Graphene Faces Real-World Limitations

By Tiffany Trader

May 5, 2014

Graphene is a one-atom-thick layer of carbon that has been hailed as a potential silicon replacement capable of extending the exponential computing advances that modern society has come to depend on. Despite the material’s profile of being strong, flexible, light-weight and a good conductor, there are still a number of challenges that must addressed before it is suitable for use in microprocessors and other electronics devices.

Researchers the world over are pushing hard to advance the status of this potential wonder material. This week two teams of scientists, one hailing from the University of Texas at Austin and the other a combined team from Rice University and the Georgia Institute of Technology, released different findings relating to graphene. The first sheds light on a particular thorny challenge regarding how graphene is used in real-world devices, and the second concerns the brittle nature of graphene sheets, which it has been found are only as strong as their weakest link. Computational modeling was integral to both projects.

The University of Texas at Austin team, led by Li Shi, a professor of mechanical engineering, along with graduate research assistant Mir Mohammad Sadeghi and post-doctoral fellow Insun Jo, structured an experiment in order to study thermal conductivity when the thickness of graphene on a substrate was increased. Thermal conductivity is a critical property as electronics components head to the nanoscale. It enables heat to distribute out such that hot spots are prevented. When graphene is in its ideal state, i.e. freely suspended in a vacuum, it is excellent thermal conductivity. Alas real-world conditions are not so ideal.

As Li Shi explains: “When you fabricate devices using graphene, you have to support the graphene on a substrate and doing so actually suppresses the high thermal conductivity of graphene.”

The team observed that thermal conductivity increased as the number of layers grew from a single one-atom layer up to 34 layers, but not to the point where it was as high as so-called bulk graphite, which is an excellent heat conductor.

The findings, which appear in the September 2013 issue of the Proceedings of the National Academy of Sciences, have prompted the team to explore new ways of supporting or connecting graphene with the macroscopic world. Among the techniques they are considering are three-dimensional interconnected foam structures of graphene and ultrathin graphite, as well as hexagonal boron nitride, which has a crystal structure very similar to graphene. Germanane is another material that shows promise for use in electronics or thermoelectric energy conversion devices.

The theoretical calculations that underpinned much of this work were performed on the 10-petaflop (peak) Stampede supercomputer. The NSF-funded system, one of the most powerful in the world, is housed at the Texas Advanced Computing Center (TACC) at The University of Texas at Austin.

“In order to really understand the physics, you need to include additional theoretical calculations. That’s why we use the supercomputers at TACC,” said Shi. “When you do an experiment, you see a trend, but without doing the calculations you don’t really know what it means. The combination of the two is very powerful. If you just do one without doing the other, you might not develop the understanding needed.”

In a separate study, researchers Jun Lou at Rice and Ting Zhu at Georgia Tech also look at the limitations of graphene in real-world settings. The bonds between carbon atoms are known to be the strongest in nature, and it follows that a perfect sheet of graphene would share this property, but in actual applications, graphene sheets do not live up to their theroetical promise. In a first of its kind experiment, the two researchers measured the fracture toughness of graphene that was marred with minor imperfections to simulate real-world conditions and found it to be “substantially lower” than the instrinsic strength of graphene.

“Everybody thinks the carbon-carbon bond is the strongest bond in nature, so the material must be very good,” Lou said. “But that’s not true anymore, once you have those defects. The larger the sheet, the higher the probability of defects. That’s well known in the ceramic community.”

The Rice team did the experiments and the Georgia Tech team ran computer simulations of the entire fracture process. The modeling was tightly coupled with the experiments, said Zhu.

Because most graphene has defects, its actual strength is likely to be significantly lower than the intrinsic strength of a perfect sheet of the atom-thick carbon material. The findings provide a deeper understanding of how defects will affect the handling, processing and manufacture of the materials, said Lou. It also demonstrates the importance of manufacturing graphene sheets that are made to exacting standards, as free from errors as is feasible.

Subscribe to HPCwire's Weekly Update!

Be the most informed person in the room! Stay ahead of the tech trends with industy updates delivered to you every week!

