June 11, 2007 – Researchers from the National Institute of Standards and Technology (NIST), George Mason U., and Korea’s Kwangwoon U. have fabricated a hybrid memory device incorporating both silicon nanowires and nonvolatile semiconductor-oxide-nitride-oxide-semiconductor (SONOS) technology, which they suggest is more reliable than other nanowire-based memory devices.
Describing their work, the scientists say the nanowires were grown onto a layered oxide-nitride-oxide substrate. A positive applied voltage causes electrons to tunnel down from the wires into the substrate, which gives it charge; a negative voltage causes the electrons to tunnel back up into the wires. When fully charged each nanowire device stores a single bit of information (0 of 1 depending on the electrons’ position), and information is read with no voltage present.
The researchers say the combination of “excellent electronic properties” of nanowires with SONOS gives the device characteristics that are promising for nonvolatile memory applications — it has simple read, write, and erase capabilities, has a large memory window (indicating good memory retention and high resistance to outside voltages, ), and has a large on/off current ratio to distinguish between the 0 and 1 states. It also promises better stability at higher temperatures and easier integration into existing chip fabrication technology than other proposals for nanowire-based memory devices, NIST says.