Twisted Multilayer MoS2 Growth on SrTiO3 for 2D materials

Monolayer two dimensional (2D) transition metal dichalcogenides (TMDs) are recent emerged one among all other optoelectronic material, because of its strong light−matter interactions for direct bandgap. However, these multilayer counter parts exhibited an indirect bandgap resulting to poor quantum yield of photon emission. Sinu Mathew and his collaborators have been reported on the strong direct bandgap-like photoluminescence (PL) at ∼1.9 eV, a multilayer MoS₂ grown on SrTiO₃ in ACS Nano on November 2020. They found that the intensity is significantly higher than the observed multilayer MoS₂/SiO₂. However, it affects the evolution of band structure in multilayer MoS₂ which causes the higher photo carrier recombination for the direct bandgap. To enable multilayer TMDs for robust optical device applications, these results will provide a suitable platform. In this research, they have demonstrated a strong direct bandgap-like PL emission via chemical vapor deposition (CVD) growth multilayer MoS₂ on SrTiO₃ (STO), with an archetypal perovskite transition metal oxide substrate [1].

2D transition materials are characterized of weak out-of-plane van der Waal (vdW) forces even without lattice or interlayer crystallographic orientation matching which can easily stack them to the formation of vertical heterostructures. It can be seen that the 2D materials families will have the monolayers of TMD semiconductors, which can exhibit several intriguing properties like strong direct bandgap photoluminescence (PL). MoS₂have been popular in the visible range with tightly bound excitons and trions [2].

In 2D materials, TMDs has attracted an significant interest on the evolution of interlayer coupling and its dramatic effects on band response in structural features. Meanwhile, the monolayers have direct bandgap, bilayer and multilayer TMDs are indirect bandgap, which results to a very weak PL emission. It can also be seen that the multilayers have exhibited indirect bandgap and low PL yield, the increase of optical density with the thickness is a challenging one and for the enhancement of this yield would be required modification in the band structure. However, there are some effort in this direction, that led to two major approaches [3]:

Intercalation of light atomic species in the van der Waals gap.
Fabrication of bilayer heterostructures with an interlayer twist.

As per supportive evidence, the MoS₂ domains are randomly oriented and their relative orientation layers would be different during the coalesce of continuous film formation. Hence, this results to an interlayer twist, which could cause the multilayer MoS₂ film deviation from conventional 2H configuration. Notably, to illustrate the strong luminescence from the twisted multilayer samples, an interlayer twist will influence PL intensity, and the changes observed are not adequate. For instance, the interlayer twist in bilayer MoS₂/SiO₂will not considerably enhance the PL emission intensity. Meanwhile for twisted bilayer MoS₂/STO, the change in PL intensity between a twisted bilayer and a monolayer sample would be negligible (almost 0.7% of the monolayer).

Figure 1. Schematic diagram, the crystal structure of a 2-H oriented bilayer MoS₂compared with the crystal structure of twisted MoS₂/STO [1].

An observation of strong direct bandgap-like PL from multilayer MoS₂ grown on STO at 1.9 eV is mainly due to the combined effect of interlayer twist and enhanced vdW gap. The possible reason for the enhanced vdW gap separation on the samples is mainly due to growth of multilayer MoS₂ exposure at elevated temperatures for a prolonged period of time. This will cause oxygen out diffusion from the STO lattice. As per the previous reports, similar oxygen out diffusion was observed in oxide thin film heterostructures. Therefore, in their results they predict that the oxygen in their case might be intercalated between the MoS₂ which lead to further expansion of the vdW gap resulting to an enhanced interlayer decoupling [4,5].

One of the main key differences in the growth of multilayer MoS₂ on STO is to compared their growth on SiO₂which induced interlayer twist and mild self-intercalation of oxygen, the oxygen in STO is highly mobile at a growth temperature of ∼700 °C. Hence, this weakens the interlayer coupling, which leads to a strong light emission. It can also be an interesting fact that the exploration the multilayer growth TMDs on complex oxide perovskites similar to that of SrTiO₃ such as BaTiO₃ and EuTiO₃, which exhibit structural phase transitions, spontaneous charge ordering.

Our SNB team have emphasize this research article to enrich our viewer’s knowledge about the twisted multilayer MoS₂ growth on SrTiO₃ for a strong photoluminescence. Observation of strong PL emission from multilayer MoS₂ samples can enable its use for the applications. This require a strong PL emission and absorption such as nanoscale detectors and light emitters where they used only the monolayers. Being a single layer of atoms, monolayer MoS₂and other related TMDs are sensitive to ambient, that degrades its performance in over time. Thus, the observation of strong PL emission from multilayered MoS₂ could offer a better solution which would be more stable in the performance. Therefore, a fundamental perspective, like mixed dimensional heterostructures can provide additional pathways to achieve optoelectronic tunability in 2D semiconductors.