IBM Begins Power9 Rollout with Backing from DOE, Google

December 6, 2017

After over a year of buildup, IBM is unveiling its first Power9 system based on the same architecture as the Department of Energy CORAL supercomputers, Summit and Sierra. The new AC922 server pairs two Power9 CPUs with f Read more…

By Tiffany Trader

PEZY President Arrested, Charged with Fraud

December 6, 2017

The head of Japanese supercomputing firm PEZY Computing was arrested Tuesday on suspicion of defrauding a government institution of 431 million yen (~$3.8 million). According to reports in the Japanese press, PEZY founde Read more…

By Tiffany Trader

Azure Debuts AMD EPYC Instances for Storage Optimized Workloads

December 5, 2017

AMD’s return to the data center received a boost today when Microsoft Azure announced introduction of instances based on AMD’s EPYC microprocessors. The new instances – Lv2-Series of Virtual Machine – use the EPY Read more…

By John Russell

HPE Extreme Performance Solutions

Unleash the Next Generation of HPC with Memory-Driven Compute

Today’s enterprises are faced with an ever-growing volume of data that contains immense value and intelligence for those who can properly collect, process, and store it. Read more…

Bryant Departs Intel For Google Cloud

December 5, 2017

Google has upped its cloud game with its recruitment of Diane Bryant, the former Intel Corp.'s datacenter boss who becomes chief operating officer of Google Cloud. Bryant, an engineer who worked her way up through the Read more…

By George Leopold

IBM Begins Power9 Rollout with Backing from DOE, Google

December 6, 2017

After over a year of buildup, IBM is unveiling its first Power9 system based on the same architecture as the Department of Energy CORAL supercomputers, Summit a Read more…

By Tiffany Trader

Microsoft Spins Cycle Computing into Core Azure Product

December 5, 2017

Last August, cloud giant Microsoft acquired HPC cloud orchestration pioneer Cycle Computing. Since then the focus has been on integrating Cycle’s organization Read more…

By John Russell

GlobalFoundries, Ayar Labs Team Up to Commercialize Optical I/O

December 4, 2017

GlobalFoundries (GF) and Ayar Labs, a startup focused on using light, instead of electricity, to transfer data between chips, today announced they've entered in Read more…

By Tiffany Trader

HPE In-Memory Platform Comes to COSMOS

November 30, 2017

Hewlett Packard Enterprise is on a mission to accelerate space research. In August, it sent the first commercial-off-the-shelf HPC system into space for testing Read more…

By Tiffany Trader

SC17 Cluster Competition: Who Won and Why? Results Analyzed and Over-Analyzed

November 28, 2017

Everyone by now knows that Nanyang Technological University of Singapore (NTU) took home the highest LINPACK Award and the Overall Championship from the recently concluded SC17 Student Cluster Competition. We also already know how the teams did in the Highest LINPACK and Highest HPCG competitions, with Nanyang grabbing bragging rights for both benchmarks. Read more…

By Dan Olds

Perspective: What Really Happened at SC17?

November 22, 2017

SC is over. Now comes the myriad of follow-ups. Inboxes are filled with templated emails from vendors and other exhibitors hoping to win a place in the post-SC thinking of booth visitors. Attendees of tutorials, workshops and other technical sessions will be inundated with requests for feedback. Read more…

By Andrew Jones

SC Bids Farewell to Denver, Heads to Dallas for 30th Anniversary

November 17, 2017

After a jam-packed four-day expo and intensive six-day technical program, SC17 has wrapped up another successful event that brought together nearly 13,000 visit Read more…

By Tiffany Trader

SC17 Keynote – HPC Powers SKA Efforts to Peer Deep into the Cosmos

November 17, 2017

This week’s SC17 keynote – Life, the Universe and Computing: The Story of the SKA Telescope – was a powerful pitch for the potential of Big Science projects that also showcased the foundational role of high performance computing in modern science. It was also visually stunning. Read more…

By John Russell

US Coalesces Plans for First Exascale Supercomputer: Aurora in 2021

September 27, 2017

At the Advanced Scientific Computing Advisory Committee (ASCAC) meeting, in Arlington, Va., yesterday (Sept. 26), it was revealed that the "Aurora" supercompute Read more…

By Tiffany Trader

NERSC Scales Scientific Deep Learning to 15 Petaflops

August 28, 2017

A collaborative effort between Intel, NERSC and Stanford has delivered the first 15-petaflops deep learning software running on HPC platforms and is, according Read more…

