Search
Menu
Deposition Sciences Inc. - Difficult Coatings - LB - 8/23

Researchers Probe Graphene Alternatives with SHG

Facebook X LinkedIn Email
BERKELEY, Calif., May 7, 2014 — Scientists have a new way to study the optical and electrical properties of 2-D metals that could compete with graphene in semiconductor and other applications.


A new SHG imaging technique allows rapid and all-optical determination of the crystal orientations of 2-D semiconductor membranes at a large scale, providing the knowledge needed to use these materials in nanoelectronic devices. Images courtesy of Lawrence Berkeley National Laboratory.


Using ultrafast IR pulses, researchers with the Lawrence Berkeley National Laboratory observed strong nonlinear optical resonance along the edges of a single layer of molybdenum disulfide (MoS2).

“We … discovered extraordinary second-harmonic light-generation properties that may be used for the in situ monitoring of electronic changes and chemical reactions that occur at the one-dimensional atomic edges,” said Xiang Zhang, a Berkeley Lab faculty scientist.

MoS2 and other transition metal dichalcogenides feature the same flat, hexagonal structure as graphene and many of the same electrical advantages but, unlike graphene, have direct energy bandgaps. This facilitates their application in transistors and other electronic devices, particularly light-emitting diodes.



Gentec Electro-Optics Inc   - Measure Your Laser MR
(A) Optical image of a large area of monolayer MoS2 and (B) an SHG image of the same area revealing grains and grain boundaries where translational symmetry is broken to form 1-D edge states.


Until now, observation of dichalcogenides had been limited to scanning tunneling and transition electron microscopes. Discovering the visible SHG properties of MoS2 allowed researchers to easily capture the crystal structures and grain orientations with an optical microscope.

“Our nonlinear optical imaging technique is a noninvasive, fast, easy metrologic approach to the study of 2-D atomic materials,” said Xiaobo Yin, a former member of Zhang’s research group now at the University of Colorado, Boulder. “We don’t need to prepare the sample on any special substrate or vacuum environment, and the measurement won’t perturb the sample during the imaging process.”

Transition metal dichalcogenides could also serve as catalysts for hydrogen evolution reaction in fuel cells, desulfurization and other chemical reactions, researchers said.

The research was supported by the US Department of Energy Office of Science and by the US Air Force Office of Scientific Research Multidisciplinary University Research Initiative. It is published in Science (doi: 10.1126/science.1250564).

Published: May 2014
Glossary
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
second-harmonic generation
Second-harmonic generation (SHG) is a nonlinear optical process that occurs when two photons with the same frequency combine within a nonlinear material, resulting in the generation of a new photon with twice the frequency (and therefore half the wavelength) of the original photons. This phenomenon is a specific case of second-order nonlinear optical effects. Key points about second-harmonic generation include: Nonlinear optical process: SHG is a nonlinear optical effect, meaning that the...
AmericasenergygrapheneLawrence Berkeley National LaboratoryMaterialsMicroscopymolybdenum sulfidenanoOpticsResearch & Technologysecond-harmonic generationSHGXiang ZhangXiaobo Yintransition metal dichalcogenide

We use cookies to improve user experience and analyze our website traffic as stated in our Privacy Policy. By using this website, you agree to the use of cookies unless you have disabled them.