References

S. Sarkar et al., ACS Nano (2020),https://dx.doi.org/10.1021/acsnano.0c04801.
G. Wang, et al., Rev. Mod. Phys. 90, 021001 (2018).
R.Dhall,et al.,Adv. Mater., 27, 1573 (2015).
De Souza, Adv. Funct. Mater., 25, 6326 (2015).
L.Hu, et al.,Appl. Phys. Lett. 105, 111607 (2014).

--- Dr. Y. Sasikumar

Author Profile

Comments

PROSPECTS ON PHOTOBIOREFINERY

Very recently, Prof. Dr. K. Faungnawakij and his research group have summarized a mini review report on an emerging renewable technique of Photobiorefinery . This is one of the beyond technique of Artificial Photosynthesis (AP) [1] . Despite great promises, AP technologies for solar H2 production and CO2 reduction are far uncompetitive to other promising technologies at the current stage . However, despite an enormous effort, time, and budget paid on AP-related researches throughout several decades, AP technologies have struggled to strive beyond laboratory demonstration except a very few exceptions [2] . This bitter reality makes the translation of this excellent science to practical application questionable [3] . Technoeconomic analysis shows that without achieving the aggressive technology targets, this technology will not be commercially viable. This has directed the research community towards the development of highly efficient yet expensive devices. While tremendous p...

Impact on Climate and Land Use Changes Around Ganga River

In India, Ganga is the largest river and also famous spiritual river, in meantime pollution issue in Ganga river is considered to be one of the most discussed topics on river water quality in the past decades . The river gets s everely polluted with untreated industrial and human wastes, and the river crossed around 11 states in India and provides water for about 40% of India's population, approximately 500 million people, we couldn’t find more than any other river in the world [ 1, 2 ]. Central Pollution Control Board (CPCB) has mentioned that 764 grossly polluting industries were discharging into the Ganga river, 487 industries are from the Kanpur region. Therefore, the Kanpur region was treated as the main polluted spot and immediate action should be taken for further recovery of water quality. The Kanpur region is one of the most important industrialized place in India. It is the most polluted stretch of the Ganga River, because of its excessive pollutant discharge from the i...

Electric Vehicle: Public Health and Climate Benefits

A research team led by Daniel Peters at Northwestern University has investigated that if we introducing electrifying vehicles in the streets of the United States could annually prevent hundreds-to-thousands of premature accidental deaths.This work highlights the potential of a synergistic solution to reduce CO 2 emissions by hundreds to millions of tons annually. The estimate of economic damages induced by introducing electrifying vehicles (EV) adoption is substantial. With current infrastructure, about 25% of electrifying vehicles adoption in the US can save approximately $16.8 billion annually, has been told in the study entitled"Public Health and Climate Benefits and Trade offs of U.S. Vehicle Electrification," in GeoHealth on 13 th August 2020 [1] . Vehicle electrification in the United States could prevent hundreds to thousands of premature deaths annually while reducing carbon emissions by hundreds of millions of tons. This highlights the potential of co-beneficial...

Plasmonic Gold Nanoparticles as Designing Caps

Plasmonic nanomaterials have attracted significant interest because of its wide variety of applications such as sensing, energy conversion, photothermal therapy etc. Among the various plasmonic inorganic metals (Ag, Cu, Al, and Au) Au shows the excellent biocompatibility, chemical stability, and rich surface functionality. It can be seen that some new approaches have include the construction of metal shells on dielectric nanoparticles, and the control of island growth on nanoparticles and nanorods over the design of narrow gaps via nanoplates or nanoshells. Also, the conventional modulation of plasmonics via the control of shape, size and the aspect ratio of nanomaterials. The structural control have also arises from the active surface growth. As a result, the dynamic competition between ligand absorption and metal deposition occurs [ 1 ]. The properties of plasmonic nanostructures are highly dependent on its surface morphology, however, there are a very few methods for a...

Efficient Bio-Diesel Synthesis: Reusable Magnetic Catalysis

Prof. Anping Wang et al., with his research collaborative team from china ( 1. Guizhou University, China; and 2. Guizhou Normal University, China) and India (National Chemical Laboratory, India) have reviewed the research over views on the preparation methods, physicochemical properties, stabilization/functionalization, and the catalytic applications of magnetic materials, including magnetic acids, bases, enzymes, and acid-base bifunctional materials for the synthesis of bio-diesel. Here, we discuss only the preparation of efficient bio-diesel with merits and applications of magnetic nanocatalyst for the bio-diesel preparation . Bio-diesel products are mainly attain from bio mass feed stocks, which gives more attention in the biorefinery research affairs [1]. A green way of renewable liquid biofuels are emergency required one in present atmosphere. Among the various classes, best one is renewable diesel fuel, the chemical content of long-chain fatty acid methyl ester (FAME) or ethy...

