IBM is reporting success with a new fabrication process that puts carbon nanotubes on the surface of a silicon wafer to build chips with more than 10,000 working transistors. Carbon what? Carbon nanotubes. They're molecules that have long been discussed as a viable successor to silicon. They are extremely thin hollow cylinders made of carbon atoms and have a diameter about 10,000 times smaller than a human hair. Depending on their structure, IBM says, they can be metals or semiconductors. They’re extremely strong and have good thermal conductivity, which makes them a perfect material for making unimaginably small logic switches that can be jammed into microprocessors in astonishing numbers. A bit more science: At 9 nanometers, the new transistors are smaller than the physical limit of silicon, which is 11 nanometers. A carbon nanotube transistor also switches at a lower voltage than silicon, making it far more efficient. Although at the moment these transistors are prohibitively expensive to produce, their eventual arrival in the marketplace, perhaps near the end of this decade, ensures that Moore’s Law, which dictates that the number of transistors on a single chip doubles every 12 to 18 months (and has held true for 50 years) is safe for the time being, even as silicon reaches its limit.