Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Excitonic Dark States Shed Light on TMDC Atomic Layers: Berkeley Lab Discovery Holds Promise for Nanoelectronic and Photonic Applications

Berkeley Lab researchers have found evidence for excitonic dark states in monolayers of tungsten disulfide that could explain the unusual optoelectronic properties of single atomic layers of transition metal dichalcogenide (TMDC) materials.
Berkeley Lab researchers have found evidence for excitonic dark states in monolayers of tungsten disulfide that could explain the unusual optoelectronic properties of single atomic layers of transition metal dichalcogenide (TMDC) materials.

Abstract:
A team of Berkeley Lab researchers believes it has uncovered the secret behind the unusual optoelectronic properties of single atomic layers of transition metal dichalcogenide (TMDC) materials, the two-dimensional semiconductors that hold great promise for nanoelectronic and photonic applications.

Excitonic Dark States Shed Light on TMDC Atomic Layers: Berkeley Lab Discovery Holds Promise for Nanoelectronic and Photonic Applications

Berkeley, CA | Posted on September 11th, 2014

Using two-photon excitation spectroscopy, the researchers probed monolayers of tungsten disulfide, one of the most promising of 2D materials, and found evidence for the existence of excitonic dark states - energy states in which single photons can be neither absorbed nor emitted. These excitons were predicted from ab initio calculations by members of the research team to have an unusual energy sequence, plus excitonic binding energy and bandgaps that are far larger than was previously suspected for 2D TMDC materials.

"Discovery of very large excitonic binding energy and bandgaps and its nonhygrogenic nature in 2D semiconductor materials is important not only for understanding the unprecedented light-matter interaction arising from strong many-body effect, but also for electronic and optoelectronic applications, such as ultra-compact LEDs, sensors and transistors," says Xiang Zhang, director of Berkeley Lab's Materials Sciences Division and the leader of this study. "Such a large binding energy - 0.7eV - could also potentially make room-temperature excitons stable for future quantum computing efforts."

Zhang holds the Ernest S. Kuh Endowed Chair Professor at the University of California (UC) Berkeley, directs the National Science Foundation's Nano-scale Science and Engineering Center, and is a member of the Kavli Energy NanoSciences Institute at Berkeley. He and Berkeley Lab theoretical physicist Steven Louie, also with the Materials Sciences Division and UC Berkeley, are the corresponding authors of a paper in Nature that describes this research. The paper is titled "Probing excitonic dark states in single-layer tungsten disulphide." Co-authors are Ziliang Ye, Ting Cao, Kevin O'Brien, Hanyu Zhu, Xiaobo Yin, and Yuan Wang.

Excitons are bound pairs of excited electrons and holes that may cause significant deviations between photon absorption or emission energies and the electronic bandgaps that enable semiconductors to function in devices. 2D TMDC materials have generated quite a buzz in the electronics industry because they offer superior energy efficiency and carry much higher current densities than silicon. Furthermore, unlike graphene, the other highly touted 2D semiconductor, TMDCs have finite bandgaps. This makes them more device-ready than graphene, which has no natural bandgaps. However, questions marks hovering over the bandgap size and excitonic effect in 2D TMDCs have hampered their development.

"By experimentally revealing 2D excitonic dark states in a TMDC monolayer, we have demonstrated intense many-electron effects in this class of 2D semiconductors," says Ziliang Ye, a member of Zhang's research group and one of two lead authors of the Naturepaper. "Our discovery provides a basis for exploiting the unusual interactions between light and matter that result from strong excitonic effects, and should also enable better designs of heterostructures that involve TMDC monolayers."

In addition to LEDs and photodetectors, the discovery of strongly bound excitonic dark states could also hold important implications for "valleytronics," a highly promising potential new route to novel electronics and ultrafast data-processing.

"In valleytronics, information is encoded in a wave quantum number that describes which valley of the energy-momentum landscape a carrier belongs to as it moves through a crystal lattice," says Louie. "Our work provides new understanding and information on the photo-excited states, and on the resulting carriers where the valley information is encoded."

Says Ting Cao, a member of Louie's research group and the other lead author of the Nature paper, "2D TMDCs should be also well-suited for the next generation of flexible devices and wearable electronics."

