Near IR Photoconductive Detector Based on f-MWCNTs/Polythiophen Nanocomposite

Abstract

Carbon nanotubes are an ideal material for infrared applications due to their
excellent electronic and photo electronic properties, suitable band gap, mechanical
and chemical stabilities. Functionalised multi-wall carbon nanotubes (f-MWCNTs)
were incorporated into polythiophen (PTh) matrix by electro polymerization
method. f-MWCNTs/ PTh nanocomposit films were prepared with 5wt% and
10wt% loading ratios of f-MWCNTs in the polymer matrix. The films are deposited
on porous silicon nanosurfaces to fabricate photoconductive detectors work in the
near IR region. The detectors were illuminated by semiconductor laser diode with
peak wavelength of 808 nm radiation power of 300 mW. FTIR spectra assignments
verify that the thiophene groups were successfully introduced into the carbon
nanotubes. SEM images reflect that the electro polymerization process gives well
incorporated for the MWCNTs by PTh polymer. Characteristics of photodetector
were improved after cooling the detector. Figure of merit showed a good IR
radiation sensitivity and photo response, while the specific detectivity was in order
of 109 cm.Hz1/2/W and at for both MWCNTs loading ratios at forward bias voltage
5 Volts. The rise time and fall time of the output signal are about 192 μs and 121μs
respectively which consider good values for these types of detectors.