Fabrication of Poly(triaryl amine) Field-effect Transistors

PTAA Description

Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA; 702471) is an amorphous p-type polymer semiconductor.^{1, 2} It may be used to fabricate field-effect transistors (FETs). PTAA is also useful as a hole transport material in organic light emitting diodes (OLEDs).

Procedure for Fabrication of PTAA Field-effect Transistors

Bottom-gate bottom-contact field-effect transistors (FETs) were fabricated in a nitrogen atmosphere on highly doped Si-wafers with a thermally grown 250 nm SiO₂ layer. The two layers served as the gate electrode and gate insulator. Au source and drain electrodes (30 nm thick) were defined by standard photolithography:

channel length (L) = 10 mm
channel width (W) = 10 mm

Before deposition of the PTAA polymer layer, the Si-wafers were treated with octyltrichlorosilane (OTS-18; 104817 ) by immersing them in 10 mM solutions in toluene for 15 minutes at 60 °C.

A homogeneous solution of PTAA was prepared in toluene at room temperature containing 1.0 wt% of the polymer. This solution was deposited via spin-coating at 500 rpm for 30 seconds followed by 2,000 rpm for 50 seconds.

Results

Electrical characterization of the PTAA FETs was conducted in a nitrogen atmosphere with a HP4155B semiconductor parameter analyzer. Field-effect mobilities were calculated from transfer characteristics (saturation regime) employing the relation:³

Isd is the source-drain current (saturation regime)
Vg and Vsd gate and soxce-drain voltage, respectively
Ci the insulator capacitance
W and L the channel width and length
V₀ the turn-on voltage

Transfer and output curves for PTAA transistors are shown in Figures 1 and 2.

Data courtesy of Dr. Iain McCulloch, Imperial College London and Flexink, Inc.