Query: Chemical vapor deposition of layered two-dimensional MoSi2N4 materials

Candidate papers:

abstract: Stabilizing monolayer nitrides with silicon Transition metal carbides and nitrides are nonlayered materials that in monolayer form have potentially useful electronic and chemical properties. These monolayers are usually made by chemical etching that produces flakes with surface defects that have poor air and water stability. Hong et al. report that introducing silicon during chemical vapor deposition growth of molybdenum nitride passivates the surface and prevents island formation. Centimeter scale monolayer films of the semiconductor MoSi2N4 form as a MoN2 layer sandwiched by two Si N bilayers. These layers possess high mechanical strength and ambient stability. Science, this issue p. 670 Addition of silicon during film growth stabilized a molybdenum nitride monolayer by sandwiching it between two Si N bilayers. Identifying two dimensional layered materials in the monolayer limit has led to discoveries of numerous new phenomena and unusual properties. We introduced elemental silicon during chemical vapor deposition growth of nonlayered molybdenum nitride to passivate its surface, which enabled the growth of centimeter scale monolayer films of MoSi2N4. This monolayer was built up by septuple atomic layers of N Si N Mo N Si N, which can be viewed as a MoN2 layer sandwiched between two Si N bilayers. This material exhibited semiconducting behavior (bandgap ~1.94 electron volts) high strength ~66 gigapascals) and excellent ambient stability. Density functional theory calculations predict a large family of such monolayer structured two dimensional layered materials, including semiconductors, metals, and magnetic half metals.
author_names: Yi-Lun Hong

Zhibo Liu

Lingqian Wang

Tianya Zhou

Wei Ma

Chuan Xu

Shun Feng

Long Chen

Maolin Chen

Dongming Sun

Xing-Qiu Chen

Hui-Ming Cheng

Wencai Ren
title: Chemical vapor deposition of layered two dimensional MoSi2N4 materials
venue: Science
year: 2020

abstract: Two dimensional (2D) materials with atomic thickness are promising candidates for the applications in future semiconductor devices, owing to their fascinating physical properties and superlative optoelectronic performance. Chemical vapor deposition (CVD) is considered to be an efficient method for large scale preparation of 2D materials toward practical applications. However, the high melting points of metal precursors and the thermodynamics instabilities of metastable phases limit the direct CVD synthesis of plenty of 2D materials. The salt has recently been introduced into the CVD process, which proved to be effective to address these issues. In this review, we highlighted the latest progress in the salt assisted CVD growth of 2D materials, including layered and non layered crystals. Firstly, strategies of adding salts are summarized. Then, the salt assisted growth of various layered materials is presented, emphasizing on the transition metal chalcogenides of stable and metastable phases. Furthermore, strategies to grow ultrathin non layered materials are discussed. We provide viewpoints into the techniques of using salt, the effects of salt, and the growth mechanisms of 2D crystals. Finally, we offer the challenges to be overcome and further research directions of this emerging salt assisted CVD technique.
author_names: Wei Han

Kailang Liu

Sanjun Yang

Fakun Wang

Jianwei Su

Bao Jin

Huiqiao Li

Tianyou Zhai
title: Salt assisted chemical vapor deposition of two dimensional materials
venue: Science China Chemistry
year: 2019

abstract: Quasi one dimensional (1D)/two dimensional (2D) ZrTe3 attracts intense interest as a typical charge density wave (CDW) bearing material. However, the conventional chemical vapor transport (CVT) synthesis of bulk ZrTe3 is limited by high time consumption, even up to weeks, and low morphological controllability, so it is highly desirable to develop feasible methods for fast and controlled ZrTe3 growth, and so far, these have not been demonstrated. In this work, we first demonstrated that ZrTe3 nanoribbons can be grown directly by a modified chemical vapor deposition (CVD) method. The growth time is significantly reduced to less than 90 min, and the size of ZrTe3 nanoribbons can be well tuned by controlling the growth time and growth temperature. Moreover, differing from most of the other transition metal trichalcogenides (TMTCs) we reveal that ZrTe3 nanoribbons exhibit both competing and synergistic magnetic properties originating from their intrinsic diamagnetism and unexpected ferromagnetism, which can be attributed to their structural imperfection and edge states due to the reduced dimensionality. Such observable ferromagnetism might favor the exploration of their spin electronic applications.
author_names: Xuegang Yu

