VO2-based electric-double-layer transistor in OFF and ON states |
Sixty
years after the transistor began a technological revolution that
transformed nearly every aspect of our daily lives, a new transistor
brings innovations that may help to do so again. Developed at RIKEN, the
device uses the electrostatic accumulation of electrical charge on the
surface of a strongly-correlated material to trigger bulk switching of
electronic state. Functional at room temperature and triggered by a
potential of only 1 V, the switching mechanism provides a novel building
block for ultra low power devices, non-volatile memory and optical
switches based on a new device concept.
After
shrinking for many decades, conventional electronics is approaching
quantum scaling limits, motivating the search for alternative
technologies to take its place. Among these, strongly-correlated
materials, whose electrons interact with each other to produce unusual
and often useful properties, have attracted growing attention. One of
these properties is triggered in phase transitions: applying a small
external voltage can induce a very large change in electric resistance, a
mechanism akin to a switch that has many potential applications.
Now,
researchers at the RIKEN Advanced Science Institute have created the
world’s first transistor that harnesses this unique property. Described
in a paper in Nature, the device uses an electric-double layer to tune
the charge density on the surface of vanadium dioxide (VO2), a
well-known classical strongly-correlated material. Thanks to the strong
correlation of electrons and electron-lattice coupling in VO2, this
surface charge in turn drives localized electrons within the bulk to
delocalize, greatly magnifying the change of electronic phase. A
potential of only 1 V, they show, is enough to switch the material from
an insulator to a metal and trigger an astounding thousand-fold drop in
resistance.
The
electronic phase, however, is not the only thing that changes in this
insulator-to-metal transition: using synchrotron radiation from RIKEN’s
SPring-8 facility in Harima, the research group analyzed the crystal
structure of the VO2, showing that it, too, undergoes a transformation,
from monoclinic to tetragonal structure. Electric-field induced bulk
transformation of this kind is impossible using conventional
semiconductor-based electronics and suggests a wide range of potential
applications.
First
released over sixty years ago to little fanfare, the transistor has had
a dramatic impact on our daily lives, powering the electronic devices
we use every day. The new switching mechanism takes this first discovery
to a new level, demonstrating that a very small electric potential is
enough to control macroscopic electronic states and offering a new route
to controlling the state of matter.
Collective bulk carrier delocalization driven by electrostatic surface charge accumulation
Source: RIKEN
