Chemical Vapor Deposition Growth Research Articles

High yield and wide lateral size growth of α-Mo2C: exploring the boundaries of CVD growth of bare MXene analogues

Synthesis of Mo2C bare MXenes, without surface terminations groups, via chemical vapor deposition (CVD) on metal foils is scientifically a very intriguing crystal growth process, and there are still challenges and limited fundamental understanding to overcome to obtain high yield and wide crystal size lateral growth. Achieving large area coverage via direct growth is scientifically vital to utilize the full potential of their unique properties in different applications. In this study, we sought to expand the boundaries of the current CVD growth approach for Mo2C MXenes and gain insights into the possibilities and limitations of large area growth, with a particular focus on controlling Mo concentration. We report a facile modification of their typical CVD growth protocol and show its influence on the Mo2C synthesis, with growth times spanning up to 3 h. Specifically, prior to initiating the CVD growth process, we introduced a holding step in temperature at 1095 °C. This proved to be beneficial in increasing the Mo concentration on the liquid Cu growth surface. We achieved an average Mo2C crystals coverage of approximately 50% of the growth substrate area, increased tendency of coalescence and merging of individual flakes, and lateral flake sizes up to 170 μm wide. To gain deeper understanding into their CVD growth behavior, we conducted a systematic investigation of the effect of several factors, including (i) a holding step time on Mo diffusion rate through molten Cu, (ii) the Cu foil thickness over the Mo foil, and (iii) the CVD growth time. Phase, chemical and microstructural characterization by x-ray diffraction, x-ray photon spectroscopy, SEM and scanning/transmission electron microscopy revealed that the grown crystals are single phase α-Mo2C. Furthermore, insights gained from this study sheds light on crucial factors and inherent limitations that are essential to consider and may help guide future research progress in CVD growth of bare MXenes.

Reconfiguring nucleation for CVD growth of twisted bilayer MoS2 with a wide range of twist angles

Twisted bilayer (TB) transition metal dichalcogenides (TMDCs) beyond TB-graphene are considered an ideal platform for investigating condensed matter physics, due to the moiré superlattices-related peculiar band structures and distinct electronic properties. The growth of large-area and high-quality TB-TMDCs with wide twist angles would be significant for exploring twist angle-dependent physics and applications, but remains challenging to implement. Here, we propose a reconfiguring nucleation chemical vapor deposition (CVD) strategy for directly synthesizing TB-MoS2 with twist angles from 0° to 120°. The twist angles-dependent Moiré periodicity can be clearly observed, and the interlayer coupling shows a strong relationship to the twist angles. Moreover, the yield of TB-MoS2 in bilayer MoS2 and density of TB-MoS2 are significantly improved to 17.2% and 28.9 pieces/mm2 by tailoring gas flow rate and molar ratio of NaCl to MoO3. The proposed reconfiguring nucleation approach opens an avenue for the precise growth of TB-TMDCs for both fundamental research and practical applications.

Low-temperature synthesis of uniform monolayer molybdenum disulfide films

Monolayer molybdenum disulfide (MoS2) has garnered significant attention owing to its potential applications in electronics and optoelectronics. Nevertheless, existing methods for the chemical vapor deposition growth of MoS2 demand elevated synthesis temperatures and involve transfer procedures, thereby restricting its effectiveness in device manufacturing. In this study, we present the direct growth of 1-in. (∼25 mm) monolayer MoS2 films on SiO2 and other substrates under low-temperature conditions (360 °C). We employed a highly reactive substance, MoO2Cl2, as the molybdenum source for growth, which significantly reduces the growth temperature of MoS2. Simultaneously, a transitional temperature zone was implemented to further lower the growth temperature of MoS2. Experimental results from multiple tests on the produced MoS2 films indicated excellent uniformity and relatively large grain size (∼5 μm) at the low growth temperature, ensuring its promising applicability Furthermore, we fabricated field-effect transistors on the SiO2, achieving a mobility of 14.3 cm2 V−1 s−1 and an Ion/Ioff ratio exceeding 105. Our method offers a versatile approach for the low-temperature growth of MoS2, paving the way for future developments in silicon process-compatible applications.

