) have received significant attention because some of them are semiconductors with sizable band gaps and are naturally abundant. Here, we report the photolithographic pattern transfer (PPT) technology used to fabricate FETs of two dimensional materials. To explore the electrical properties and realize functional optoelectronics and electronics from semiconductors, the fabrication of devices (such as field effect transistors (FET) diodes and Hall bars) and integrated circuits is necessary and important. An essential step in fabricating micro /nanoelectronics is making the metal electrode arrays. Such a PPT method can be used to efficiently design and prepare complicated electrode arrays for electronics and optoelectronics, and is especially suitable for 2D materials. Few layer MoS 2 made by electron beam lithography (EBL) gold wire mask moving (GWM) and this method are used as templates for comparison. The mobility of our thin MoS 2 flake is comparable to the results of devices from EBL and better than the results of the GWM method. Further complicated device applications such as a top gate FET, a Hall bar, and heterostructure transistors could also be easily realized based on such a method. We also report the growth and electric transport of Co doped MoS 2 bilayer. As the initial loading of the sulfur increases, the morphology of the Co x Mo 1 x S 2 (0 x <1) nanosheets becomes hexagons from David stars step by step at 680degC. We find that Co atoms mainly distribute at the edge of nanosheets. When the temperature increases from 680 to 750degC, high quality cubic pyrite type crystal structure CoS 2 grows on the surface of Co x Mo 1 x S 2 nanosheet gradually and forms hexagonal film induced by the nanosheet. Electrical transport measurements reveal that the Co x Mo 1 x S 2 nanosheets and CoS 2 films exhibit n type semiconducting transport behavior and half metallic behavior, respectively. Theoretical calculations of their band structures agree well with the experimental results. These alloy nanosheets of Co x Mo 1 x S 2 should have large potential applications in the tunable optoelectronics. Then, we report the vapor phase growth and optoelectronic property of vertical bilayer SnS 2 /MoS 2 heterostructure. 2D van der Waals heterostructures with different types of band alignment have recently attracted great attention due to their unique optical and electrical properties. Most 2D heterostructures are formed by transfer stacking two monolayers together, but the interfacial quality and controllable orientation of such artificial structures are inferior to those epitaxial grown heterostructures. An extremely Type II band alignment exists in this 2D heterostructure, with band offset larger than any other reported. Consistent with the large band offset, distinctive optical properties including strong photoluminescence quenching in the heterostructure area are observed in the heterostructure. The SnS 2 /MoS 2 heterostructures also exhibit well aligned lattice orientation between the two layers, forming a periodic Moire superlattice pattern with high lattice mismatch. Electrical transport and photoresponsive studies demonstrate that the SnS 2 /MoS 2 heterostructures exhibit an obvious photovoltaic effect and possess high on/off ratio >10 6 high mobility (27.6 cm 2 V 1 s 1 and high photoresponsivity (1.36 A W 1 Efficient synthesis of such vertical heterostructure may open up new realms in 2D functional electronics and optoelectronics. Finally we give some perspectives on studies of two dimensional materials in future.
author_names: Bo Li

Zhongming Wei
title: Growth and optoelectronic property of two dimensional semiconductors
year: 2017

abstract: Significance Traditional semiconductor fabrication methods, such as lithography and etching, have been sufficient for the needs of integrated circuits over past decades. Their applicability has also been demonstrated in emerging 2D materials, which offers facile processing over large lateral dimensions, while unique and remarkable properties due to the confinement within atomic thicknesses. Nevertheless, each fabrication step adds cost to the manufacturing and increases the possibility of quality degradation. Here, we developed a method to directly synthesize arbitrary monolayer molybdenum disulfide patterns with high spatial resolution, excellent homogeneity, and electrical performance on insulating SiO2/Si. Significantly, our on demand method allows for the repeated growth of patterned 2D materials with preserved structural integrity and material qualities, paving the way for simpler and cost effective fabrication. The 2D van der Waals crystals have shown great promise as potential future electronic materials due to their atomically thin and smooth nature, highly tailorable electronic structure, and mass production compatibility through chemical synthesis. Electronic devices, such as field effect transistors (FETs) from these materials require patterning and fabrication into desired structures. Specifically, the scale up and future development of "2D" based electronics will inevitably require large numbers of fabrication steps in the patterning of 2D semiconductors, such as transition metal dichalcogenides (TMDs) This is currently carried out via multiple steps of lithography, etching, and transfer. As 2D devices become more complex (e.g. numerous 2D materials, more layers, specific shapes, etc. the patterning steps can become economically costly and time consuming. Here, we developed a method to directly synthesize a 2D semiconductor, monolayer molybdenum disulfide (MoS2) in arbitrary patterns on insulating SiO2/Si via seed promoted chemical vapor deposition (CVD) and substrate engineering. This method shows the potential of using the prepatterned substrates as a master template for the repeated growth of monolayer MoS2 patterns. Our technique currently produces arbitrary monolayer MoS2 patterns at a spatial resolution of 2 mm with excellent homogeneity and transistor performance (room temperature electron mobility of 30 cm2 V 1 s 1 and on off current ratio of 107) Extending this patterning method to other 2D materials can provide a facile method for the repeatable direct synthesis of 2D materials for future electronics and optoelectronics.
author_names: Yunfan Guo