Xiaokun Wen

Wenfeng Zhang

Li Yang

Hao Wu

Xun Lou

Zijian Xie

Yuan Liu

Haixin Chang
title: Fast and controlled growth of two dimensional layered ZrTe3 nanoribbons by chemical vapor deposition
year: 2019

abstract: Chemical vapor deposition (CVD) route has emerged as an effective method for the successful synthesis of two dimensional (2D) materials with satisfactory crystal quality, especially for the synthesis of wafer scale, uniform thickness or large domain size single crystal transition metal chalcogenides (TMCs) To achieve this, the salt assisted CVD strategy has been proved to be powerful to reduce the high melting point of the metal related precursor, decrease the nucleation density and increase the reaction rate on the solid template. However, the specific roles of alkali metals and halide components still remain unclear. Herein, the functions of salts in the growth of TMCs have been discussed by summarizing some recent achievements in salt assisted synthesis results, wherein salts are mainly introduced as additives in metal precursors to achieve the wafer scale uniform growth of monolayer and thickness tunable multi layered TMCs, and for serving as 3D templates (especially NaCl) to realize the scalable production of TMCs. Moreover, the existing challenges and viable future directions are also proposed for in depth understanding of salt assisted C4VD methods and for exploring more efficient CVD strategies.
author_names: Chunyu Xie

Pengfei Yang

Yahuan Huan

Fangfang Cui

Yanfeng Zhang
title: Roles of salts in the chemical vapor deposition synthesis of two dimensional transition metal chalcogenides.
venue: Dalton transactions
year: 2020

abstract: Two dimensional semiconducting transition metal dichalcogenides embedded in optical microcavities in the strong exciton photon coupling regime may lead to promising applications in spin and valley addressable polaritonic logic gates and circuits. One significant obstacle for their realization is the inherent lack of scalability associated with the mechanical exfoliation commonly used for fabrication of two dimensional materials and their heterostructures. Chemical vapor deposition offers an alternative scalable fabrication method for both monolayer semiconductors and other two dimensional materials, such as hexagonal boron nitride. Observation of the strong light matter coupling in chemical vapor grown transition metal dichalcogenides has been demonstrated so far in a handful of experiments with monolayer molybdenum disulfide and tungsten disulfide. Here we instead demonstrate the strong exciton photon coupling in microcavities comprising large area transition metal dichalcogenide hexagonal boron nitride heterostructures made from chemical vapor deposition grown molybdenum diselenide and tungsten diselenide encapsulated on one or both sides in continuous few layer boron nitride films also grown by chemical vapor deposition. These transition metal dichalcogenide hexagonal boron nitride heterostructures show high optical quality comparable with mechanically exfoliated samples, allowing operation in the strong coupling regime in a wide range of temperatures down to 4 Kelvin in tunable and monolithic microcavities, and demonstrating the possibility to successfully develop large area transition metal dichalcogenide based polariton devices.
author_names: Daniel Gillard

Armando Genco

Seongjoon Ahn

T P Lyons

Kyung Yeol Ma

A-Rang Jang

Toby Severs Millard

Aurelien A P Trichet

Rahul Jayaprakash

Kyriacos Georgiou

David G Lidzey

Jason M Smith

Hyeon Suk Shin

Alexander I Tartakovskii
title: Strong exciton photon coupling in large area MoSe2 and WSe2 heterostructures fabricated from two dimensional materials grown by chemical vapor deposition
year: 2020

abstract: The insulator Na2Ta4O11 has been considered as a potential photocatalyst. However, little attention has been given to the synthesis of Na2Ta4O11 nanoparticles, let alone the growth of two dimensional (2D) layered Na2Ta4O11 flake, which may bring innovative properties and promising applications. Here, the 2D thin layer Na2Ta4O11 flake was first produced by chemical vapor deposition (CVD) method, with the smallest thickness reported currently. We have also synthesized 2D Na2Ta4O11 flake over 100 mm, which was the largest value over the 2D level reported to date. Our work proposed novel strategies to synthesize other 2D metal oxide material and endow the Na2Ta4O11 more properties and applications.
author_names: Yuanyuan Jin