Theoretical study on the nucleation control of WS<sub>2 </sub>on Au(111) surfaces

Two-dimensional tungsten disulfide (WS<sub>2</sub>), as a semiconductor material with unique layer-dependent electronic and optoelectronic characteristics, demonstrates a promising application prospect in the field of optoelectronic devices. The fabrication of wafer-scale monolayer WS<sub>2</sub> films is currently a critical challenge that propels their application in advanced transistors and integrated circuits. Chemical vapor deposition (CVD) is a feasible technique for fabricating large-area, high-quality monolayer WS<sub>2</sub> films, yet the complexity of its growth process results in low growth efficiency and inconsistent film quality of WS<sub>2</sub> .In order to guide experimental efforts to diminish grain boundaries in WS<sub>2</sub> ,thereby improving film quality to enhance electronic performance and mechanical stability, this study investigates the nucleation mechanisms of WS<sub>2</sub> during CVD growth through first-principles theoretical calculations. By considering chemical potential as a crucial variable, we analyze the growth energy curves of WS<sub>2</sub> under diverse experimental conditions. Our findings demonstrate that modulating the temperature or pressure of the tungsten and sulfur precursors can decisively influence the nucleation rate of WS<sub>2</sub>. Notably, the nucleation rate reaches a peak at a tungsten source temperature of 1250 K, while an increase in sulfur source temperature or a decrease in pressure can suppress the nucleation rate, thereby enhancing the crystallinity and uniformity of monolayer WS<sub>2</sub>. These insights not only furnish a robust theoretical foundation for experimentally fine-tuning the nucleation rate as needed but also provide strategic guidance for optimizing experimental parameters to refine the crystallinity and uniformity of monolayer WS<sub>2</sub> films. Such advancements are expected to accelerate the deployment of WS<sub>2</sub> materials in a range of high-performance electronic devices, marking a significant stride in the field of materials science and industrial applications.

Chemical vapor deposition growth of graphene and other nanomaterials with 3D architectures towards electrocatalysis and secondary battery-related applications.

Recently, two-dimensional (2D) layered materials, such as graphene and transition metal dichalcogenides (TMDCs), have garnered a lot of attention in energy storage/conversion-related fields due to their novel physical and chemical properties. Constructing flat graphene and TMDCs nanosheets into 3D architectures can significantly increase their exposed surface area and prevent the restacking of adjacent 2D layers, thus dramatically promoting their applications in various energy-related fields. Chemical Vapor Deposition (CVD) is a low-cost, facile, and scalable method, which has been widely employed to produce high-quality graphene and TMDCs nanosheets with 3D architectures. During the CVD process, the morphologies and properties of the 3D architectures of such 2D materials can be designed by selecting substrates with different compositions, stacking geometries, and micro-structures. In this review, we focus on the recent advances in the CVD synthesis of graphene, TMDCs, and their hybrids with 3D architectures on different 3D-structured substrates, as well as their applications in the electrocatalytic hydrogen evolution reaction (HER) and various secondary batteries. In addition, the challenges and future prospects for the CVD synthesis and energy-related applications of these unique layered materials will also be discussed.

Recent trends in the transfer of graphene films.

Recent years have witnessed advances in chemical vapor deposition growth of graphene films on metal foils with fine scalability and thickness controllability. However, challenges for obtaining wrinkle-free, defect-free and large-area uniformity remain to be tackled. In addition, the real commercial applications of graphene films still require industrially compatible transfer techniques with reliable performance of transferred graphene, excellent production capacity, and suitable cost. Transferred graphene films, particularly with a large area, still suffer from the presence of transfer-related cracks, wrinkles and contaminants, which would strongly deteriorate the quality and uniformity of transferred graphene films. Potential applications of graphene films include moisture barrier films, transparent conductive films, electromagnetic shielding films, and optical communications; such applications call different requirements for the performance of transferred graphene, which, in turn, determine the suitable transfer techniques. Besides the reliable transfer process, automatic machines should be well developed for the future batch transfer of graphene films, ensuring the repeatability and scalability. This mini-review provides a summary of recent advances in the transfer of graphene films and offers a perspective for future directions of transfer techniques that are compatible for industrial batch transfer.

