Nanowires, nanoribbons and 'graphane' among materials that'll revolutionize computers

Architects of the next generation of computers are developing a variety of nanostructures to meet the demand for increasingly smaller features for semiconductors, microprocessors, and other components.

These tiny building blocks are quite extraordinary-some even self-assemble. And they'll help overcome many of the limitations of today's microelectronics such as scalability, speed, and durability, all while keeping on track with Moore's Law.  For instance, nanostructures are paving the way for advanced integrated circuits that will make today's silicon-based chips seem gigantic, and simply give entire industries a makeover. (To think some day people will have a similar response when viewing a blade server as we do when we see the ENIAC.)

You probably have heard of carbon nanotubes and read quite a bit about them, so let's take the bulk of this post to look at some of the latest research around other types of nanostructures:

Nanowires

These nanostructures are like regular electrical wires, just magnitudes smaller. They can be made of a semiconductor material and be used to link tiny nanoscale components together. Their size, which range from 100 nanometers to just 3 nanometers (100 nm is a ten-thousandth of a millimeter or a 1/500 of a human hair) means that they have quantum mechanical effects that open up new possibilities such as Quantum Tunneling, an effect that explains phenomena found in the physics of electronics.

Xiuling Li and graduate research assistant Seth Fortuna in the Micro and Nanotechnology Laboratory at University of Illinois.

Recently, researchers at the University of Illinois developed a technique that uses self-assembled, self-aligned, and defect-free nanowire channels made of gallium arsenide (a semiconductor) to make transistors smaller and faster. The nanowire was grown by metal organic chemical vapor deposition using gold as a catalyst, while the rest of the transistor was made with conventional microfabrication techniques.

But nanowires are no one-trick pony, and experimentation is taking the material in new directions.

Researchers at Penn State's Nanofabrication Laboratory have developed a new technique for assembling nanowires which could eventually allow for the development of handheld ultra-portable devices that can identify and instantly report on a broad array of substances.  They took DNA-coated wires and placed them exactly in a specified position, with an error rate of less than 1%. This precision is required to control the spatial placement on the chip with accuracy of less than a micron in order to simultaneously detect different pathogens or diseases based on their nucleic acid signatures, according to a story from The Future of Things.

The new technology could eventually lead to the design of a circuit chip with biologically tagged nanowires which could perform the same function.

In the non-conducting department, physicists at LMU Munich have found a new application for similar structures called nanostrings that can detect single molecules with high precision. The team constructed a system of nanostrings where each string can be electrically excited separately.  Thousands of the strings can be produced on a small chip.

According to Nanotechnology Now,  one of the devices that could be created with this system is a highly sensitive "artificial nose" that detects various molecules – pollutants for example – individually. The article says that these new nano-electromechanical systems could also be used in a multitude of other applications – acting as tiny pulse generators in mobile phone clocks, for example.

Nanoribbons

Graphene nanoribbons are thin strips of graphene or unrolled single-walled carbon nanotubes that have semiconductive properties.

This month, a team led by Hongjie Dai at Stanford University reported that they've developed a new method that will allow relatively precise production of mass quantities of the tiny ribbons by slicing or "unzipping" open carbon nanotubes.  Large quantities of uniform nanoribbons are needed to conduct extensive studies for electronics applications.

In order to slice and flatten out the delicate structures they had to approach the task with a tender touch, according to a press release:

Carbon nanotubes are placed on a substrate, then coated with a polymer film. The film covers the entire surface of each nanotube, save for a thin strip where the nanotube is in contact with the substrate. The film is easily peeled off from the substrate, taking along all the nanotubes and exposing the thin strip of polymer-free surface on each of them. A chemical etching process using plasma can then slice open each nanotube along that narrow strip. It's not unlike generating flat linguini noodles by slicing open bucatini, a long tubular pasta.

The method is surprisingly simple compared to other methods of nanoribbon production and the process can be extremely efficient. "We can open up every carbon nanotube at the same time and convert many nanotubes into ribbons at the same time," Dai said.

However, their role in microchips is still uncertain. "How much better computer chips using graphene nanoribbons would be than silicon chips is an open question," Dai said. "But there is definite potential for them to give a very good performance."

Graphane (with an "a")

Credit: University of Manchester

Graphene has highly conductive properties which makes it a hot item among computer scientists. Taking the material one step further,  researchers at the University of Manchester have produced a ground-breaking new material, graphane, which has been derived from graphene.

An article states that Professor Andre Geim and Dr Kostya Novoselov used hydrogen to react with graphene to materialize new compounds with distinctive characteristics.

The discovery that graphene can be modified into new materials, fine tuning its electronic properties, has opened up the increasingly rich possibilities in the development of future electronic devices from this truly versatile material.

Professor Geim shared some ideas on what that could mean to the tech industry:

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.

The Future of Things also covered this story, and has addtional content around graphene.