Pin-Chun Shen

Cong Su

Ang-Yu Lu

Marek Hempel

Yimo Han

Qingqing Ji

Yuxuan Lin

Enzheng Shi

Elaine McVay

Letian Dou

David A Muller

Tomas Palacios

Ju Li

Xi Ling

Jing Kong
title: Additive manufacturing of patterned 2D semiconductor through recyclable masked growth
venue: Proceedings of the National Academy of Sciences
year: 2019

abstract: Chemical vapor deposition (CVD) is a powerful method employed for high quality monolayer crystal growth of 2D transition metal dichalcogenides with much effort invested toward improving the growth process. Here, we report a novel method for CVD based growth of monolayer molybdenum disulfide (MoS2) by using thermally evaporated thin films of molybdenum trioxide (MoO3) as the molybdenum (Mo) source for coevaporation. Uniform evaporation rate of MoO3 thin films provides uniform Mo vapors which promote highly reproducible single crystal growth of MoS2 throughout the substrate. These high quality crystals are as large as 95 mm and are characterized by scanning electron microscopy, Raman spectroscopy, photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy. The bottom gated field effect transistors fabricated using the as grown single crystals show n type transistor behavior with a good on/off ratio of 106 under ambient conditions. Our results presented here address the precursor vapor control during the CVD process and is a major step forward toward reproducible growth of MoS2 for future semiconductor device applications.
author_names: Sajeevi Sankalpani Withanage

Hirokjyoti Kalita

Hee-Suk Chung

Tania Roy

Yeonwoong Jung

Saiful I Khondaker
title: Uniform Vapor Pressure Based Chemical Vapor Deposition Growth of MoS2 Using MoO3 Thin Film as a Precursor for Coevaporation
venue: ACS omega
year: 2018

abstract: We present a DC AC Hall effect analysis on transition metal dichalcogenides comprising natural crystals of molybdenum disulfide and tungsten diselenide; and synthetic crystals of hafnium diselenide, molybdenum ditelluride, molybdenum diselenide and niobium doped molybdenum disulfide. We observe a wide range of Hall mobility and carrier concentration values with either a net electron or hole carrier type. The synthetic niobium doped molybdenum disulfide crystal exhibits a net hole carrier type and a carrier concentration approximately two orders of magnitude higher than a non intentionally doped natural molybdenum disulfide crystal, with an equivalent reduction in Hall mobility. This synthetic niobium doped molybdenum disulfide crystal also shows a significantly reduced resistivity when compared to the other crystals. Secondary ion mass spectrometry shows higher counts of niobium in the intentionally doped synthetic niobium molybdenum disulfide crystal, in addition to various other high contamination counts in both the natural and synthetic molybdenum disulfide crystals, correlating well with the significant range of high resistivity observed. Compared to silicon, the resistivity in these contaminated TMD materials reduces less rapidly with increasing equivalent carrier concentration levels, and the resistivity is higher in magnitude by a factor of approximately 4 10 when compared to silicon, which in turn reduces the achievable Hall mobility by at least a similar factor. It is therefore suggested that more controlled growth methods of TMD materials which lead to significantly reduced contamination elements and levels, with improved stoichiometry, could potentially provide a significant increase in Hall mobility assuming no change in carrier properties.
author_names: Scott Monaghan

Farzan Gity

Ray Duffy

Gioele Mirabelli

Melissa M McCarthy

Karim Cherkaoui

Ian M Povey

Roger Nagle

Paul K Hurley

Jeffrey R Lindemuth

Enrico Napolitani
title: Hall effect mobility for a selection of natural and synthetic 2D semiconductor crystals
venue: 2017 Joint International EUROSOI Workshop and International Conference on Ultimate Integration on Silicon (EUROSOI ULIS)
year: 2017