Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Clear Picture Of 'Birth' Of Semiconductor Nanostructures

Abstract:
Information will help researchers better understand and use materials that could lead to small, efficient and powerful computers, communication devices and scientific instruments.

Researchers Develop Clear Picture Of 'Birth' Of Semiconductor Nanostructures

Fayetteville, AR | April 04, 2005

University of Arkansas researchers have witnessed the birth of a quantum dot and learned more about how such atomic islands form and grow, using the ultrahigh vacuum facility on campus. This information will help researchers better understand and use materials that could lead to small, efficient and powerful computers, communication devices and scientific instruments.

Seongho Cho, Zhiming Wang, and Gregory Salamo report their findings in the upcoming issue of the journal Applied Physics Letters.

"We have changed the way people have to think about how nanostructures grow on a surface," said Salamo, University Professor of physics. "People had a different idea of how these islands formed, but until now there was not direct evidence."

The researchers combined the molecular-beam epitaxy machine, which creates material atom by atom, with scanning tunneling microscopy, which can observe the atoms, to witness the creation of quantum dots, or atomic islands, of indium gallium arsenide (InGaAs) atoms atop a gallium arsenide (GaAs) surface. InGaAs is a material of electronic and optical interest for properties that could enhance communications equipment, computers and electronics.

At the atomic level, a surface is characterized by small monolayer "steps." Until now, researchers believed that the first atom of a quantum dot would land at the base of the step, rather than further out towards the edge of the step. The work of Cho, Wang and Salamo shows instead that the first atom lands at the step's edge.

"An island growing from below the step edge must first build up to a height equal to the step. This is unnecessary since it could more easily just start from the top of the step," said Wang, a research professor working with Salamo.

The researchers found that the first atoms of InGaAs land side by side atop the GaAs surface and experience a strain, much like a person trying to squeeze into an already crowded line. Therefore, after a short time, it becomes easier for an InGaAs atom to land atop other InGaAs atoms instead of on the initial surface. Also, fewer atoms land on a layer as the layers build up, allowing the atoms to have more space and experience less strain. The researchers witnessed this sequential, upward, narrowing growth as they studied the formation of the InGaAs quantum dots, which ended by forming a pyramid-like structure.

This observation also is significant because it may offer a more general explanation of how other semiconductor materials behave at the nanoscale, Wang said.

"It was predicted by previous theory independent of materials, but wasn't observed for InGaAs islands before," he said.

"We do not yet have a complete picture of how these quantum dots grow," Salamo said. "But we have added to the picture."

This picture has implications that extend beyond semiconductors, he added.

"How these small structures grow and how they behave tells us about the rules that govern small structures in general," Salamo said. "Cells are small. DNA is small. Everything is composed of small structures. When you understand how things go together, they supply a library for looking at other things in science."

####



Contact:
Zhiming M. Wang
Research professor of microelectronics-photonics
(479) 575-4217
zmwang@uark.edu

Gregory J. Salamo
University Professor of physics
Fulbright College
(479) 575-5931
salamo@uark.edu

Melissa Lutz Blouin
Science and research communications manager
(479) 575-5555
blouin@uark.edu

Copyright University of Arkansas

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

Possible Futures

Laser activated gold pyramids could deliver drugs, DNA into cells without harm: Microstructures create temporary pores in cells March 27th, 2017

Researchers make flexible glass for tiny medical devices: Glass can bend over and over again on a nanoscale March 27th, 2017

Cryo-electron microscopy achieves unprecedented resolution using new computational methods March 25th, 2017

Argon is not the 'dope' for metallic hydrogen March 24th, 2017

Nanoelectronics

Scientists discover new 'boat' form of promising semiconductor: GeSe Uncommon form attenuates semiconductor's band gap size March 23rd, 2017

UC researchers use gold coating to control luminescence of nanowires: University of Cincinnati physicists manipulate nanowire semiconductors in pursuit of making electronics smaller, faster and cheaper March 17th, 2017

A SOI wafer is a suitable substrate for gallium nitride crystals: Improved characteristics in power electronics and radio applications can be achieved by using a SOI wafer for gallium nitride growth March 4th, 2017

Smart multi-layered magnetic material acts as an electric switch: New study reveals characteristic of islands of magnetic metals between vacuum gaps, displaying tunnelling electric current March 1st, 2017

Discoveries

Laser activated gold pyramids could deliver drugs, DNA into cells without harm: Microstructures create temporary pores in cells March 27th, 2017

Researchers make flexible glass for tiny medical devices: Glass can bend over and over again on a nanoscale March 27th, 2017

Cryo-electron microscopy achieves unprecedented resolution using new computational methods March 25th, 2017

Argon is not the 'dope' for metallic hydrogen March 24th, 2017

Materials/Metamaterials

Researchers make flexible glass for tiny medical devices: Glass can bend over and over again on a nanoscale March 27th, 2017

Argon is not the 'dope' for metallic hydrogen March 24th, 2017

Promising results obtained with a new electrocatalyst that reduces the need for platinum: Researchers from Aalto University have succeeded in manufacturing electrocatalysts used for storing electric energy with one-hundredth of the amount of platinum that is usually needed March 24th, 2017

Rice U. refines filters for greener natural gas: New study defines best materials for carbon capture, methane selectivity March 23rd, 2017

Announcements

Laser activated gold pyramids could deliver drugs, DNA into cells without harm: Microstructures create temporary pores in cells March 27th, 2017

Researchers make flexible glass for tiny medical devices: Glass can bend over and over again on a nanoscale March 27th, 2017

Cryo-electron microscopy achieves unprecedented resolution using new computational methods March 25th, 2017

Argon is not the 'dope' for metallic hydrogen March 24th, 2017

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



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project