
254 Nanosensors: Physical, Chemical, and Biological
On applying suitable gate bias, the device starts conducting with a maxi-
mum source–drain current I
sd (maximum)
given by
I
V
R
sd(maximum)
~
2
(4.62)
A closer introspection reveals that the current is maximum at a charge
Q
n e
=
2
(4.63)
and when
Q e= , the device returns to the state equivalent to zero gate bias.
Again, there is an energy gap between the states −(N + 1)e and −(N + 2)e. Thus
a cyclic process takes place with the current I
sd
oscillating between low and
high values. The period of oscillation in
Q
is |e|. This implies that the con-
ductivity of the island can be signicantly varied ...