Navigation Links
Dreidel-like dislocations lead to remarkable properties
Date:12/14/2012

HOUSTON (Dec. 14, 2012) A new material structure predicted at Rice University offers the tantalizing possibility of a signal path smaller than the nanowires for advanced electronics now under development at Rice and elsewhere.

Theoretical physicist Boris Yakobson and postdoctoral fellow Xiaolong Zou were investigating the atomic-scale properties of two-dimensional materials when they found to their surprise that a particular formation, a grain boundary in metal disulfides, creates a metallic and therefore conducting path only a fraction of a nanometer wide.

That's basically the width of a chain of atoms, Yakobson said.

The discovery reported this week in the American Chemical Society journal Nano Letters sprang from an investigation of how atoms energetically relate to each other and form topological defects in two-dimensional semiconductors. In recent work, Yakobson's group has analyzed defects in graphene, the single-atom sheet of carbon that is under intense scrutiny by labs around the world.

But flat graphene has no band gap; electrons flow straight through. "There is a lot of effort to open a gap in graphene, but this is not easy," said Yakobson, Rice's Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and professor of chemistry. "People are trying different ways, but none of them are straightforward. This motivated the search for other two-dimensional materials."

Molybdenum/sulfur (or tungsten/sulfur) materials are becoming interesting to scientists because they have a useful natural band gap, about two electron volts in the case of molybdenum/sulfur. And while they are technically two-dimensional materials, the energies at play force their atoms into a staggered arrangement.

"It's more complex than graphene," Yakobson said. "There's a layer of metal in the middle, with sulfur atoms above and below, but they're fully connected by covalent bonds in a honeycomb lattice, so it's one compound."

Chemical vapor deposition is typically used to grow such material; under high temperatures the atoms (like carbon for graphene) fall into line and form sheets. But when two such blooms appear and they meet, they don't necessarily line up. Where they merge, they form what are called "grain boundaries," akin to grains in wood that join at awkward angles. (Think of a branch meeting a tree trunk.) Those grain boundaries affect the electrical properties of the merged material.

Zou calculated those properties based on the atomic energies of the elements. In looking at the elemental bonds, the researchers found the expected "dislocations" where the energies force atoms out of their regular patterns. "Where the sheets meet, they cannot have an ideal lattice structure, so they have these stitches, the dislocations. Each grain boundary is just a series of these dislocations," Yakobson said.

It was only coincidence that the dislocations took on dreidel-like shapes for a paper published during Hanukkah, he said.

"We found order in this complexity and chaos, the exact structures that are possible at the grain boundaries and the dislocations types," he said.

The growing molybdenum/sulfur sheets can meet at any angle, and though the sheets are semiconducting, the boundaries between them generally stop electrical signals in their tracks. But at one particular angle -- 60 degrees -- the periodic dislocations are close enough to pass signals on from one to the next along the length of the boundary. "Basically, they're metallic in this direction," Yakobson said.

"So in the middle of these domains of semiconducting material, you have this boundary line that carries current in one direction, like a wire. And it's only a few angstroms wide," he said.

"Metal disulfides may be promising for future electronic devices based on materials with reduced dimensions," Zou said. "It is important to understand the effects of topological defects on the electronic properties as we push toward post-silicon devices."


'/>"/>

Contact: David Ruth
david@rice.edu
713-348-6327
Rice University
Source:Eurekalert  

Related biology technology :

1. Waterfront Properties Proud To Have Prestigious Max Planck Society in its Back Yard
2. Unique properties of graphene lead to a new paradigm for low-power telecommunications
3. Discovery of material with amazing properties
4. Physical properties predict stem cell outcome
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Dreidel-like dislocations lead to remarkable properties
(Date:10/11/2017)... ... October 11, 2017 , ... Proscia Inc ., a ... Webinar titled, “Pathology is going digital. Is your lab ready?” with Dr. Nicolas ... practices and how Proscia improves lab economics and realizes an increase in diagnostic ...
(Date:10/11/2017)... ... October 11, 2017 , ... Disappearing forests and increased ... of over 5.5 million people each year. Especially those living in larger cities are ... - based in one of the most pollution-affected countries globally - decided to take ...
(Date:10/10/2017)... ... ... San Diego-based team building and cooking events company, Lajollacooks4u, has unveiled a ... new look is part of a transformation to increase awareness, appeal to new markets ... It will also expand its service offering from its signature gourmet cooking classes and ...
(Date:10/10/2017)... , ... October 10, 2017 , ... Dr. Bob Harman, ... his local San Diego Rotary Club. The event entitled “Stem Cells ... and had 300+ attendees. Dr. Harman, DVM, MPVM was joined by two human ...
Breaking Biology Technology:
(Date:5/16/2017)... , May 16, 2017  Veratad Technologies, LLC ... of online age and identity verification solutions, announced today ... Identity Conference 2017, May 15 thru May 17, 2017, ... Building and International Trade Center. Identity ... globe and in today,s quickly evolving digital world, defining ...
(Date:4/18/2017)... Calif. , April 18, 2017  Socionext Inc., a global ... of a media edge server, the M820, which features the company,s ... recognition software provided by Tera Probe, Inc., will be showcased during ... at the NAB show at the Las Vegas ... ...
(Date:4/11/2017)... 11, 2017 Research and Markets has announced ... report to their offering. ... global eye tracking market to grow at a CAGR of 30.37% ... Tracking Market 2017-2021, has been prepared based on an in-depth market ... landscape and its growth prospects over the coming years. The report ...
Breaking Biology News(10 mins):