Graphene Chips

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Chips with graphene inside are theoretically quicker than plain silicon designs, but

they've been slow in practice; the manufacturing process often damages the graphene,

stripping away its speed advantage. That won't be a big problem with IBM's prototype

radio receiver, though. The company inserted graphene transistors into the new chip

only after it finished assembling the mostly silicon design, keeping the more exotic

material intact. The resulting integrated circuit is about 10,000 times more powerful

than previous parts, IBM claims.

Thanks to improvements in fiber optics, most of the information that you consume on

any given day is transported by light. Quite inefficiently, however, most computer chips

need electricity to operate, and scientists haven't quite figured out how to make the leap

to more futuristic materials. At least not until graphene came along.

A trio of studies was just published in Nature Photonics that detail a new technique for

using graphene as the light-friendly base for computer chips. A design by researchers at

MIT, Columbia and IBM's T.J. Watson Research Center calls for a layer of graphene

(pictured above as the hexagonal mesh) to go over a silicone waveguide (purple) and

between electrodes (gold). Any electrons knocked free from incoming light would be

converted into electrical energy. A chip built like this would not only be hyper responsive

and very fast; it would also be cheaper to manufacture than standard silicone chips.

These so-called graphene photodetectors would work for a number of different

purposes, both inside and outside computers. A team led by Thomas Müller from Vienna

University of Technology also integrated graphene photodetectors with silicone chips.

"There are many materials that can transform light into electrical signals, but graphene

allows for a particularly fast conversion," Müller explained in a press release. "These

technologies are not only important for transmitting data over large distances. Optical

data transmission also becomes more and more important for communication within

computers."

This is only the beginning for graphene-based computer chips. In fact, it's one of the

trendiertopics in fields like photonics. The sheer volume of research—three studies in

one journal!—is keeping many scientists hopeful that the material will soon make the

jump from the lab to the computer factory. In the meantime, chalk up another win for

graphene, one of the most amazingly versatile materials we've ever seen.

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IBM has built the world’s most advanced graphene-based chip, with performance that’s

10,000 times better than previous graphene ICs. The key to the breakthrough is a new

manufacturing technique that allows the graphene to be deposited on the chip without it

being damaged (something that has heretofore been very hard to achieve). Perhaps

more importantly, though, this new method is actually compatible with standard silicon

CMOS processes. In short, we are closer than ever before to realizing a commercial

graphene computer chip.

How IBM Research built a graphene integrated circuit

What IBM Research has built is a silicon chip, on a standard 200mm silicon wafer, using

a standard CMOS fabrication process. This chip, which is a radio frequency (RF)

receiver, is just a normal chip, with resistors, capacitors, and transistors — except for

one bit: the transistor channels are made of graphene. The chip’s function is very

rudimentary: It receives and restores wireless signals in the 4.3GHz range.

What’s the breakthrough, then? Basically, previous attempts at building GFETs

(graphene field-effect transistors) have used standard BEOL (back end of line)

processes, where the active components (the transistor and its graphene channel) are

built on the wafer first, and then the rest of the passive components (capacitors,

resistors) and interconnects are added. The problem is, due to graphene’s weak adhesion

and fragile single-atom-thick composition, this process damages the GFETs. To get

around this, IBM builds the passive components first, and then only deposits a layer of

graphene right at the end, to complete the fabrication of the transistors. It’s a relatively

simple change, but it works rather well. [Research paper: doi:10.1038/ncomms4086 -

"Graphene radio frequency receiver integrated circuit"]

A w a fer of g r a ph en e ch ips, bein g tested a t IBM Resea r ch

The graphene is grown in a furnace. A copper foil is placed in a furnace at 1,050C

(1,922F) with an atmosphere of methane, resulting in a single layer of graphene being

deposited on the foil. The copper is dissolved away in a bath, leaving a layer of graphene

floating there. The silicon wafer, with all the passive components already in place, is then

used to “scoop up” the graphene layer out of the bath. (Bear in mind that the graphene is

transparent, too.) This is currently the easiest way to grow large amounts of graphene,

but the IBM engineers told me that the quality of graphene grown in this way isn’t great,

and that having to destroy the copper substrate is expensive and inefficient.

Moving forward, it’s important to note that we’re still very much talking about an

analog chip. IBM Research still hasn’t found a way of giving graphene the all-important

bandgap that is required for the fabrication of digital logic, and thus graphene-based

computer processors. For next-gen processors, IBM seems to be focused on carbon

nanotubes, which can have a band gap, over graphene. Assuming we can one day create

large quantities of high-quality graphene, though, there are plenty of radio and optical

applications that could benefit — in theory, graphene is capable of operating at

frequencies as high as 500GHz, well beyond any other material currently used in RF

applications.

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Article Source:

● http://gizmodo.com/graphene-computer-chips-run-on-light-instead

-of-electri-1325215948