The process ow for dual layer nanocomposite FETs with
randomoriented nanowires is shown in Fig. 1. Note that for elec
trical characterization no eld effect was observed from these low
density nanowire networks, indicating no direct connection
formed by nanowires between sourcedrain electrodes. Fig. 2
shows the output and transfer characteristics of a dual layer Si
P3HT and a pristine P3HT FETs, respectively, where the former
contains a nanowire density of N ¼ 0.4 (average number of NWs per
10 10 mm2). The IDSVDS curves clearly resemble those as typical p
channel accumulation mode eld effect behavior, where negative
IDS increases linearly with negative VDS at low VDS and saturates at
higher (more negative) applied VDS. The output currents of the dual
layer SiP3HT transistor are much higher than those of pristine
P3HT device; at VDS ¼ 40 V, VGS ¼ 40 V, for instance, the IDS of the
SiP3HT FET is up to 5 mA whereas that of the pristine one is 0.7 mA.
This enhancement in current output is a clear indication of that the
presence of Si nanowire network has a positive in uence on the
electrical conduction of the channel layer.
When the transfer characteristics were measured in the satu
ration regime (VDS ¼ 40 V), the effective mobility was calculated
by plotting the square root of the absolute drain current versus the
gate voltage and tting the slope data to Eqn. (1). The saturation
eld effect mobility of pristine P3HT device is 7.3 103 cm2V1s1.
For this dual layer SiP3HT FET, its carrier mobility is increased to
4.7 102 cm2V1 s1, representing an enhancement of ~six times
over the pristine P3HT device. The ON/OFF current ratio of both
devices remains in the same order of 104. In consequence, these