Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Band Gaps, Made to Order: Engineers create atomically thin superlattice materials with precision

This artist’s representation shows an electron beam (in purple) being used to create a 2D superlattice made up of quantum dots having extraordinary atomic-scale precision and placement.
Photo Credit: PETER ALLEN
This artist’s representation shows an electron beam (in purple) being used to create a 2D superlattice made up of quantum dots having extraordinary atomic-scale precision and placement. Photo Credit: PETER ALLEN

Abstract:
Control is a constant challenge for materials scientists, who are always seeking the perfect material — and the perfect way of treating it — to induce exactly the right electronic or optical activity required for a given application.

Band Gaps, Made to Order: Engineers create atomically thin superlattice materials with precision

Santa Barbara, CA | Posted on September 26th, 2017

One key challenge to modulating activity in a semiconductor is controlling its band gap. When a material is excited with energy, say, a light pulse, the wider its band gap, the shorter the wavelength of the light it emits. The narrower the band gap, the longer the wavelength.

As electronics and the devices that incorporate them — smartphones, laptops and the like — have become smaller and smaller, the semiconductor transistors that power them have shrunk to the point of being not much larger than an atom. They can’t get much smaller. To overcome this limitation, researchers are seeking ways to harness the unique characteristics of nanoscale atomic cluster arrays — known as quantum dot superlattices — for building next generation electronics such as large-scale quantum information systems. In the quantum realm, precision is even more important.

New research conducted by UC Santa Barbara’s Department of Electrical and Computer Engineering reveals a major advance in precision superlattices materials. The findings by Professor Kaustav Banerjee, his Ph.D. students Xuejun Xie, Jiahao Kang and Wei Cao, postdoctoral fellow Jae Hwan Chu and collaborators at Rice University appear in the journal Nature Scientific Reports.

Their team’s research uses a focused electron beam to fabricate a large-scale quantum dot superlattice on which each quantum dot has a specific pre-determined size positioned at a precise location on an atomically thin sheet of two-dimensional (2-D) semiconductor molybdenum disulphide (MoS2). When the focused electron beam interacts with the MoS2 monolayer, it turns that area — which is on the order of a nanometer in diameter — from semiconducting to metallic. The quantum dots can be placed less than four nanometers apart, so that they become an artificial crystal — essentially a new 2-D material where the band gap can be specified to order, from 1.8 to 1.4 electron volts (eV).

This is the first time that scientists have created a large-area 2-D superlattice — nanoscale atomic clusters in an ordered grid — on an atomically thin material on which both the size and location of quantum dots are precisely controlled. The process not only creates several quantum dots, but can also be applied directly to large-scale fabrication of 2-D quantum dot superlattices. “We can, therefore, change the overall properties of the 2-D crystal,” Banerjee said.

Each quantum dot acts as a quantum well, where electron-hole activity occurs, and all of the dots in the grid are close enough to each other to ensure interactions. The researchers can vary the spacing and size of the dots to vary the band gap, which determines the wavelength of light it emits.

“Using this technique, we can engineer the band gap to match the application,” Banerjee said. Quantum dot superlattices have been widely investigated for creating materials with tunable band gaps but all were made using “bottom-up” methods in which atoms naturally and spontaneously combine to form a macro-object. But those methods make it inherently difficult to design the lattice structure as desired and, thus, to achieve optimal performance.

As an example, depending on conditions, combining carbon atoms yields only two results in the bulk (or 3-D) form: graphite or diamond. These cannot be ‘tuned’ and so cannot make anything in between. But when atoms can be precisely positioned, the material can be designed with desired characteristics.

“Our approach overcomes the problems of randomness and proximity, enabling control of the band gap and all the other characteristics you might want the material to have — with a high level of precision,” Xie said. “This is a new way to make materials, and it will have many uses, particularly in quantum computing and communication applications. The dots on the superlattice are so close to each other that the electrons are coupled, an important requirement for quantum computing.”

The quantum dot is theoretically an artificial “atom.” The developed technique makes such design and “tuning” possible by enabling top-down control of the size and the position of the artificial atoms at large scale.

To demonstrate the level of control achieved, the authors produced an image of “UCSB” spelled out in a grid of quantum dots. By using different doses from the electron beam, they were able to cause different areas of the university’s initials to light up at different wavelengths.

“When you change the dose of the electron beam, you can change the size of the quantum dot in the local region, and once you do that, you can control the band gap of the 2-D material,” Banerjee explained. “If you say you want a band gap of 1.6 eV, I can give it to you. If you want 1.5 eV, I can do that, too, starting with the same material.”

This demonstration of tunable direct band gap could usher a new generation of light-emitting devices for photonics applications.