By Rob Farber

Oracle Layoffs Reportedly Hit SPARC and Solaris Hard

September 7, 2017

Oracle’s latest layoffs have many wondering if this is the end of the line for the SPARC processor and Solaris OS development. As reported by multiple sources Read more…

By John Russell

AMD Showcases Growing Portfolio of EPYC and Radeon-based Systems at SC17

November 13, 2017

AMD’s charge back into HPC and the datacenter is on full display at SC17. Having launched the EPYC processor line in June along with its MI25 GPU the focus he Read more…

By John Russell

Nvidia Responds to Google TPU Benchmarking

April 10, 2017

Nvidia highlights strengths of its newest GPU silicon in response to Google's report on the performance and energy advantages of its custom tensor processor. Read more…

By Tiffany Trader

Japan Unveils Quantum Neural Network

November 22, 2017

The U.S. and China are leading the race toward productive quantum computing, but it's early enough that ultimate leadership is still something of an open questi Read more…

By Tiffany Trader

GlobalFoundries Puts Wind in AMD’s Sails with 12nm FinFET

September 24, 2017

From its annual tech conference last week (Sept. 20), where GlobalFoundries welcomed more than 600 semiconductor professionals (reaching the Santa Clara venue Read more…

By Tiffany Trader

Google Releases Deeplearn.js to Further Democratize Machine Learning

August 17, 2017

Spreading the use of machine learning tools is one of the goals of Google’s PAIR (People + AI Research) initiative, which was introduced in early July. Last w Read more…

By John Russell

Leading Solution Providers

SC17 Booth Video Tours Playlist

Amazon Debuts New AMD-based GPU Instances for Graphics Acceleration

September 12, 2017

Last week Amazon Web Services (AWS) streaming service, AppStream 2.0, introduced a new GPU instance called Graphics Design intended to accelerate graphics. The Read more…

By John Russell

Perspective: What Really Happened at SC17?

November 22, 2017

SC is over. Now comes the myriad of follow-ups. Inboxes are filled with templated emails from vendors and other exhibitors hoping to win a place in the post-SC thinking of booth visitors. Attendees of tutorials, workshops and other technical sessions will be inundated with requests for feedback. Read more…

By Andrew Jones

EU Funds 20 Million Euro ARM+FPGA Exascale Project

September 7, 2017

At the Barcelona Supercomputer Centre on Wednesday (Sept. 6), 16 partners gathered to launch the EuroEXA project, which invests €20 million over three-and-a-half years into exascale-focused research and development. Led by the Horizon 2020 program, EuroEXA picks up the banner of a triad of partner projects — ExaNeSt, EcoScale and ExaNoDe — building on their work... Read more…

By Tiffany Trader

Delays, Smoke, Records & Markets – A Candid Conversation with Cray CEO Peter Ungaro

October 5, 2017

Earlier this month, Tom Tabor, publisher of HPCwire and I had a very personal conversation with Cray CEO Peter Ungaro. Cray has been on something of a Cinderell Read more…

By Tiffany Trader & Tom Tabor

Tensors Come of Age: Why the AI Revolution Will Help HPC

November 13, 2017

Thirty years ago, parallel computing was coming of age. A bitter battle began between stalwart vector computing supporters and advocates of various approaches to parallel computing. IBM skeptic Alan Karp, reacting to announcements of nCUBE’s 1024-microprocessor system and Thinking Machines’ 65,536-element array, made a public $100 wager that no one could get a parallel speedup of over 200 on real HPC workloads. Read more…

By John Gustafson & Lenore Mullin

Flipping the Flops and Reading the Top500 Tea Leaves

November 13, 2017

The 50th edition of the Top500 list, the biannual publication of the world’s fastest supercomputers based on public Linpack benchmarking results, was released Read more…

By Tiffany Trader

Intel Launches Software Tools to Ease FPGA Programming

September 5, 2017

Field Programmable Gate Arrays (FPGAs) have a reputation for being difficult to program, requiring expertise in specialty languages, like Verilog or VHDL. Easin Read more…

By Tiffany Trader

HPC Chips – A Veritable Smorgasbord?

October 10, 2017

For the first time since AMD's ill-fated launch of Bulldozer the answer to the question, 'Which CPU will be in my next HPC system?' doesn't have to be 'Whichever variety of Intel Xeon E5 they are selling when we procure'. Read more…

By Dairsie Latimer

Share This