Atomic insight into the effects of precursor clusters on monolayer WSe2.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have been attracting much attention due to their rich physical and chemical properties. At the end of the chemical vapor deposition growth of 2D TMDCs, the adsorption of excess precursor clusters onto the sample is unavoidable, which will have significant effects on the properties of TMDCs. This is a concern to the academic community. However, the structures of the supported precursor clusters and their effects on the properties of the prepared 2D TMDCs are still poorly understood. Herein, taking monolayer WSe2 as the prototype, we investigated the structure and electronic properties of SeN, WN (N = 1-8), and W8-NSeN (N = 1-7) clusters adsorbed on monolayer WSe2 to gain atomic insight into the precursor cluster adsorption. In contrast to W clusters that tightly bind to the WSe2 surface, Se clusters except for Se1 and Se2 are weakly adsorbed onto WSe2. The interaction between W8-NSeN (N = 1-7) clusters and the WSe2 monolayer decreases with the increase in the Se/W ratio and eventually becomes van der Waals interaction for W1Se7. According to the phase diagram, increasing the Se/W ratio by changing the experimental conditions will increase the ratio of SeN and W1Se7 clusters in the precursor, which can be removed by proper annealing after growth. W clusters induce lots of defect energy levels in the band gap region, while the adsorption of W1Se7 and SeN clusters (N = 3-6, 8) promotes the spatial separation of photo generated carriers at the interface, which is important for optoelectronic applications. Our results indicate that by controlling the Se/W ratio, the interaction between the precursor clusters and WSe2 as well as the electronic properties of the prepared WSe2 monolayer can be effectively tuned, which is significant for the high-quality growth and applications of WSe2.

Growth of Single-Walled Carbon Nanotubes from Solid Supported Heterogeneous Catalysts: Achievements and Challenges

Single-walled carbon nanotubes (SWNTs) have gained worldwide attention because of their exceptional electronic, optical, and mechanical properties, which are contingent on their structures denoted by chiral indices (n, m). To fully harness the extraordinary properties and advance SWNT-based technology, large scale synthesis of SWNTs with a narrow chirality distribution or even a specific (n, m) is highly demanded. Among various SWNT preparation techniques, chemical vapor deposition growth from solid supported heterogeneous catalysts has emerged as a promising approach in terms of large yield and (n, m) structure control. In this review, we provide an overview of the progress in developing heterogeneous catalysts for bulk synthesis of SWNTs. Firstly, the advantages and disadvantages of using solid supported catalysts for chemical vapor deposition growth of SWNTs are discussed. Secondly, the key components in supported catalysts, including the metallic component and the nature of support material, as well as their respective roles in affecting the catalyst performances and SWNT chirality distribution, are highlighted. Finally, the current challenges and future directions in the field of SWNT synthesis from solid supported catalysts are proposed.

Effect of substrate roughness on the nucleation and growth behaviour of microwave plasma enhanced CVD diamond films – a case study

The influence of substrate surface roughness on the nucleation and growth of diamond films by chemical vapour deposition (CVD) is investigated. Silicon substrates were grinded with six different grit sizes of abrasive papers with a rotating wheel. Si was also etched by Ar+ ions to produce average surface roughness Ra = 11.29 nm on the mirror polished side (Ra = 1.17 nm). A comparison of the results of the effect of substrate roughness, on the growth behaviour of nanocrystalline diamond (NCD) films, by using both the resonant cavity and the linear antenna CVD systems, are presented here. Scanning electron microscopy (SEM) images and Raman spectroscopy reveal that under both the linear antenna and the resonant cavity microwave plasma CVD conditions, grown films are NCD. The diamond nanocrystals sizes vary from 80 to 180 nm, grown by both the reactors after few hours of deposition, irrespective of the substrate roughness, whereas their quality (defined by the relative percentage ratios of the Raman sp3 peak intensity to the non-sp3 peak intensity) varies from 33% to 45%, depending on the substrate surface roughness. Such nanocrystals grew into plate-like flat 1–6 μm size diamond grains after prolonged hours (64–69 h) of CVD growth. It is found specifically that the roughness created by the argon plasma treatment of the silicon substrate surfaces effectively enhances the nucleation and growth behaviour of the diamond films.

Probing and controlling oxygen impurity diffusion in h-BN semi-bulk crystals

Combining its unique features of ultrawide bandgap (UWBG) and two-dimensional nature, h-BN has been explored for emerging applications such as deep ultraviolet optoelectronic devices and single photon emitters. One of the unusual applications of h-BN is for solid-state neutron detectors by utilizing the property of high thermal neutron capture cross section of B-10 as well as its UWBG properties. Although a record high detection efficiency of 59% has been attained by h-BN detectors, the understanding/minimization of defects and impurities is still needed to further advance the h-BN material and detector technologies. We report metal organic chemical vapor deposition growth and oxygen (O) impurity diffusion in thick h-BN. The diffusion coefficient (D) of O impurities has been measured via the evolution of an oxygen related emission with the etching depth, providing a value of D of ∼ 2 × 10−13 cm2/s at 1450 °C and supporting the interpretation that oxygen in h-BN is a substitutional donor. A multiple-buffer-layer approach was employed to mitigate to a certain degree the issue of oxygen diffusion from sapphire substrate during growth. It was demonstrated that the performance of h-BN neutron detectors fabricated from the wafer incorporating multiple buffer layers was significantly improved, as manifested by the enhanced thermal neutron detection efficiency. The advancement of the crystal growth technology of h-BN semi-bulk crystals creates applications in optoelectronic and power electronic devices utilizing the UWBG semiconductor properties of h-BN, while high efficiency h-BN neutron detectors have the potential to supplant the traditional He-3 gas detectors in various application areas by offering the obvious advantages of UWBG semiconductor technologies.