####

For more information, please click here

Contacts:
James Badham

(805) 893-3648

Julie Cohen

(805) 893-7220

Copyright © University of California, Santa Barbara

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 News Press

News and information

A new 'spin' on kagome lattices: Team's findings shed new light on the presence of spin-orbit coupling and topological spin textures in kagome lattices December 9th, 2018

Milestone for bERLinPro: Photocathodes with high quantum efficiency December 8th, 2018

Harnessing the power of 'spin orbit' coupling in silicon: Scaling up quantum computation December 7th, 2018

180 Degree Capital Corp.’s Portfolio Company, TheStreet, Inc., Agrees to Sell Its Institutional Business Units to Euromoney Institutional Investor PLC for $87.3 Million December 6th, 2018

Possible Futures

A new 'spin' on kagome lattices: Team's findings shed new light on the presence of spin-orbit coupling and topological spin textures in kagome lattices December 9th, 2018

Milestone for bERLinPro: Photocathodes with high quantum efficiency December 8th, 2018

Harnessing the power of 'spin orbit' coupling in silicon: Scaling up quantum computation December 7th, 2018

CEA-Leti’s RRAM-based TCAM Circuits Meet Requirements of Multicore Neuromorphic Processors December 5th, 2018

Chip Technology

A new 'spin' on kagome lattices: Team's findings shed new light on the presence of spin-orbit coupling and topological spin textures in kagome lattices December 9th, 2018

Harnessing the power of 'spin orbit' coupling in silicon: Scaling up quantum computation December 7th, 2018

CEA-Leti’s RRAM-based TCAM Circuits Meet Requirements of Multicore Neuromorphic Processors December 5th, 2018

Nanoscribe Presents Successor Model Photonic Professional GT2 for High-Resolution 3D Microfabrication: The first ever production of structures in millimeter size with micrometer precision December 4th, 2018

Optical computing/Photonic computing

An important step towards completely secure quantum communication networks November 30th, 2018

Bending light around tight corners without backscattering losses: New photonic crystal waveguide based on topological insulators paves the way to build futuristic light-based computers November 19th, 2018

GaN Rising: UC Santa Barbara electrical and computer engineering professor Umesh Mishra to deliver 63rd Annual Faculty Research Lecture November 16th, 2018

AIM Photonics Members Meeting Provides Key Updates on the Initiative’s Progress: Day-Long Engagement in Syracuse, NY, Sees Strong Attendance and Interest from Industry, Government, and Academic Partners November 2nd, 2018

Nanoelectronics

2-D magnetism: Atom-thick platforms for energy, information and computing research: Scientists say the tiny 'spins' of electrons show potential to one day support next-generation innovations in many fields October 31st, 2018

Machine learning helps improving photonic applications September 28th, 2018

How a tetrahedral substance can be more symmetrical than a spherical atom: A new type of symmetry September 14th, 2018

Laser sintering optimized for printed electronics: New study sheds (laser) light on the best means of laying down thin-film circuitry September 13th, 2018

Discoveries

A new 'spin' on kagome lattices: Team's findings shed new light on the presence of spin-orbit coupling and topological spin textures in kagome lattices December 9th, 2018

Milestone for bERLinPro: Photocathodes with high quantum efficiency December 8th, 2018

Harnessing the power of 'spin orbit' coupling in silicon: Scaling up quantum computation December 7th, 2018

Iran Develops Water-Repellent Nano-Paint December 5th, 2018

Announcements

A new 'spin' on kagome lattices: Team's findings shed new light on the presence of spin-orbit coupling and topological spin textures in kagome lattices December 9th, 2018

Milestone for bERLinPro: Photocathodes with high quantum efficiency December 8th, 2018

Harnessing the power of 'spin orbit' coupling in silicon: Scaling up quantum computation December 7th, 2018

180 Degree Capital Corp.’s Portfolio Company, TheStreet, Inc., Agrees to Sell Its Institutional Business Units to Euromoney Institutional Investor PLC for $87.3 Million December 6th, 2018

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

A new 'spin' on kagome lattices: Team's findings shed new light on the presence of spin-orbit coupling and topological spin textures in kagome lattices December 9th, 2018

Milestone for bERLinPro: Photocathodes with high quantum efficiency December 8th, 2018

Harnessing the power of 'spin orbit' coupling in silicon: Scaling up quantum computation December 7th, 2018

New research could fine-tune the gene scissors CRISPR December 1st, 2018

Tools

Milestone for bERLinPro: Photocathodes with high quantum efficiency December 8th, 2018

Spectradyne Partners with Particle Technology Labs for Measurement Services December 6th, 2018

Nanoscribe Presents Successor Model Photonic Professional GT2 for High-Resolution 3D Microfabrication: The first ever production of structures in millimeter size with micrometer precision December 4th, 2018

CEA-Leti and Silvaco to Develop GAA SPICE Compact Models for Circuit Design and Technology Co-optimization: Project Combines CEA-Leti’s Compact Modeling Expertise And Silvaco’s Extensive Experience in SPICE Compact Model Integration and Extraction December 3rd, 2018

Quantum Dots/Rods

Machine learning helps improving photonic applications September 28th, 2018

A Novel Graphene Quantum Dot Structure Takes the Cake August 24th, 2018

Individual quantum dots imaged in 3-D for first time February 28th, 2018

Moving nanoparticles using light and magnetic fields January 25th, 2018

Photonics/Optics/Lasers

Nanoscribe Presents Successor Model Photonic Professional GT2 for High-Resolution 3D Microfabrication: The first ever production of structures in millimeter size with micrometer precision December 4th, 2018

CEA-Leti Extends 300mm Line and Adds Avenues for Developing Disruptive Technologies: Execution Relies on CEA-Leti’s Fully Implemented Technology With Module-Level Innovations & Devices and Their Architectures December 3rd, 2018

Bending light around tight corners without backscattering losses: New photonic crystal waveguide based on topological insulators paves the way to build futuristic light-based computers November 19th, 2018

GaN Rising: UC Santa Barbara electrical and computer engineering professor Umesh Mishra to deliver 63rd Annual Faculty Research Lecture November 16th, 2018

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