Huimin Li

Song Liu
title: Growth of large scale two dimensional insulator Na2Ta4O11 through chemical vapor deposition
year: 2020

abstract: ConspectusSince the rise of two dimensional (2D) materials, synthetic methods including mechanical exfoliation, solution synthesis, and chemical vapor deposition (CVD) have been developed. Mechanical exfoliation prepares randomly shaped materials with small size. Solution synthesis introduces impurities that degrade the performances. CVD is the most successful one for low cost scalable preparation. However, when it comes to practical applications, disadvantages such as high operating temperature ~1000 degC) probable usage of metal catalysts, contamination, defects, and interstices introduced by postgrowth transfer are not negligible. These are the reasons why plasma enhanced CVD (PECVD) a method that enables catalyst free in situ preparation at low temperature, is imperatively desirable.In this Account, we summarize our recent progress on controllable preparation of 2D materials by PECVD and their applications. We found that there was a competition between etching and nucleation and deposition in PECVD, making it highly controllable to obtain desired materials. Under different equilibrium states of the competition, various 2D materials with diverse morphologies and properties were prepared including pristine or nitrogen doped graphene crystals, graphene quantum dots, graphene nanowalls, hexagonal boron nitride (h BN) B C N ternary materials (BCxN) etc. We also used mild plasma to modify or treat 2D materials (e.g. WSe2) for desired properties.PECVD has advantages such as low temperature, transfer free process, and industrial compatibility, which enable facile, scalable, and low cost preparation of 2D materials with clean surfaces and interfaces directly on noncatalytic substrates. These merits significantly benefit the as prepared materials in the applications. Field effect transistors with high motilities were directly fabricated on graphene and nitrogen doped graphene. By use of h BN as the dielectric interfacial layer, both mobilities and saturated power densities of the devices were improved owing to the clean, closely contacted interface and enhanced interfacial thermal dissipation. High quality materials and interfaces also enabled promising applications of these materials in photodetectors, pressure sensors, biochemical sensors, electronic skins, Raman enhancement, etc. To demonstrate the commercial applications, several prototypical devices were studied such as distributed pressure sensor arrays, touching module on a robot hand for braille recognition, and smart gloves for recording sign language. Finally, we discuss opportunities and challenges of PECVD as a comprehensive preparation methodology of 2D materials for future applications beyond traditional CVD.
author_names: Kongyang Yi

Donghua Liu

Xiaosong Chen

Jun Yang

Dapeng Wei

Yunqi Liu

Dacheng Wei
title: Plasma Enhanced Chemical Vapor Deposition of Two Dimensional Materials for Applications.
venue: Accounts of chemical research
year: 2021

abstract: The discovery of ferromagnetic two dimensional van der Waals materials has opened up opportunities to explore intriguing physics and to develop innovative spintronic devices. However, controllable synthesis of these 2D ferromagnets and enhancing their stability under ambient conditions remain challenging. Here, we report chemical vapor deposition growth of air stable 2D metallic 1T CrTe2 ultrathin crystals with controlled thickness. Their long range ferromagnetic ordering is confirmed by a robust anomalous Hall effect, which has seldom been observed in other layered 2D materials grown by chemical vapor deposition. With reducing the thickness of 1T CrTe2 from tens of nanometers to several nanometers, the easy axis changes from in plane to out of plane. Monotonic increase of Curie temperature with the thickness decreasing from ~130.0 to ~7.6 nm is observed. Theoretical calculations indicate that the weakening of the Coulomb screening in the two dimensional limit plays a crucial role in the change of magnetic properties.
author_names: Lingjia Meng

Zhang Zhou

Mingquan Xu

Shiqi Yang

Kunpeng Si

Lixuan Liu

Xingguo Wang

Huaning Jiang

Bixuan Li

Peixin Qin

Peng Zhang

Jinliang Wang

Zhiqi Liu

Peizhe Tang

Yu Ye

Wu Zhou

Lihong Bao

Hongquing Gao

Yongji Gong
title: Anomalous thickness dependence of Curie temperature in air stable two dimensional ferromagnetic 1T CrTe2 grown by chemical vapor deposition
venue: Nature communications
year: 2021