Scientific Research Focus on “To End Hunger”

According to the Food and Agriculture Organization of the United Nations (FAO UN), Hunger Report, Ending hunger is a major objective of the United Nations’ (UN) Sustainable Development Goals (SDG), hunger is the term used to define periods when populations are experiencing severe food insecurity - means that they go for entire days without eating due to lack of money, lack of access to food, or other resources [ 1 ]. Hunger is strongly interconnected with poverty, and it involves interactions among an array of social, political, demographic, and societal factors. An attention is must in the following topics to put an end card for poor hunger: Global Hunger Index (GHI). World Food Program’s 2020. Global Report on Food Crises. Smallholder-farming. Ceres2030. The two main international institutions are the International Institute for Sustainable Development (IISD) and the International Food Policy Research Institute (IFPRI) , joined forces to estimate what it would cost to ...

Detection of Cancer via New Nano-Based Imaging Agents

New imaging agents were developed by physicians to detect cancer with better specificity and sensitivity. Further, they have the potential to significantly improve patient outcomes. It could offer enhanced premature cancer cells detection during routine screening and help the surgeons to identify tumor margins for surgical resection. Figure 1. In vivo visualization of 200 nm G8-liposomes imaged following intravenous injection [ 1 ]. Notice the bright accumulation and homogenous appearance of liposomes encapsulated with G8 dye (green). The vasculature region depicted here is of the mouse ear where real time flow video was taken at 30 fps. Scale bar represents 50 μm. Recently, Helen R. Salinas et al ., has evaluated the optical properties from a colorful class of pigments and dyes that humans routinely encounter [ 1 ]. These selective dyes and pigments are approved by Food and Drug Administration (FDA) which have utilized for the coloring of foods, drugs, and cosmetics. The authors...

A Biomimetic Eye with Perovskite Nanowire

The term “Biomimetics” derived from Ancient Greek, refers to life imitation. It is an interdisciplinary field in which comes from biology, engineering, and chemistry concepts. Biomimetics is applied to the synthesis of machines, or devices, which have functions that mimic real-life biological processes. Prof. Fan Zhiyoung , Department of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong SAR, China, and his team (from the University of California and Lawrence Berkeley National Laboratory, USA) has reported on the effective biological eye results with a new development “Biomimetic Eye” with supportive components such as hemispherical shape retina and perovskite nanowires [1] . Our eyes possess exceptional image and sensing nature, which selectively express the wide field of view, resolution, and sensitivity [2] . A specialty of biomimetic eye parts with such highlighted characteristics is a desirable one, speci...

RENEWABLE ENERGY'S ROLE IN ENVIRONMENTAL CLEEN-UP PROCESS

Human activity is overloading our atmosphere with carbon dioxide and other global warming emissions. These gases act like a blanket, trapping heat. The result is a web of significant and harmful impacts, from stronger, more frequent storms, to drought, sea level rise, and extinction. Most of global warming emissions come from our electricity sector. Most of those emissions come from fossil fuels like coal and natural gas . Sulfur dioxide (SO2) , which cause acid rain, comes from electricity generation. Nitrogen oxides (NOx) , which react with sunlight to create ground level ozone and smog, come from electricity generation. Ozone (O3) occurs naturally in the upper atmosphere where it is beneficial. Particulate matter is a type of air pollution more commonly referred to as soot. Carbon dioxide (CO 2 ) is a greenhouse gas that contributes to global climate change. Mercury is a highly toxic metal that is released from coal-fired power plants. In contra...

Detection and Diagnosis: Heavy Toxic Metals

Prof. Youzhi Li, from Hunan Agricultural University, Changsha, China and his research team have recently published, “Total concentrations and sources of heavy metal pollution in global river and lake water bodies from 1972 to 2017”. They discussed on heavy metals like lead (Pb) cause a severe threat to living beings because of its toxicity and bioaccumulation. Heavy metals like lead (Pb) cause a severe threat to living beings because of its toxicity and bioaccumulation. Amongst the heavy metals, lead (Pb) is the well-known one for its historical use in paints, petrol, and fuse joints in water pipes. Though the tradition of using Pb has been considerably decreased in recent years, Pb in drinking water still remains to be a problem for many societies around the world [ 1 ]. Hence, it is one of the supreme importance to monitor the levels of Pb in drinking water, so that contamination can be promptly identified and moderated. The World Health Organization (WHO) mentions a guideline l...

Search This Blog