The figure shows a schematic of a nanofluidic circuit that operates by passing ionic fluid (green) through conduits fabricated on top of a planar oxide surface (orange). A voltage is applied to the liquid (blue gate) which results in the electric field induced motion of oxygen ions (yellow balls) from the oxide surface into the liquid. This results in the metallization of the oxide (redder region) beneath the liquid that is subject to the gate voltage. Where no voltage is applied (pale blue gate) there is no ionic motion and the oxide surface remains insulating. Thus circuits can be dynamically formed in the surface of the oxide. Reverse gating results in the reverse motion of oxygen and the oxide returns to its insulating state.
Optical image of a typical ionic liquid (IL) gated device with a droplet of IL on top of the gate electrode and the oxide channel. The gold squares are pads used to make contact to the device via wire-bonding. On right is the magnified image of the device showing the channel (brownish yellow) and the gold electrical contacts (bright yellow). The contacts on the right and left of the channel are the source and drain contacts. The four other contact are used for 4-wire resistance & Hall measurements.
IBM Research News: Breakthrough discovery flips material from insulating to conductive state using tiny ionic currents
For decades the transistor as we know has gone through very little change. As semiconductor chips continue to scale, the materials and techniques to build chips are rapidly approaching physical and performance limitations. New solutions need to be developed that are more efficient and higher performing.
Metal oxides have been around for quite some time and being able transitioning this material from an insulator to a conducting metal has already been accomplished. However, being able to transition the material to a stable enough state so it can be used as a switch has been the biggest challenge.
By applying a charged ionic liquid electrolyte to the substance, IBM Researchers have cracked the code to maintaining a stable insulating and conducting state of the oxide material. This new discovery opens up a path for making oxide based switches and logic gates a standard in the semiconductor chip manufacturing process of the future.
Schematic image of a typical ionic liquid (IL) gated device showing the channel, the source and drain contacts, and the gate electrode with a droplet of the IL on top.
San Jose, Calif., – 22 March, 2013: IBM (NYSE: IBM) today announced a materials science breakthrough at the atomic level that could pave the way for a new class of non-volatile memory and logic chips that would use less power than today’s silicon based devices. Rather than using conventional electrical means that operate today’s semiconducting devices, IBM’s scientists discovered a new way to operate chips using tiny ionic currents, which are streams of charged atoms that could mimic the event-driven way in which the human brain operates.
Today’s computers typically use semiconductors made with CMOS process technologies and it was long thought that these chips would double in performance and decrease in size and cost every two years. But the materials and techniques to develop and build CMOS chips are rapidly approaching physical and performance limitations and new solutions may soon be needed to develop high performance and low-power devices.
IBM research scientists showed that it is possible to reversibly transform metal oxides between insulating and conductive states by the insertion and removal of oxygen ions driven by electric fields at oxide-liquid interfaces. Once the oxide materials, which are innately insulating, are transformed into a conducting state, the IBM experiments showed that the materials maintain a stable metallic state even when power to the device is removed. This non-volatile property means that chips using devices that operate using this novel phenomenon could be used to store and transport data in a more efficient, event-driven manner instead of requiring the state of the devices to be maintained by constant electrical currents.
“Our ability to understand and control matter at atomic scale dimensions allows us to engineer new materials and devices that operate on entirely different principles than the silicon based information technologies of today,” said Dr. Stuart Parkin, an IBM Fellow at IBM Research. “Going beyond today’s charge-based devices to those that use miniscule ionic currents to reversibly control the state of matter has the potential for new types of computing devices. Using these devices and concepts in novel three-dimensional architectures could prevent the information technology industry from hitting a technology brick wall.”
To achieve this breakthrough, IBM researchers applied a positively charged ionic liquid electrolyte to an insulating oxide material - vanadium dioxide - and successfully converted the material to a metallic state. The material held its metallic state until a negatively charged ionic liquid electrolyte was applied, to convert it back to its original, insulating state.
Such metal to insulator transition materials have been extensively researched for a number of years. However, contrary to earlier conclusions, IBM discovered that it is the removal and injection of oxygen into the metal oxides that is responsible for the changes in state of the oxide material when subjected to intense electric fields.
The transition from a conducting state to an insulating state has also previously been obtained by changing the temperature or applying an external stress, both of which do not lend themselves to device applications.
This research was published yesterday in the peer-reviewed journal Science.