abstract: Two dimensional (2D) palladium diselenide (PdSe2 has strong interlayer coupling and a puckered pentagonal structure, leading to remarkable layer dependent electronic structures and highly anisotropic in plane optical and electronic properties. However, the lack of high quality, 2D PdSe2 crystals grown by bottom up approaches limits the study of their exotic properties and practical applications. In this work, chemical vapor deposition growth of highly crystalline few layer =2 layers) PdSe2 crystals on various substrates is reported. The high quality of the PdSe2 crystals is confirmed by low frequency Raman spectroscopy, scanning transmission electron microscopy, and electrical characterization. In addition, strong in plane optical anisotropy is demonstrated via polarized Raman spectroscopy and second harmonic generation maps of the PdSe2 flakes. A theoretical model based on kinetic Wulff construction theory and density functional theory calculations is developed and described the observed evolution of "square like" shaped PdSe2 crystals into rhombus due to the higher nucleation barriers for stable attachment on the (1,1) and (1, 1) edges, which results in their slower growth rates. Few layer PdSe2 field effect transistors reveal tunable ambipolar charge carrier conduction with an electron mobility up to 294 cm2 V 1 s 1 which is comparable to that of exfoliated PdSe2 indicating the promise of this anisotropic 2D material for electronics.
author_names: Yiyi Gu

Hui Cai

Jichen Dong

Yiling Yu

Anna N Hoffman

Chenze Liu

Akinola D Oyedele

Yu-Chuan Lin

Zhuozhi Ge

Alexander A Puretzky

Gerd Duscher

Matthew F Chisholm

Philip D Rack

Christopher M Rouleau

Zheng Gai

Xiangmin Meng

Feng Ding

David B Geohegan

Kai Xiao
title: Two Dimensional Palladium Diselenide with Strong In Plane Optical Anisotropy and High Mobility Grown by Chemical Vapor Deposition.
venue: Advanced materials
year: 2020

abstract: Due to the confinement of the charge, spin, and heat transport in the plane, graphene and related two dimensional (2D) materials have been demonstrated to own many unique and excellent properties and witnessed many breakthroughs in physics. They show great application potential in many fields, especially for electronics and optoelectronics. However, a bottleneck to widespread applications is precise and reliable fabrication, in which the control of the layer number and domain assembly is the most basic and important since they directly determine the qualities and properties of 2D materials. The chemical vapor deposition (CVD) strategy was regarded as the frontrunner to achieve this target, and the design of the catalytic substrate is of great significance since it has the most direct influence on the catalysis and mass transfer, which can be the most essential elemental steps. In recent years, as compared to traditional solid metal catalysts, the emergence of liquid metal catalysts has brought a brand new perspective and contributes to a huge change and optimization in the fabrication of 2D materials. On one hand, strictly self limited growth behavior is discovered and is robust to the variation of the growth parameters. The atoms in the liquid metal tend to move intensely and arrange in an amorphous and isotropic way. The liquid surface is smooth and isotropic, and the vacancies in the fluidic liquid phase enable the embedding of heteroatoms. The phase transition from liquid to solid will facilitate the unique control of the mass transfer path, which can trigger new growth mechanisms. On the other hand, the excellent rheological properties of liquid metals allow us to explore self assembly of the 2D materials grown on the surface, which can activate new applications based on the derived collective properties, such as the integrated devices. Indeed, liquid metals show many unique behaviors in the catalytic growth and assembly of 2D materials. Thus, this Account aims to highlight the controllable fabrication of graphene and related 2D materials on liquid metals. By utilizing the phase transition of liquid metals, the segregation of precursors in the bulk can be controlled, leading to self limited growth. By utilizing the fluidity of the liquid metals, 2D material crystals can achieve self assembly on their surface, including oriented stitching, ordered assembly, and heterostacking, which enables the creation of new multilevel or hybrid structures, leading to property and function extension and even the emergence of new physics. Finally, the unique liquid characteristic of liquid metals can also offer us new ideas about the transfer process. By utilizing the shear transformation of liquid metals, the direct sliding transfer of 2D materials onto arbitrary substrates can be realized. The research concerning the self limited growth, self assembly, and sliding transfer of 2D materials on liquid metals is just raising the curtain on the behavioral study of 2D materials on liquid metals. We believe these primary technology developments revealed by liquid metals will establish a solid foundation for both fundamental research and practical application of 2D materials.
author_names: Mengqi Zeng

Lei Fu
title: Controllable Fabrication of Graphene and Related Two Dimensional Materials on Liquid Metals via Chemical Vapor Deposition.
venue: Accounts of chemical research
year: 2018