In Situ Growth of High-Quality Single-Crystal Twisted Bilayer Graphene on Liquid Copper.

Twisted bilayer graphene (TBG) generates significant attention in the fundamental research of 2D materials due to its distinct twist-angle-dependent properties. Exploring the efficient production of TBG with a wide range of twist angles stands as one of the major frontiers in moiré materials. Here, the local space-confined chemical vapor deposition growth technique for high-quality single-crystal TBG with twist angles ranging from 0° to 30° on liquid copper substrates is reported. The clean surface, pristine interface, high crystallinity, and thermal stability of TBG are verified by using comprehensive characterization techniques including optical microscopy, electron microscopy, and secondary-ion mass spectrometry. The proportion of TBG in bilayer graphene reaches as high as 89%. In addition, the stacking structure and growth mechanism of TBG are investigated, revealing that the second graphene layer develops beneath the first one. A series of comparative experiments illustrates that the liquid copper surface, with its excellent fluidity, promotes the growth of TBG. Electrical measurements show the twist-angle-dependent electronic properties of as-grown TBG, achieving a room-temperature carrier mobility of 26640 cm2 V-1 s-1 . This work provides an approach for the in situ preparation of 2D twisted materials and facilitates the application of TBG in the fields of electronics.

Growth of 2D Cr2 O3 -CrN Mosaic Heterostructures with Tunable Room-Temperature Ferromagnetism.

2D magnets have generated much attention due to their potential for spintronic devices. Heterostructures of 2D magnets are interesting platforms for exploring physical phenomena and applications. However, the controlled growth of 2D room-temperature ferromagnetic heterostructures is challenging. Here, one-pot chemical vapor deposition growth of stable 2D Cr2 O3 -CrN mosaic heterostructures (MHs) is reported with a controlled ratio of components that possess robust room-temperature ferromagnetism. The 2D MHs consist of Cr2 O3 flakes with embedded CrN subdomains and the CrN:Cr2 O3 ratio can be tuned from 0% to 100% during growth. By changing the CrN:Cr2 O3 ratio, the ferromagnetism of the MHs (e.g., saturation magnetization, coercive field), which originates from the interfacial coupling between Cr2 O3 and CrN, can be controlled. Importantly, the obtained Cr2 O3 -CrN MHs are stable in air at elevated temperatures and have robust ferromagnetism with Curie temperature >400K. This work presents a facile method for fabricating 2D MHs with tunable magnetism which will benefit high-temperature spintronics.

A systematic study on the efficacy of low-temperature GaN regrown on p-GaN to suppress Mg out-diffusion

Embedding p-type gallium nitride (p-GaN) in AlxGa1-xN-based thin films has garnered significant interest as a versatile structure for bandgap engineering such as tunnel/super-junctions or current blocking/guiding functions in electronic devices. However, Mg, a p-GaN dopant, has an undesirable diffusive capacity into the nearby thin films at a high growth temperature (>1,000°C), resulting in structural challenges in device design. This study systematically investigated the low-temperature GaN (LT-GaN) layer regrown on p-GaN that suppresses Mg diffusion according to metal–organic chemical vapor deposition growth conditions. Prototype Al0.3Ga0.7N (40 nm)/GaN (140 nm) high-electron-mobility transistors (HEMTs) were regrown with LT-GaN on p-GaN (300 nm), and a high two-dimensional electron gas (2DEG) density of 3.13E12 cm−2 was achieved by inserting a 100-nm-thick LT-GaN layer grown at 750°C; in contrast, only 1.76E10 cm−2 2DEG density was obtained from Al0.3Ga0.7N/GaN HEMTs regrown directly on p-GaN (Mg: 4.0E19 cm−3). The fabricated Al0.3Ga0.7N/GaN HEMTs with 100-nm-thick LT-GaN demonstrated a high drain current density of 84.5 mA/mm with a low on-state resistance of 31 Ω·mm. The AlxGa1-xN/LT-GaN/p-GaN platform demonstrated here paves the way for various III-nitride-based structures with embedded p-GaN.

