Google Play icon

Sharp meets flat in tunable 2D material

Share
Posted August 13, 2019

A Rice University lab wants its products to look sharp, even at the nanoscale. Its latest creation is right on target.

The Rice lab of materials scientist Pulickel Ajayan has created unique two-dimensional flakes with two distinct personalities: molybdenum diselenide on one side of a sharp divide with rhenium diselenide on the other.

Adjacent crystal structures of rhenium diselenide (top) and molybdenum diselenide form a 2D transition metal dichalcogenide heterostructure with sharply separated domains. The unique material created at Rice University shows promise for optoelectronic applications. Image credit: Center for Nanophase Materials Science and the Ajayan Research Group

From all appearances, the two-toned material likes it that way, growing naturally — though under tight conditions — in a chemical vapor deposition furnace.

The material is a 2D transition metal dichalcogenide heterostructure, a crystal with more than one chemical component. That’s not unusual in itself, but the sharp zigzag boundary between elements in the material reported in the American Chemical Society journal Nano Letters is unique.

Dichalcogenides are semiconductors that incorporate transition metals and chalcogens. They’re a promising component for optoelectronic applications like solar cells, photodetectors and sensing devices. Lead author Amey Apte, a Rice graduate student, said they may also be suitable materials for quantum computing or neuromorphic computing, which emulates the structure of the human brain.

Apte said well-known, atomically flat molybdenum-tungsten dichalcogenide heterostructures can be more alloy-like, with diffuse boundaries between their crystal domains. However, the new material — technically, 2H MoSe2-1T’ ReSe2 — has atomically sharp interfaces that gives it a smaller electronic band gap than other dichalcogenides.

“Instead of having one unique band gap based on the composition of an alloy, we can tune the band gap in this material in a very controllable way,” Apte said. “The strong dissimilarity between two adjacent atomically thin domains opens up new avenues.” He said the range of voltages likely spans from 1.5 to 2.5 electron volts.

Growing the materials reliably involved the creation of a phase diagram that laid out how each parameter — the balance of chemical gas precursor, the temperature and the time — affects the process. Rice graduate student and co-author Sandhya Susarla said the diagram serves as a road map for manufacturers.

An illustration shows several arrangements of rhenium diselenide and molybdenum diselenide, which form a razor-sharp junction where they meet in a new transition metal dichalcogenide created at Rice University. Click on the image for a larger version. Image credit: Ajayan Research Group

“The biggest issue in these 2D materials has been that they’re not very reproducible,” she said. “They’re very sensitive to a lot of parameters, because the process is kinetically controlled.

“But our process is scalable because it’s thermodynamically controlled,” Susarla said. “Manufacturers don’t have a lot of parameters to look at. They just have to look at the phase diagram, control the composition and they will get the product every time.”

The researchers think they can gain further control of the material’s form by tailoring the substrate for epitaxial growth. Having the atoms fall into place in accordance with the surface’s own atomic arrangement would allow for far more customization.

Source: Rice University

Featured news from related categories:

Technology Org App
Google Play icon
85,613 science & technology articles

Most Popular Articles

  1. New treatment may reverse celiac disease (October 22, 2019)
  2. The World's Energy Storage Powerhouse (November 1, 2019)
  3. Universe is a Sphere and Not Flat After All According to a New Research (November 7, 2019)
  4. "Helical Engine" Proposed by NASA Engineer could Reach 99% the Speed of Light. But could it, really? (October 17, 2019)
  5. ‘Artificial leaf’ successfully produces clean gas (October 22, 2019)

Follow us

Facebook   Twitter   Pinterest   Tumblr   RSS   Newsletter via Email