Cool nanotech image — graphene

Actually the accompanying article is pretty cool, too, so do take the time to check it out.

But now, the image …

This image of a single suspended sheet of graphene taken with the TEAM 0.5, at Berkeley Lab’s National Center for Electron Microscopy shows individual carbon atoms (yellow) on the honeycomb lattice.

Also from the link:

In the current study, the team made graphene nanoribbons using a nanowire mask-based fabrication technique. By measuring the conductance fluctuation, or ‘noise’ of electrons in graphene nanoribbons, the researchers directly probed the effect of quantum confinement in these structures. Their findings map the electronic band structure of these graphene nanoribbons using a robust electrical probing method. This method can be further applied to a wide array of nanoscale materials, including graphene-based electronic devices.

“It amazes us to observe such a clear correlation between the noise and the band structure of these graphene nanomaterials,” says lead author Guangyu Xu, a physicist at University of California, Los Angeles. “This work adds strong support to the quasi-one-dimensional subband formation in graphene nanoribbons, in which our method turns out to be much more robust than conductance measurement.”

One more bit from the link, from the intro actually:

In last week’s announcement of the Nobel Prize in Physics, the Royal Swedish Academy of Sciences lauded graphene’s “exceptional properties that originate from the remarkable world of quantum physics.” If it weren’t hot enough before, this atomically thin sheet of carbon is now officially in the global spotlight.

So expect to hear a lot more about graphene in the coming months. Of course if you’re a regular reader of this blog, you’ve been getting a pretty steady (aside from the last month of light blogging) diet of graphene since almost day one (since February 2008 to be exact).

Graphene nanomesh may be the semiconductor solution

I’ve done tons of blogging on graphene and this news seems to be direct competition with this graphene news I covered about a week ago. The issue is turning graphene into a semiconductor to allow the material to eventually replace silicon in electronic devices. The last link up there goes to a post outlining the concept of using nanoribbons of graphene, the middle link goes to research claiming a “nanomesh” is a superior method of turning the carbon nanomaterial into a semiconductor.

The release:

New graphene ‘nanomesh’ could change the future of electronics

Graphene, a one-atom-thick layer of a carbon lattice with a honeycomb structure, has great potential for use in radios, computers, phones and other electronic devices. But applications have been stymied because the semi-metallic graphene, which has a zero band gap, does not function effectively as a semiconductor to amplify or switch electronic signals.

While cutting graphene sheets into nanoscale ribbons can open up a larger band gap and improve function, ‘nanoribbon’ devices often have limited driving currents, and practical devices would require the production of dense arrays of ordered nanoribbons — a process that so far has not been achieved or clearly conceptualized.

But Yu Huang, a professor of materials science and engineering at the UCLA Henry Samueli School of Engineering and Applied Science, and her research team, in collaboration with UCLA chemistry professor Xiangfeng Duan, may have found a new solution to the challenges of graphene.

In research to be published in the March issue of Nature Nanotechnology (currently available online), Huang’s team reveals the creation of a new graphene nanostructure called graphene nanomesh, or GNM. The new structure is able to open up a band gap in a large sheet of graphene to create a highly uniform, continuous semiconducting thin film that may be processed using standard planar semiconductor processing methods.

“The nanomeshes are prepared by punching a high-density array of nanoscale holes into a single or a few layers of graphene using a self-assembled block copolymer thin film as the mask template,” said Huang.

The nanomesh can have variable periodicities, defined as the distance between the centers of two neighboring nanoholes. Neck widths, the shortest distance between the edges of two neighboring holes, can be as low as 5 nanometers.

This ability to control nanomesh periodicity and neck width is very important for controlling electronic properties because charge transport properties are highly dependent on the width and the number of critical current pathways.

Using such nanomesh as the semiconducting channel, Huang and her team have demonstrated room-temperature transistors that can support currents nearly 100 times greater than individual graphene nanoribbon devices, but with a comparable on-off ratio. The on-off ratio is the ratio between the currents when a device is switched on or switched off. This usually reveals how effectively a transistor can be switched off and on.

The researchers have also shown that the on-off ratio can be tuned by varying the neck width.

“GNMs can address many of the critical challenges facing graphene, as well as bypass the most challenging assembly problems,” Huang said. “In conjunction with recent advances in the growth of graphene over a large-area substrate, this concept has the potential to enable a uniform, continuous semiconducting nanomesh thin film that can be used to fabricate integrated devices and circuits with desired device size and driving current.

