A novel crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit has been synthesized and carefully characterized in this work. By controlled sulfurization of monolayer MoSe2 the top layer of selenium atoms are substituted by sulfur atoms while the bottom selenium layer remains intact. The peculiar structure of this new material is systematically investigated by Raman, photoluminescence and X-ray photoelectron spectroscopy and confirmed by transmission-electron microscopy and time-of-flight secondary ion mass spectrometry. Density-functional theory calculations are performed to better understand the Raman vibration modes and electronic structures of the Janus SMoSe monolayer, which are found to correlate well with corresponding experimental results. Finally, high basal plane hydrogen evolution reaction (HER) activity is discovered for the Janus monolayer and DFT calculation implies that the activity originates from the synergistic effect of the intrinsic defects and structural strain inherent in the Janus structure.

Janus Monolayer Transition Metal Dichalcogenides

Two-dimensional crystals have emerged as a class of materials that may impact future electronic technologies. Experimentally identifying and characterizing new functional two-dimensional materials is challenging, but also potentially rewarding. Here, we fabricate field-effect transistors based on few-layer black phosphorus crystals with thickness down to a few nanometres. Reliable transistor performance is achieved at room temperature in samples thinner than 7.5 nm, with drain current modulation on the order of 10(5) and well-developed current saturation in the I-V characteristics. The charge-carrier mobility is found to be thickness-dependent, with the highest values up to ∼ 1,000 cm(2) V(-1) s(-1) obtained for a thickness of ∼ 10 nm. Our results demonstrate the potential of black phosphorus thin crystals as a new two-dimensional material for applications in nanoelectronic devices.

http://absimage.aps.org/image/MAR14/MWS_MAR14-2013-005031.pdf

Black Phosphorus Field-effect Transistors

In recent years, heterojunction materials bonded by interlayer van der Waals force have grown into a very large family. These van der Waals heterostructures have promising applications in photocatalysis due...

Recent progress of Van der Waals heterojunction applied in photocatalysis

We investigate the energetic stability and the structural and electronic properties of semiconductor/semiconductor and semiconductor/metal 2D van der Waals heterostructures composed by combinations of single layer InSe, bilayer phosphorene (BP), and graphene. For the semiconductor/semiconductor BP/InSe heterostructure, we found that the lowest (highest) unoccupied (occupied) states lie on the InSe (BP) layers, giving rise to a type-II band alignment, with electrons (holes) localized in the InSe (BP) layers. The semiconductor/metal interface composed by a single layer of InSe stacked on graphene (InSe/G) presents a $n$-type Schottky barrier, which can be tuned by applying an external electric field perpendicular to the InSe/G interface (${E}_{\ensuremath{\perp}}^{\mathrm{ext}}$). Upon further increase of ${E}_{\ensuremath{\perp}}^{\mathrm{ext}}$, the InSe/G contact becomes Ohmic, promoting a net charge transfer from the graphene sheet to the InSe layer, $n$-type doping. This is in contrast with the other semiconductor/metal van der Waals heterojunction, BP/G, where the BP sheet becomes $p$-type doped as a function of ${E}_{\ensuremath{\perp}}^{\mathrm{ext}}$. Exploiting the electron-hole separation in BP/InSe, and the formation of Ohmic contacts at the InSe/G and BP/G interfaces, we propose a $p\ensuremath{-}n$ junction composed by $p$-type BP and $n$-type InSe, with the graphene acting as electrodes and also as a source of electrons/holes in InSe/BP.

/pdf/two-dimensional-van-der-waals-p-n-junction-of-inse-1n798wh79l.pdf

Two-dimensional van der Waals p-n junction of InSe/Phosphorene

Inspired by natural photosynthesis, direct Z-scheme heterostructures are considered as promising photocatalysts for solar-driven water splitting and attract ever-growing interest. To date, it is still a challenge to achieve a high efficiency based on direct Z-scheme photocatalysts for overall water splitting, because suitable band gaps and overpotentials for both half-reactions and spatially separated catalytic sites should be fulfilled simultaneously in a photocatalytic system. These challenges can be solved by taking advantage of the intrinsic dipole effect for polarized materials. Here, we propose a new strategy to achieve this goal by constructing van der Waals (vdW) heterostructures based on two-dimensional (2D) polarized materials. Using density functional theory calculations, we predict a promising photocatalyst In2Se3/SnP3 heterostructure, with the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) taking place separately on the SnP3 and In2Se3 layers. It is found that the intrinsic dipole of the In2Se3 monolayer effectively enhances the redox abilities for both the HER and OER. Moreover, the intrinsic dipole can promote the spatial separation of photogenerated carriers, and also contributes to a high solar-to-hydrogen (STH) efficiency of 19.26%, which is quite promising for commercial applications. This work opens up an avenue for the design of highly efficient Z-scheme photocatalysts for overall water splitting.

