Navigation Links
Graphene films clear major fabrication hurdle

Graphene, the two-dimensional crystalline form of carbon, is a potential superstar for the electronics industry. With freakishly mobile electrons that can blaze through the material at nearly the speed of light 100 times faster than electrons can move through silicon graphene could be used to make superfast transistors or computer memory chips. Graphene's unique "chicken wire" atomic structure exhibits incredible flexibility and mechanical strength, as well as unusual optical properties that could open a number of promising doors in both the electronics and the photonics industries. However, among the hurdles preventing graphite from joining the pantheon of star high-tech materials, perhaps none looms larger than just learning to make the stuff in high quality and usable quantities.

"Before we can fully utilize the superior electronic properties of graphene in devices, we must first develop a method of forming uniform single-layer graphene films on nonconducting substrates on a large scale," says Yuegang Zhang, a materials scientist with the Lawrence Berkeley National Laboratory (Berkeley Lab). Current fabrication methods based on mechanical cleavage or ultrahigh vacuum annealing, he says, are ill-suited for commercial-scale production. Graphene films made via solution-based deposition and chemical reduction have suffered from poor or uneven quality.

Zhang and colleagues at Berkeley Lab's Molecular Foundry, a U.S. Department of Energy (DOE) center for nanoscience, have taken a significant step at clearing this major hurdle. They have successfully used direct chemical vapor deposition (CVD) to synthesize single-layer films of graphene on a dielectric substrate. Zhang and his colleagues made their graphene films by catalytically decomposing hydrocarbon precursors over thin films of copper that had been pre-deposited on the dielectric substrate. The copper films subsequently dewetted (separated into puddles or droplets) and were evaporated. The final product was a single-layer graphene film on a bare dielectric.

"This is exciting news for electronic applications because chemical vapor deposition is a technique already widely used in the semiconductor industry," Zhang says. "Also, we can learn more about the growth of graphene on metal catalyst surfaces by observing the evolution of the films after the evaporation of the copper. This should lay an important foundation for further control of the process and enable us to tailor the properties of these films or produce desired morphologies, such as graphene nanoribbons."

Zhang and his colleagues have reported their findings in the journal Nano Letters in a paper titled, "Direct Chemical Vapor Deposition of Graphene on Dielectric Surfaces." Other co-authors of this paper were Ariel Ismach, Clara Druzgalski, Samuel Penwell, Maxwell Zheng, Ali Javey and Jeffrey Bokor, all with Berkeley Lab.

In their study, Zhang and his colleagues used electron-beam evaporation to deposit copper films ranging in thickness from 100 to 450 nanometers. Copper was chosen because as a low carbon solubility metal catalyst it was expected to allow better control over the number of graphene layers produced. Several different dielectric substrates were evaluated including single-crystal quartz, sapphire, fused silica and silicon oxide wafers. CVD of the graphene was carried out at 1,000 degrees Celsius in durations that ranged from 15 minutes up to seven hours.

"This was done to allow us to study the effect of film thickness, substrate type and CVD growth time on the graphene formation," Zhang says.

A combination of scanning Raman mapping and spectroscopy, plus scanning electron and atomic force microscopy confirmed the presence of continuous single-layer graphene films coating metal-free areas of dielectric substrate measuring tens of square micrometers.

"Further improvement on the control of the dewetting and evaporation process could lead to the direct deposition of patterned graphene for large-scale electronic device fabrication, Zhang says. "This method could also be generalized and used to deposit other two-dimensional materials, such as boron-nitride."

Even the appearance of wrinkles in the graphene films that followed along the lines of the dewetting shape of the copper could prove to be beneficial in the long-run. Although previous studies have indicated that wrinkles in a graphene film have a negative impact on electronic properties by introducing strains that reduce electron mobility, Zhang believes the wrinkles can be turned to an advantage.

"If we can learn to control the formation of wrinkles in our films, we should be able to modulate the resulting strain and thereby tailor electronic properties," he says. "Further study of the wrinkle formation could also give us important new clues for the formation of graphene nanoribbons."


Contact: Lynn Yarris
DOE/Lawrence Berkeley National Laboratory

Related biology technology :

1. UM physicists show electrons can travel over 100 times faster in graphene than in silicon
2. Graphene gazing gives glimpse of foundations of universe
3. Graphene used to create worlds smallest transistor
4. Graphene-based gadgets may be just years away
5. By adding graphene, researchers create superior polymer
6. Penn scientists demonstrate potential of graphene films as next-generation transistors
7. Graphene pioneers follow in Nobel footsteps
8. New graphene-based material clarifies graphite oxide chemistry
9. Researchers discover method for mass production of nanomaterial graphene
10. Light-speed nanotech: Controlling the nature of graphene
11. Scientists prove graphenes edge structure affects electronic properties
Post Your Comments:
Related Image:
Graphene films clear major fabrication hurdle
(Date:10/12/2015)... Oct. 12, 2015 This report covers the ... cell type, products, applications, end-user markets and geographic segmentation. ... The global cell expansion market generated revenue of ... reach revenues of $9.7 billion in 2015 and $22.0 ... (CAGR) of 17.8% from 2015 to 2020. This ...
(Date:10/12/2015)... cell surface marker detection market ... to a new report by Grand View Research, Inc. This ... of oncology diseases and other cell-associated disorders. --> ... USD 6.49 billion by 2022, according to a new report ... be attributed to rise in incidence of oncology diseases and ...
(Date:10/12/2015)... CITY , Oct. 12, 2015 /PRNewswire/ - Aeterna ... specialty biopharmaceutical company engaged in developing and commercializing novel ... the departure of Dennis Turpin , the Company,s ... decision to close its Quebec City ... Chairman, President and Chief Executive Officer of the Company ...
(Date:10/12/2015)... , October 12, 2015 LabStyle ... Diabetes Management Solution, today announced its Medical Director, Dr. ... study at MobiHealth,s 5th EAI International Conference on ... healthcare through innovations in mobile and wireless technologies," the ... from October 14 - 16, 2015. The ...
Breaking Biology Technology:
(Date:10/1/2015)... 2015  Biometrics includes diverse set of technologies ... such as fingerprints, eye retinas, facial patterns, voice ... technology has been constantly increasing in ... In addition to the most prominent popular method ... means of biometric authentication are rapidly gaining traction ...
(Date:9/30/2015)... PALM BEACH GARDENS, Fla. , Sept. 30, 2015 ... Circuit earlier this month issued another key ruling in ... Commission,s (ITC,s) determination that Korean fingerprint scanner company Suprema ... the Tariff Act of 1930, a trade provision that ... connection with import trade, by infringing two of Crossmatch,s ...
(Date:9/29/2015)... , Sept. 29, 2015 News ... productivity while also saving energy , Minimized design ... Low Power Active Mode and embedded Fujitsu PalmSecure authentication ... Fujitsu today shows that good things come ... refreshed models to its enterprise desktop and mobile portfolio. ...
Breaking Biology News(10 mins):