Page 57 - Organic Electronics in Sensors and Biotechnology

34 Chapter One

3
60 nm Grain ~ 80 nm
150 nm
Normalized drain current 2 1
450 nm
1 μm

0
0 10 20 30 40 50 60
Time (s)
(a)

60 nm
150 nm
3 450 nm
Normalized drain current 2
1 μm

1

Grain ~ 250 nm
0
0 10 20 30 40 50 60
Time (s)
(b)

FIGURE 1.18 The sensing effects of nanoscale pentacene transistors upon
exposure to 1-pentanol. (a) Sensing data of I (normalized to that
ds
measured just before the analyte took effect) for 80 nm pentacene grain
size and different nanoscale channel lengths (same W/L = 10), measured
at V = V = V =−2.5 V (two side guards were kept at the same potential
g ds side
as the drain), v (analyte fl ux) = 45 mL/min, d (distance from syringe nozzle
to device) = 2 mm. (b) Sensing data of normalized I for 250 nm pentacene
ds
grain size, measured at the same conditions as (a). (Reprinted with
permission from Ref. 115. Copyright 2004, American Institute of Physics.)
the response of pentacene transistors to the 1-pentanol vapor changes
from decreasing I to increasing I , when the channel length shrinks
ds ds
from micron to 100 nm scale, with a crossover happening in a transi-
tion interval of channel length which is related to the grain sizes of
pentacene.