This work was supported by the DOE Office of Science with computer time provided by the DOE National Energy Research Scientific Computing Center.

####

For more information, please click here

Contacts:
Lynn Yarris

510-486-5375

Copyright © DOE/Lawrence Berkeley National Laboratory

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

For more about the research of Xiang Zhang go here:

For more about the research of Steven Louie go here:

Download article:

Related News Press

News and information

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Two-dimensional bimetallic selenium-containing metal-organic frameworks and their calcinated derivatives as electrocatalysts for overall water splitting March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Physics

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Scientists use heat to create transformations between skyrmions and antiskyrmions January 12th, 2024

Focused ion beam technology: A single tool for a wide range of applications January 12th, 2024

Flexible Electronics

Electrons screen against conductivity-killer in organic semiconductors: The discovery is the first step towards creating effective organic semiconductors, which use significantly less water and energy, and produce far less waste than their inorganic counterparts February 16th, 2024

Laboratories

A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Govt.-Legislation/Regulation/Funding/Policy

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

Chip Technology

New chip opens door to AI computing at light speed February 16th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

Electrons screen against conductivity-killer in organic semiconductors: The discovery is the first step towards creating effective organic semiconductors, which use significantly less water and energy, and produce far less waste than their inorganic counterparts February 16th, 2024

NRL discovers two-dimensional waveguides February 16th, 2024

Quantum Computing

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

Physicists ‘entangle’ individual molecules for the first time, hastening possibilities for quantum information processing: In work that could lead to more robust quantum computing, Princeton researchers have succeeded in forcing molecules into quantum entanglement December 8th, 2023

World’s first logical quantum processor: Key step toward reliable quantum computing December 8th, 2023

Optical-fiber based single-photon light source at room temperature for next-generation quantum processing: Ytterbium-doped optical fibers are expected to pave the way for cost-effective quantum technologies November 3rd, 2023

Nanoelectronics

Interdisciplinary: Rice team tackles the future of semiconductors Multiferroics could be the key to ultralow-energy computing October 6th, 2023

Key element for a scalable quantum computer: Physicists from Forschungszentrum Jülich and RWTH Aachen University demonstrate electron transport on a quantum chip September 23rd, 2022

Reduced power consumption in semiconductor devices September 23rd, 2022

Atomic level deposition to extend Moore’s law and beyond July 15th, 2022

Discoveries

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Researchers’ approach may protect quantum computers from attacks March 8th, 2024

High-tech 'paint' could spare patients repeated surgeries March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Materials/Metamaterials/Magnetoresistance

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Focused ion beam technology: A single tool for a wide range of applications January 12th, 2024

Catalytic combo converts CO2 to solid carbon nanofibers: Tandem electrocatalytic-thermocatalytic conversion could help offset emissions of potent greenhouse gas by locking carbon away in a useful material January 12th, 2024

Announcements

What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

The Access to Advanced Health Institute receives up to $12.7 million to develop novel nanoalum adjuvant formulation for better protection against tuberculosis and pandemic influenza March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters

Researchers develop artificial building blocks of life March 8th, 2024

How surface roughness influences the adhesion of soft materials: Research team discovers universal mechanism that leads to adhesion hysteresis in soft materials March 8th, 2024

Curcumin nanoemulsion is tested for treatment of intestinal inflammation: A formulation developed by Brazilian researchers proved effective in tests involving mice March 8th, 2024

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Energy

Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024

Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023

Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023

The efficient perovskite cells with a structured anti-reflective layer – another step towards commercialization on a wider scale October 6th, 2023

Textiles/Clothing

This new fabric coating could drastically reduce microplastic pollution from washing clothes: University of Toronto Engineering researchers are working on a fabric finish to prevent microplastic fibres from shedding during laundry cycles January 27th, 2023

Protective equipment with graphene nanotubes meets the strictest ESD safety standards March 25th, 2022

Polymer fibers with graphene nanotubes make it possible to heat hard-to-reach, complex-shaped items February 11th, 2022

Flexible material shows potential for use in fabrics to heat, cool July 3rd, 2020

Photonics/Optics/Lasers

Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024

Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024

HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024

A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project