Chemical vapor deposition growth of [formula omitted] on Si- and C- face off-axis 4H–SiC at high temperature

Realization of β‐Ga2O3 on a high-thermal-conductivity substrate is crucial to overcome the poor thermal conductivity of β‐Ga2O3 which is one of the major roadblocks against its era in power electronics. We investigated low-pressure chemical vapor deposition (LPCVD) growth on both Si and C- face (0001) 4H–SiC at a high growth temperature of 925 °C using Ga metal and O2 gas source. Growths on C-face 4H–SiC resulted polycrystalline β‐Ga2O3 for the entire O2-flow range, whereas under optimized O2-flow conditions, step flow growth of (−201) β‐Ga2O3 was achieved on Si-face 4H–SiC with 3.7 nm rms surface roughness and rocking curve FWHM of 0.54° at a growth rate reaching 2.48 μm/h 4° off-axis nature of the substrate promoted the growth of some of the in-plane rotational domains while suppressing others. Raman measurements further verified the pure β‐Ga2O3 nature of the grown films. Using a customized LPCVD with solid source Ga, a cost-effective, safe and industrially scalable method was shown to pave the way to enable β‐Ga2O3 heteroepitaxy on 4H–SiC for high-power electronics.

Toward an understanding of the mechanism of mixed-salt-mediated CVD growth of MoSe2

The use of liquid precursors in chemical vapor deposition (CVD) techniques is advantageous for growing large-area, uniform two-dimensional (2D) transition-metal dichalcogenides (TMDs) compared to conventional methods using solid precursors. While various liquid precursors have been explored, recent studies highlight the use of mixed-salt precursors for growing uniform and wafer-scale TMDs. In this study, we propose a growth mechanism and present our findings on the epitaxial growth of MoSe2 domains as a function of annealing/growth time and H2 flow rate using Na2MoO4 and Na2SeO3 mixed-salt precursors. We confirm that the increase in the annealing time enhances the distribution of spin-coated precursors, leading to a rise in flake number density. On the other hand, prolonged growth time results in better-aligned MoSe2 flakes along the c-sapphire substrate step-edges. A significant finding is the dynamic diffusion of dendritic structures within large domains over the growth period, owing to the constant dissolution and recrystallization in the presence of residual liquid alloys. An increase in the H2 flow during CVD growth yields small, triangular domains aligned with the step edges, a result of the efficient reduction of precursor alloys and subsequent selenization. Our results provide an insight on achieving uniform and aligned morphology in CVD growth of 2D TMDs using liquid-phase precursors, a crucial step toward large-area fabrication.

Discovery of Graphene Growth Alloy Catalysts Using High-Throughput Machine Learning.

Despite today's commercial-scale graphene production using chemical vapor deposition (CVD), the growth of high-quality single-layer graphene with controlled morphology and crystallinity remains challenging. Considerable effort is still spent on designing improved CVD catalysts for producing high-quality graphene. Conventionally, however, catalyst design has been pursued using empirical intuition or trial-and-error approaches. Here, we combine high-throughput density functional theory and machine learning to identify new prospective transition metal alloy catalysts that exhibit performance comparable to that of established graphene catalysts, such as Ni(111) and Cu(111). The alloys identified through this process generally consist of combinations of early- and late-transition metals, and a majority are alloys of Ni or Cu. Nevertheless, in many cases, these conventional catalyst metals are combined with unconventional partners, such as Zr, Hf, and Nb. The approach presented here therefore highlights an important new approach for identifying novel catalyst materials for the CVD growth of low-dimensional nanomaterials.

