Computer processor made from carbon nanotubes

BBC : Subhasish Mitra and Max Shulaker of Stanford University and their colleagues have built a computer processor whose 178 FETs are each made from carbon nanotubes. Although the processor is only as capable as the ones inside a VAX-11 and other 1970s computers, the feat constitutes a major advance toward the goal of transcending the inherent limits of silicon-based computing. Transistors based on carbon nanotubes have been around for 15 years. Assembling them into a processor required devising a way to align the nanotubes, which usually emerge from the fabrication process in a noodle-like pile. The Stanford researchers grew theirs on a grooved wafer of quartz. Another challenge was to remove the fraction of nanotubes that are metallic rather than semiconducting. Pulsing an electric current through the device safely shut off the semiconducting nanotubes while heating the metallic ones to the point that they were oxidized and destroyed. On paper, carbon nanotube processors are faster and more energy efficient than their silicon counterparts. To realize those advantages, nanotube transistors must be made smaller. Although the individual nanotubes are just 10–100 nm long, the transistors in the Stanford processor are hundreds of times fatter than the most advanced silicon transistors.