Graphene is nature's thinnest elastic material and displays exceptional mechanical and electronic properties. Its one-atom thickness, planar geometry, high current-carrying capacity and thermal conductivity make it ideally suited for further miniaturizing electronics through ultra-small devices and components for semiconductor circuits and computers.
But one of graphene's intrinsic features is ripples, similar to those seen on plastic wrap tightly pulled over a clamped edge. Induced by pre-existing strains in graphene, these ripples can strongly affect graphene's electronic properties, and not always favorably.
If the ripples can be controlled, however, they can be used to advantage in nanoscale devices and electronics, opening up a new arena in graphene engineering: strain-based devices.
The unusual thermal contraction of graphene had been predicted theoretically, but Lau's lab is the first to demonstrate and quantify the phenomenon experimentally.
Study results appear July 26 in the advance online publication of Nature Nanotechnology.
Because graphene is both an excellent conductor and the thinnest elastic membrane, the ripples could have profound implications for graphene-based electronics.
"This is because graphene's ability to conduct electricity is expected to vary with the local shape of the membrane," Lau said. "For instance, the ripples may produce effective magnetic fields that can be used to steer and manipulate electrons in a nanoscale device without an external magnet."
Lau, an associate professor of physics and a member of UCR's Center for Nanoscale Science and Engineering, and her colleagues examined the ripples' morphology using a scanning electron microscope and an atomic force microscope. They found that almost all the graphene membranes underwent dramatic morphological changes when heated, displaying significant alterations in the ripple geometry, a buckling of the graphene membrane, or both.
Their experimental system, which involved a stage inside a scanning electron microscope (SEM) with a built-in heater, thermometer and several electrical feed-throughs, enabled them to image graphene while it was being heated and explore the interplay between graphene's mechanical, thermal and electrical properties.
"Our result has important implications for controlling thermally induced stress in graphene electronics," Lau said. "Our ability to control and manipulate the ripples in graphene sheets represents the first step towards strain-based graphene engineering. We show that suspended graphene is almost invariably rippled, and this may need to be considered in the interpretation of a broad array of existing and future research."
Proposed to supplement or replace silicon as the main electronic material, graphene is a single layer of graphite. Even though graphite has been studied for decades, the single sheet first was isolated experimentally only in 2004. Graphene's structure is a two-dimensional honeycomb lattice of carbon atoms. Structurally, it is related to carbon nanotubes (tiny hollow tubes formed by rolling up sheets of graphene) and buckyballs (hollow carbon molecules that form a closed cage).
Lau, who earlier this month was named one of the recipients of the Presidential Early Career Awards for Scientists and Engineers for the 2008 competition, joined UCR in 2004. She was joined in the 18-month study by UCR's Wenzhong Bao (first author), Feng Miao, Zhen Chen, Hang Zhang, Wanyoung Jang and Chris Dames.
The research was supported in part by grants from the National Science Foundation and the Office of Naval Research.
The University of California, Riverside is a doctoral research university, a living laboratory for groundbreaking exploration of issues critical to Inland Southern California, the state and communities around the world. Reflecting California's diverse culture, UCR's enrollment of about 17,000 is expected to grow to 21,000 students by 2020. The campus is planning a medical school and has reached the heart of the Coachella Valley by way of the UCR Palm Desert Graduate Center. The campus has an annual statewide economic impact of more than $1 billion. To learn more, visit www.ucr.edu or call (951) UCR-NEWS.
Iqbal Pittalwala | EurekAlert!
Laser sensor LAH-G1 - optical distance sensors with measurement value display
15.08.2017 | WayCon Positionsmesstechnik GmbH
Engineers find better way to detect nanoparticles
14.08.2017 | Washington University in St. Louis
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy