Transistor

Scientists make world’s thinnest transistor – at three atoms thick

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    • In what could be the development that keeps Moore’s law plugging along, scientists in the US have produced a transistor that’s just a few atoms thick, opening up the possibility of some ridiculously tiny electronics.

      First proposed in 1965, Moore’s law predicts that the overall processing power of computers will double every two years, and while it’s still pretty much accepted as a rule, people have started to doubt its longevity. Surely there’s a limit to how many transistors we can pack into an integrated circuit? Well, if there is, it looks like we haven’t hit it yet, because a team from Cornell University in the US have achieved a pretty significant record with their new tiny transistor.

      The transistor is made using two-dimensional semiconductors known as transition-metal dichalcogenides (TMDs). When reduced to a single layer, these TMDs are just three atoms thick, made from members of a family of elements called transition metals. One of these, molybdenum disulfide, is a type of silvery, black metal that’s been touted for its superior electrical qualities over the past few years.

      The team crystallised it down, and figured out how to peel ultra-thin sheets just a few atoms thick from the surface of the crystals. Amazingly, even at this thickness, the molybdenum disulfide film retained its electrical properties, which makes it a promising candidate for use in future electronics. “The electrical performance of our materials was comparable to that of reported results from single crystals of molybdenum disulfide, but instead of a tiny crystal, here we have a 4-inch (10-cm) wafer,” one of the team, Jiwoong Park, said in a press release.

      To create this atoms-thick molybdenum disulfide film, the team used a technique called metal organic chemical vapour deposition (MOCVD), which involves starting with a powdered form of the material, converting that into a gas, and sprinkling single atoms onto a substrate, one layer at a time.

      “The process starts with two commercially available precursor compounds – diethylsulfide and a metal hexacarbonyl compound – mixed on a silicon wafer and baked at 550 degrees Celsius for 26 hours in the presence of hydrogen gas,”explains Russell Brandom at The Verge. “The result was an array of 200 ultra-thin transistors with good electron mobility and only a few defects. Just two of them failed to conduct, leaving researchers with a 99 percent success rate.”

      Publishing in Nature, the team says the next step is to figure out how to produce the film in a more consistent way, so the conductivity can be more accurately measured. But what they’ve achieved so far is a real step in the right direction.

      “Lots of people are trying to grow single layers on this large scale, myself among them,” materials scientist Georg Duesberg from Trinity College Dublin in Ireland, who was not involved in the research, told Elizabeth Gibney at Nature. “But it looks like these guys have really done it.”

 

Biological computer that ‘lives’ inside the body comes one step closer as scientists make transistor out of DNA and RNA.

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Molecular computer graphic of DNA double helixMolecular computer graphic of DNA double helixMolecular computer graphic of DNA double helixmolecular_computer3Finding could lead to new biodegradable devices based on living cells that are capable of detecting changes in the environment

Scientists believe they are close to building the first truly biological computer made from the organic molecules of life and capable of working within the living cells of organisms ranging from microbes to man.

The researchers said that they have made a transistor – the critical switch at the heart of all computers – from DNA and RNA, the two biological molecules that store the information necessary for living things to replicate and grow.

Silicon transistors control the direction of flow of electrical impulses within computer chips, but the biological transistor controls the movement of an enzyme called RNA polymerase along a strand of the DNA molecule, the scientists said.

Ultimately, the aim is to use the biological transistors – called transcriptors – to make simple but extremely small biological computers that could be programmed to monitor and perhaps affect the functioning of the living cells in which they operate, researchers said.

It could lead to new biodegradable devices based on living cells that are capable of detecting changes in the environment, or intelligent microscopic vehicles for delivering drugs within the body, or a biological monitor for counting number of times a human cell divides so that the device could destroy the cell if it became cancerous, the scientists said.

“Biological computers can be used to study and reprogram living systems, monitor environments and improve cellular therapeutics,” said Drew Endy, assistant professor of bioengineering at Stanford University in California, who led the study published in the journal Science.

Last year, Professor Endy announced new ways of using biological molecules to store information and to transmit data from one cell to another. The latest study adds the third critical component of computing – a biological transistor that acts as a “logic gate” to determine whether a biochemical question is true or false.

Logic gates are critical for a computer to function properly. In a biological setting the use of logical data processing is almost as limitless as its use in conventional electronic computing, said Jerome Bonnet, a bioengineer within the Endy laboratory, and the lead author of the study.

“You could test whether a given cell had been exposed to any number of external stimuli – the presence of glucose and caffeine for instance. [Logic] gates would allow you to make the determination and store that information so you could easily identify those which had been exposed and which had not,” Dr Bonnet said.

Biological computers have been the dream of electronic engineers for decades because they open the possibility of a new generation of ultra-small, ultra-fast devices that could be incorporated into the machinery of living organisms.

“For example, suppose we could partner with microbes and plants to record events, natural or otherwise, and convert this information into easily observed signals. That would greatly expand our ability to monitor the environment,” Professor Endy said.

“So the future of computing need not only be a question of putting people and things together with ubiquitous silicon computers. The future will be much richer if we can imagine new modes of computing in new places and with new materials – and then find ways to bring those new modes to life,” he said.

Source: http://www.independent.co.uk