Promoter-free synthesis of monolayer MoS2 by chemical vapour deposition (original) (raw)
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Advances in Condensed Matter Physics, 2022
Molybdenum disulfide (MoS2) is an actively pursuing material of the 2D family due to its semiconducting characteristics, making it a potential candidate for nano and optoelectronics application. MoS2 growth from molybdenum and sulphur precursors by chemical vapor depositions (CVD) is used widely, but molybdates’ conversion into MoS2 via CVD is overlooked previously. Direct growth of MoS2 on the desired pattern not only reduces the interfacial defects but also reduces the complexities in device fabrication. In this work, we combine the wet synthesis and chemical vapor deposition method where sodium molybdate and L-cysteine are used to make a solution. With the dip coating, the mixture is coated on the substrates, and then, chemical vapor deposition is used to convert the chemicals into MoS2. Raman spectroscopy revealed the presence of oxysulphides (peaks number value) other than A 1 g and E 2 g 1 , where heat treatment was performed in the presence of Ar gas flow only. On the other h...
Growth of MoS2 films: High-quality monolayered and multilayered material
AIP Advances
Transition-metal-dichalcogenide materials (TMDs) are proceeding toward future nanoelectronic devices as comprehensive research in this domain proves their extraordinary properties and potential for application in diverse fields. There are associated challenges related to the quality of grown material, grain size, and adaptiveness to a selected substrate, and chemical vapor deposition is considered the ideal technique in these regards. Salt-assisted growth of two-dimensional TMDs has recently solved some growth issues associated with the high melting points of some oxides and the low vapor pressure, which leads to limitations in the growth area. In the current study, NaCl-assisted growth is used to produce high-quality monolayered films on Si/SiO2 and multilayered films of MoS2 on fluorine-doped tin oxide. An empirical methodology was used to determine optimal conditions for sample growth. Factors such as precursor weights and ratios, temperature, and sulfurization were investigated ...
Materials
In the 2D material framework, molybdenum disulfide (MoS2) was originally studied as an archetypical transition metal dichalcogenide (TMD) material. The controlled synthesis of large-area and high-crystalline MoS2 remains a challenge for distinct practical applications from electronics to electrocatalysis. Among the proposed methods, chemical vapor deposition (CVD) is a promising way for synthesizing high-quality MoS2 from isolated domains to a continuous film because of its high flexibility. Herein, we report on a systematic study of the effects of growth pressure, temperature, time, and vertical height between the molybdenum trioxide (MoO3) source and the substrate during the CVD process that influence the morphology, domain size, and uniformity of thickness with controlled parameters over a large scale. The substrate was pretreated with perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) seed molecule that promoted the layer growth of MoS2. Further, we characterized ...
Chemistry of Materials, 2017
High-volume manufacturing of devices based on transition metal dichalcogenide (TMD) ultrathin films will require deposition techniques that are capable of reproducible wafer-scale growth with monolayer control. To date, TMD growth efforts have largely relied upon sublimation and transport of solid precursors with minimal control over vapor-phase flux and gas-phase chemistry, which are critical for scaling up laboratory processes to manufacturing settings. To address these issues, we report a new pulsed metal−organic chemical vapor deposition (MOCVD) route for MoS 2 film growth in a research-grade single-wafer reactor. Using bis(tert-butylimido)bis(dimethylamido)molybdenum and diethyl disulfide, we deposit MoS 2 films from ∼1 nm to ∼25 nm in thickness on SiO 2 /Si substrates. We show that layered 2H-MoS 2 can be produced at comparatively low reaction temperatures of 591°C at short deposition times, approximately 90 s for few-layer films. In addition to the growth studies performed on SiO 2 /Si, films with wafer-level uniformity are demonstrated on 50 mm quartz wafers. Process chemistry and impurity incorporation from precursors are also discussed. This low-temperature and fast process highlights the opportunities presented by metal−organic reagents in the controlled synthesis of TMDs.
