Wednesday, February 4, 2009

Graphene and Graphane

News out of the labs on graphene is coming fast and furious. We are learning to manipulate it and to fabricate characteristics. By simply adding in hydrogen and we have no clue as to how, a single layer is turned into an insulator. Already, we can think semiconductors.

The newly announced single layer material is called graphane which is going to cause all end of confusion.

We very suddenly can imagine a layer of graphine that is altered chemically into various devices, perhaps by laser printing. Again the speed of research here is breathtaking.

I have posted two recent articles that demonstrate what is taking place. I wonder if graphene demonstrates any super conductor characteristics.

New products are been created by simple bombardment of the original graphene with a range of other elements.

The second article is controlling outcomes by altering the substrate on which the graphene is deposited.

Scientists Invent One-Atom-Thick Crystal Graphane was obtained from graphene
By Tudor Vieru

31 January, 2009

Scientists at the University of Manchester, who first discovered graphene, were also behind the creation of the new material, which differs from its predecessor through the fact that it also incorporates hydrogen atoms, which it attracts towards its ultra-thin structure. Basically, one could say that graphane, the new material, and graphene only have two sides, because their depth is only one atom, which by all accounts means it's invisible. Professor Andre Geim and Dr. Kostya Novoselov, the experts behind the 2004 research that yielded graphene, published the discoveries related to the new material on Friday, January 30th, in the prestigious journal Science.

The experts announced that the new material was obtained by making graphene react with various other substances, and added that the ones containing hydrogen were just one of many possibilities. Already, the material discovered in 2004 opened up new avenues for physics and material sciences, through the fact that it behaved like a never-before-encountered semiconductor. Its potential for transporting electrical current is impressive, which makes graphene one of the revolutionary materials to be employed in the construction of many types of innovative electronics.

On the other hand, the new material, graphane, exhibits insulating properties, which means that it could be used as an isolation around the circuits made from its predecessor. “Our work proves that this is a viable route and hopefully will open the floodgates for other graphene-based chemical derivatives. This should widen the possible applications dramatically,” Dr. Novoselov said about the new material.

“The modern semiconductor industry makes use of the whole period table: from insulators to semiconductors to metals. But what if a single material is modified so that it covers the entire spectrum needed for electronic applications? Imagine a graphene wafer with all interconnects made from highly conductive, pristine graphene whereas other parts are modified chemically to become semiconductors and work as transistors,” adds professor Geim, who is also a scientist at the University’s School of Physics and Astronomy.

The team plans to develop other crystalline compounds of graphene by using roughly the same technique used to create graphane, namely bombarding the 2004 compound with atoms of various substances. This might make them become insulators or semiconductors, or any other type of material the researchers could think of.

Researchers Discover Method for Controlling Graphene

New method allows researchers to make graphene with semiconductor or metallic properties at willToday, the interconnects in a CPU or any other electronic device using a semiconductor are made from copper. Scientists are looking at ways to use new material for these interconnects using substances that are faster and produce less heat.

One of the new materials with the most potential is called graphene. Researchers at the
Rensselaer Polytechnic Institute claim that they have discovered a new method for controlling graphene's nature. Graphene is a one-atom thin sheet of carbon that was discovered in 2004.

Graphene is being used by researchers at Rice University to make a
new type of memory that could one day replace flash storage. Before graphene memory and other nanoelectronics using graphene can become a reality, researchers have to find more effective methods of producing graphene with the properties they need.

Rensselaer researcher Saroj Nayak and a postdoctoral research associate have demonstrated a new method that can be used to control the nature of graphene. According to the pair, the nature of graphene can be controlled depending on the substrate on which it is grown, thus shaping its conductive properties.
Results based on large-scale quantum mechanical simulations show that graphene deposited on a surface treated with oxygen results in semiconductor properties while graphene deposited on a surface treated with hydrogen exhibits metallic properties.

This is a key discovery according to the researchers because when a conventional batch of graphene is produced some of it has semiconductor properties and some has metallic properties. The researchers say that using conventional methods it would be impossible to extract one form of graphene. Devices based on graphene would need to have only one graphene form in order to function.

Nayak said in a statement, "Depending on the chemistry of the surface, we can control the nature of the graphene to be metallic or semiconductor. Essentially, we are ‘tuning’ the electrical properties of material to suit our needs."

The reason researchers are pushing so hard to discover better methods for the production of graphene is that the substance could one day replace silicon and copper as the building blocks of electronics. Graphene has excellent conductive properties and at room temperature, electrons can pass through it at close to the speed of light with very little resistance.

Interconnects made from graphene would therefore create much less heat and would be able to run cooler. Cooler interconnects are important because heat can have a negative effect on a CPUs speed and performance. Just consider the huge increases overclockers are able to get out of a CPU when it is cooled more efficiently as an example.

The results of the study by the Rensselaer researchers was published in a paper this week titled "Electronic structure and band-gap modulation of graphene via substrate surface chemistry" published in Applied Physics Letters' January issue.

It is interesting to note that the researchers who were trying to make memory using graphene were using ten atom thick sheets of graphene, whereas the researchers at Rensselaer are using single atom thick graphene sheets.


Zhiping said...

how could this be related to global warming?

arclein said...

Always a good question although I certainly do not maintain a narrow focus.

However, global warming and the human response to global warming is all about terraforming the Earth.

It is about superior technology for energy conversion and storage.

Most of our applications breakthrough are coming by way of so called nano technology.

Graphine and metglas are right up front in that world.

In fact our developing mastery, which is happening now, is the most under reported revolution in history because we have learned to take it for granted.

We are gaining the tools now to completely alter the global environment everywhere. It is all part of a web of tech change upon us now.

Zhiping said...

Hi arclein, thanks a lot for the explanation. I am actually a researcher (theory and simulation) working on nano-materials and their application in energy-related issues. Sometimes I am getting lost in the words "global warming", "renewable energy" which are everywhere now.
I had some experience with hydrogen storage using nano-structures. Carbon nanotubes and graphene are good candidate but they can't hit the DOE 2010 goal yet, even from a theoretical point of view. Reasons are the reversibility of the storage can't be guaranteed and the porous or cage-like structures made of graphene and carbon nanotube is hard. Although his is a hot topic now, personally I don't expect too much future on this way. Anyway the report is interesting itself.