A fascinating Masters thesis written by Feng Xiong details the fabrication and testing of a phase-change memory (PCM) element using carbon nanotube FETs and “microbubbles” of GST to create extremely small, non-volatile memory elements. (GST is the chalcogenide glass material usually employed as the phase-change media in PCM and widely used as the active material in recordable CDs and DVDs.) Fusing a GST microbubble with a carbon nanotube FET produces an extremely small memory element with a measured programming current of 10 microamps—almost two orders of magnitude smaller than the figures published for the early commercial PCM devices just starting to appear after 40 years of PCM development. Feng Xiong is a Masters candidate in the Department of Electrical and Computer Engineering in the Graduate College of the University of Illinois at Urbana-Champaign and his work is pretty impressive.

Dropping the programming current of a PCM cell overcomes one of several major scalability problems associated with PCM. However, Xiong’s experiments are all about developing and characterizing one working PCM cell, not creating a process that can mass-produce billions of such cells on one chip. To do that, we still need to find ways to create carbon nanotubes at will, in exact sizes, placed regularly and precisely, billions of times per chip, chip after chip. We’re not there yet.