Advanced approach of bulk (111) 3C-SiC epitaxial growth

3C-SiC films grown on (111) Si substrates exhibit poor crystal quality and experience wafer cracks and bowing preventing access to bulk growth. This work reports innovative Chemical Vapor Deposition (CVD) growth methodology on 4 in. Si substrates which allowed the growth of 230 mm thick layer of (111) 3C-SiC through the melting of the Si substrate in the CVD chamber and the adoption of the resulting free standing 3C-SiC for the growth of bulk (111) 3C-SiC layer under high N fluxes. From the molten KOH etching and subsequent SEM investigation it has been ascertained that with a N2 flux of 1600 sccm there is a significant reduction in the concentration of stacking faults (SFs) from (7.16 ± 0.04) × 103 cm−1 to (0.4 ± 0.3) × 103 cm−1. This reduction is consistent with the cross section m-PL response displaying steep and uniform increase in the intensity of the band-edge signal a factor 10 higher on the surface with respect to the equal (100) 3C-SiC grown thickness. Furthermore, the emission attributed to point defects is considerably lower in (111) 3C-SiC. From Scanning Transmission Electron Microscopy (STEM) investigation it appears evident how the typical mechanism valid in (100) growths consisting in the mutual closure of SFs coming from opposing {111} planes that give rise to Lomer and l-shaped dislocations is replaced by a different panorama of evolution. Indeed, it is shown how the SFs shred but do not interrupt each other during growth. Furthermore, dropping in the number of atomic planes composing SFs layers appears to be a key phenomenon leading to both the shrinkage of the number of SF atomic layers as well as to the SF self-closure. High Angle Annular Dark Field-Scanning Transmission Electron Microscopy (HAADF-STEM) attested how the crystal tends to smooth out the lattice mismatch until the SF is suppressed. Because of the foregoing, the mechanisms of evolution of the defects in (111) 3C-SiC revealed in this study, demonstrates how the growth parameters must be matched with the kinetics of the defects in order to endorse (111) 3C-SiC adoption in high performing devices.

Low-Temperature Centimeter-Scale Growth of Layered 2D SnS for Piezoelectric Kirigami Devices.

Tin monosulfide (SnS) is a promising piezoelectric material with an intrinsically layered structure, making it attractive for self-powered wearable and stretchable devices. However, for practical application purposes, it is essential to improve the output and manufacturing compatibility of SnS-based piezoelectric devices by exploring their large-area synthesis principle. In this study, we report the chemical vapor deposition (CVD) growth of centimeter-scale two-dimensional (2D) SnS layers at temperatures as low as 200 °C, allowing compatibility with processing a range of polymeric substrates. The intrinsic piezoelectricity of 2D SnS layers directly grown on polyamides (PIs) was confirmed by piezoelectric force microscopy (PFM) phase maps and force-current corroborative measurements. Furthermore, the structural robustness of the centimeter-scale 2D SnS layers/PIs allowed for engraving complicated kirigami patterns on them. The kirigami-patterned 2D SnS layer devices exhibited intriguing strain-tolerant piezoelectricity, which was employed in detecting human body motions and generating photocurrents irrespective of strain rate variations. These results establish the great promise of 2D SnS layers for practically relevant large-scale device technologies with coupled electrical and mechanical properties.

Recent progress on chemical vapor deposition growth of 2D materials

Remarkable progress has been made to understand the chemical vapor deposition (CVD) of two-dimensional (2D) materials over the last two decades. The review summarized the state-of-the-art experimental synthesis and modelling and simulation on 2D materials CVD growth. Firstly, the family of 2D materials, and their CVD growth processes are introduced. Secondly, the experimental synthesis and modelling and simulation on graphene growth are discussed. In particular, the applications of reactive molecular dynamics methods, kinetic Monte Carlo and density-functional theory in 2D material growth are addressed. Then, the CVD growth of hexagonal boron nitride and transition metal dichalcogenides are further discussed, focusing on the effects of reaction conditions (growth temperature, pressure, vapour-phase composition, etc.) on the domain morphologies, edge structures and grain boundaries of 2D materials. Last, conclusions and outlooks are presented.

Supported catalysts derived from cobalt phyllosilicates for chemical vapor deposition growth of single-walled carbon nanotubes

Chemical vapor deposition (CVD) growth of single-walled carbon nanotubes (SWNTs) using supported catalyst is problematic due to possible metal coalescence during reaction. Thus, the development of supported catalyst that resists sintering is crucial for synthesizing SWNTs with a narrowly distributed chirality. Here, silica-supported phyllosilicate materials containing Co are prepared for catalytically growing carbon nanotubes. Owing to the incorporation of Co in the phyllosilicate, only part of Co2+ is reduced under CVD reaction environment, leading to the formation of immobilized metallic particles which subsequently catalyze the growth of SWNTs at 850 °C. With the addition of Pd promoter, the reducibility and carburization of the Co particles is enhanced, leading to the preferential synthesis of (6, 5) SWNTs at 600 °C. This work extends the application of phyllosilicates in catalytic synthesis of SWNTs, thus providing a new avenue for chirality-selective synthesis of SWNTs.