ACS Omega, 2021
While the chemical vapor deposition technique can be used to fabricate 2D materials in a larger area, materials like MoS 2 have limited controllability due to their lack of selfcontrolling nature. This article presents a new technique for synthesizing a void-free millimeter-scale continuous monolayer MoS 2 film through the diffusion of a well-controlled Mo, Na, and seeding promoter-based coating under a low-pressure N 2 atmosphere. Compared to the conventional method, this technique provides precise control of solid precursors, where MoS 2 grows next to the coating. At 800°C, the synthesized MoS 2 showed a uniform single-layer MoS 2 film; however, a Na-free coating showed nanoscale voids and poor crystal quality, which are attributed to a higher edge-attachment barrier that slows down the MoS 2 lateral growth. The synthesized MoS 2 with Na-containing solution showed an intense PL peak with a 1.86 eV band gap. Even at the relatively low temperature of 700°C, compared to the Na-excluded condition, MoS 2 showed almost two times higher area coverage with a comparatively larger crystal size. This finding may assist in the future development of MoS 2-based electronic and optoelectronic devices such as transistors and photodetectors.
NaCl-assisted substrate dependent 2D planar nucleated growth of MoS2
Applied Surface Science, 2021
Synthesis of large-scale, uniform, easily transferable, and highly crystalline monolayer (1L) molybdenum disulfide (MoS2) on different substrates is a challenge and could decide its suitability for opto-electronic device applications. Herein, we report a facile NaCl-assisted Chemical Vapor Deposition (CVD) synthesis of high-quality MoS2 on amorphous, crystalline and layered substrates. Optical microscopy and Raman spectroscopy show that sapphire and SiO2/Si are suitable substrates for large 1L-MoS2 flakes growth, while mica is excellent for large-area continuous films. Comparatively lesser full-width-at-half-maximum (FWHM) of predominant A exciton peak (which is associated with direct band gap at K point) in photoluminescence spectra of 1L-MoS2 on sapphire suggests its high crystalline quality. However, 1L-MoS2 on other substrates, especially on quartz and bare Si show poor crystalline quality. The study depicts that the NaCl assists in the formation of seeding promoter such as water-soluble layer of Na2S and/or Na2SO4 on the substrate that helps in 2D planar nucleation of MoS2. The formation of such intermediate seeding layers also helps in layer transfer owing to its easy water solubility. The study could be utilized for large-scale synthesis of 1L-MoS2 on different substrates for high-performance optoelectronic devices.
Formation of nanosized monolayer MoS2 by oxygen-assisted thinning of multilayer MoS2
Journal of Applied Physics, 2016
We report the controllable nanosized local thinning of multi-layer (2 L and 3 L)-thickness MoS2 films down to the monolayer (1 L) thickness using the simple method of annealing in a dry oxygen atmosphere. The annealing temperature was optimized in the range of 240 °C to 270 °C for 1.5 h, and 1 L thick nanosized pits were developed on the uniform film of the 2 L and 3 L MoS2 grown using the chemical vapor deposition method. We characterized the formation of the 1 L nanosized pits using nanoscale confocal photoluminescence (PL) and Raman spectroscopy. We observed that the PL intensity increased and the Raman frequency shifted, representative of the characteristics of 1 L MoS2 films. A subsequent hydrogen treatment process was useful for removing the oxygen-induced doping effect resulting from the annealing.
Crystal Growth & Design, 2021
Direct growth of wafer scale high quality 2D layered materials (2DLMs) on SiO2/Si substrate is still a challenge. The chemical vapor deposition (CVD) technique has played a significant role in achieving a large area continuous film of 2DLMs. CVD growth requires the optimization of many growth parameters such as temperature, amount of precursors, pressure, carrier gas flow and distance between the reactants. However, the role of boundary layer of reactants concentration has not been explored yet. The amount of precursors which leads to the formation of reactants concentration boundary layer has a significant role in controlling the thickness of growing material. Here, we report the role of concentration boundary layer to achieve wafer-scale MoS2 in NaCl-assisted CVD growth at low temperature. Control of boundary layer thickness has led to the synthesis monolayer, bilayer, trilayer, and bulk MoS2 film and flakes in our single-zone CVD at atmospheric pressure. Most importantly, we have synthesized 7 × 2.5 cm 2 area continuous, high quality trilayer MoS2 film with good repeatability. We believe that our approach may lead to synthesize other wafer-scale 2DLMs that will pave the way for nano-and optoelectronics.