nanotehnoloogia, nanoteknologia, nanotechnologija, nanotehnologijas, nanoteknologija,
nanotechnologii, nanotecnologia, nanotehnologijo, nanoteknik
Scientists have demonstrated the first reproducible,
controllable silicon transistors that are turned
on and off by the motion of individual electrons.
The experimental devices, designed and fabricated
at NTT Corp. of Japan and tested at NIST, may have
applications in low-power nanoelectronics, particularly
as next-generation integrated circuits for logic
operations (as opposed to simpler memory tasks).
The transistors, described in the Jan. 30, 2006,
issue of Applied Physics Letters,* are based on the
principle that as device sizes shrink to the nanometer
range, the amount of energy required to move a single
electron increases significantly. This makes it possible
to control individual electron motion and current
flow by manipulating the voltage applied to barriers,
or "gates," in the electrical circuit. At negative
voltage, the transistor is off; at higher voltage,
the transistor is turned on and individual electrons
file through the circuit, as opposed to thousands
at a time in a conventional device.
This type of innovative transistor, called a "single-electron
tunneling" (SET) device, is typically made with a
metal "wire" interrupted by insulating barriers that
offer a rigid, narrow range of control over electron
flow. Silicon devices, by contrast, have barriers
that are electrically "tunable" over a wider operating
range, offering finer, more flexible control of the
transistor's on/off switch. Particular voltage levels
are applied across the barriers, to manipulate charge,
as a means of encouraging or impeding electron flow.
Silicon-based devices also allow fabrication using
standard semiconductor technology. Until now, however,
no silicon SET transistor designs have been reported
that are reproducible and controllable.
The NIST/NTT team made five uniform, working silicon
transistors with tunable barriers. Each device consists
of a silicon channel 360 nanometers (nm) long and
30 nm wide, with three gates crossing the channel.
The gates have two levels; the upper level turns
the current on and off, while the lower level controls
electron flow in small local areas. The team was
able to tune gate conductance properties over a wide
range, by more than three orders of magnitude.
This work was partly supported by the Japan Society
for the Promotion of Science.
*A. Fujiwara, H. Inokawa, K. Yamazaki, H. Namatsu,
Y. Takahashi, N.M. Zimmerman, and S.B. Martin. 2006.
Single electron tunneling transistor with tunable
barriers using silicon nanowire MOSFET. Applied Physics
Letters. Jan. 30.
Contact: Laura Ost
National Institute of Standards and Technology