“The concept of the GNM therefore points to a clear pathway towards practical application of graphene as a semiconductor material for future electronics. The unique structural and electronic characteristics of the GNMs may also open up exciting opportunities in highly sensitive biosensors and a new generation of spintronics, from magnetic sensing to storage,” she said.

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The study was funded in part by Huang’s UCLA Henry Samueli School of Engineering and Applied Science Fellowship.

The UCLA Henry Samueli School of Engineering and Applied Science, established in 1945, offers 28 academic and professional degree programs, including an interdepartmental graduate degree program in biomedical engineering. Ranked among the top 10 engineering schools at public universities nationwide, the school is home to seven multimillion-dollar interdisciplinary research centers in wireless sensor systems, nanotechnology, nanomanufacturing and nanoelectronics, all funded by federal and private agencies.

For more news, visit the UCLA Newsroom and follow us on Twitter.

April 2009 media tips from Oak Ridge National Laboratory

The latest story ideas coming out of Oak Ridge National Laboratory.

The release:

April 2009 Story Tips

Story ideas from the Department of Energy’s Oak Ridge National Laboratory.

Sensors—Math to the rescue . . .

Making sense of the enormous amounts of information delivered by all types of sensors is an incredible challenge, but it’s being met head on with knowledge discovery techniques developed at Oak Ridge National Laboratory. Some of the strategies and approaches are outlined in a recently published book, “Knowledge Discovery from Sensor Data,” (http://books.google.com/books?id=dq7uAA3ssPcC) edited by a team led by Auroop Ganguly of ORNL’s Computational Sciences and Engineering Division. The book is specifically aimed at analyzing dynamic data streams from sensors that are geographically distributed. “We are especially interested in looking for changes – even ones that are very gradual — and anomalies,” Ganguly said. This work helps to validate and assign uncertainties to models developed to understand issues related to climate, transportation and biomass. Co-authors include Olufemi Omitaomu and Ranga Raju Vatsavai of ORNL. This research was originally funded by the Laboratory Directed Research and Development program. 

Cyber Security—Meeting of minds . . .

Dozens of the nation’s authorities on cyber security will be participating in the Fifth Cyber Security and Information Intelligence Research Workshop April 13-15 (http://www.ioc.ornl.gov/csiirw). The focus of this event, which is open to the public, is to discuss novel theoretical and empirical research to advance the field. “We aim to challenge, establish and debate a far-reaching agenda that broadly and comprehensively outlines a strategy for cyber security and information intelligence that is founded on sound principles and technologies,” said Frederick Sheldon, general chair and a member of Oak Ridge National Laboratory’s Computational Sciences and Engineering Division, a sponsor of the workshop. Other sponsors are the University of Tennessee and the Federal Business Council. The workshop, hosted by ORNL, is being held in cooperation with the Association for Computing Machinery. 

Material—Graphene cleanup . . .

Graphene, a single-layer sheet of graphite, has potential as a remarkable material, particularly for electronics and composite applications. However, working with the material leaves molecular-scale rough edges, which can spoil its properties. Researchers at MIT and the Laboratory for Nanoscience and Nanotechnology Research (LINAN) and Advanced Materials Department in San Luis Potosi, Mexico have been working with graphitic nanoribbons. Separate research performed at the Department of Energy’s Oak Ridge National Laboratory developed theory-based computer simulations with quantum mechanical calculations that explain how a process called Joule heating cleans up graphene as the rough carbon edges vaporize and then reconstruct at higher, voltage-induced temperatures. The collaborative project was recently described in Science magazine. 

Energy—Tighten up . . .

An effort to gather environmental data related to the energy efficiency of buildings through weatherization technologies will be conducted in a joint project that includes Oak Ridge National Laboratory’s Building Technologies, Research and Integration Center. ORNL engineer Andre Desjarlais says his group’s research will focus on the study of a building’s air tightness by monitoring unintended air movement – air leakage – between outdoors and indoors. In heating climates, up to 30 percent of the energy used in a building can be attributed to air leakage. The tests will be conducted at Syracuse University, which is also a partner. Other partners are the Air Barrier Association of America and it members, along with the New York State Energy Office. The DOE funding source is the Office of Building Technologies.