Enhanced solar-to-hydrogen efficiency for photocatalytic water splitting based on a polarized heterostructure: the role of intrinsic dipoles in heterostructures

Constructing van der Waals (vdW) heterojunctions via stacking different two-dimensional materials is an effective approach to obtain desirable properties. By using the first-principles calculation, we explore the vdW heterojunction based on the Janus structure of the 1T-PtTe2 for the potential application in the excitonic solar cell. The SePtTe/InS vdW heterojunction is found to be an appropriate material with direct bandgap, high carrier mobility, high optical absorption, and staggered type-II band alignment. The donor bandgap is 1.08 eV in the Heyd–Scuseria–Ernzerhof (HSE) level. The optoelectronic properties are effectively modulated by both external electric field and vertical strain because inducing the redistribution of charge density in the interlayer. Within the HSE hybrid density functional, the donor bandgap can be tunable up to 1.38 eV. The high power conversion efficiency is tunable to 24.91%, while the flux of absorbed photons keeps beyond 4.41 mA/cm2. Our results indicate the potential application of the SePtTe/InS heterojunction in solar cell utilization.

Optoelectronic properties of type-II SePtTe/InS van der Waals heterojunction

Effect of non-isothermal retrogression and re-ageing on through-thickness homogeneity of microstructure and properties of Al-8Zn-2Mg-2Cu alloy thick plate

Constructing van der Waals (vdW) heterojunctions is an effective strategy for band engineering of two dimensional (2D) materials. The XM2X'/MX (M = Al, Ga, In; X = S, Se, Te) heterostructures are investigated by first-principles calculation. Five XM2X'/MX are found to be direct-band-gap type-II band structures with moderate band gap from 1.08 to 1.73 eV in HSE method, high optical absorption coefficient (~105cm-1) and broad absorption spectrum, which facilitates effective utilization of the solar visible light and separation of photo-generated electron-hole pairs. Intriguingly, the band gap and band offsets are tunable to achieve high power conversion efficiency by external electric field and vertical strain. These results indicate potential applications of the XM2X'/MX in solar energy conversion.

Excellent properties of type-II van der Waals Janus-XM2X’/MX heterojunctions toward solar cell utilization

Hybrid organic-inorganic perovskites is a class of materials with diverse chemically tunable properties and outstanding potential for multifunctionality. We use first-principles simulations to predict room temperature ferroelectricity in a representative of the formate family, [NH_{2}NH_{3}][Co(HCOO)_{3}]. The ferroelectricity arises as a "by-product" of structural transition driven by the stabilization of the hydrogen bond. As a consequence the coupling with the electric field is relatively weak giving origin to large intrinsic coercive fields and making material immune to the depolarizing fields known for its detrimental role in nanoscale ferroelectrics. Insensitivity to the electric field and the intrinsic dynamics of the order-disorder transition in such material leads to the supercoercivity defined as significant increase in the coercive field with frequency. Room temperature polarization measurements provide further support for the predictions.

/pdf/unusual-properties-of-hydrogen-bonded-ferroelectrics-the-1ugudgg4.pdf

Unusual Properties of Hydrogen-Bonded Ferroelectrics: The Case of Cobalt Formate.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Jialuo Ren

Author Tools

Chat about Author

Papers

Optoelectronic properties of type-II SePtTe/InS van der Waals heterojunction

Effect of non-isothermal retrogression and re-ageing on through-thickness homogeneity of microstructure and properties of Al-8Zn-2Mg-2Cu alloy thick plate

Excellent properties of type-II van der Waals Janus-XM2X’/MX heterojunctions toward solar cell utilization

Unusual Properties of Hydrogen-Bonded Ferroelectrics: The Case of Cobalt Formate.