Parylene-C and High-k Polymer Bilayer Gate Dielectric for Low-Operating Voltage Organic Field-Effect Transistors

Abstract

We propose a way to fabricate polymer insulators with a high gate capacitance for low-operating voltage organic field-effect transistors (OFETs). The insulator consists of spin-coated cyanoethylpullulan as a high-k polymer and chemical vapor deposited parylene-C as a covering layer. Parylene-C layer is insoluble in a common organic solvent, so the dielectric system can be fabricated on a layer of solution processable organic semiconductors such as poly(9,9-dioctylfluorene-co-bithiophene) (F8T2). The OFET shows a field-effect mobility of 3.4 × 10⁻³ cm²/Vs,a threshold voltage of − 1 V, and an on/off current ratio of 5.9 × 10². We successfully observed low-voltage operation in OFETs with this dielectric system.

Keywords:

• chemical vapor deposition
• gate dielectric
• high-k polymer
• organic field-effect transistors
• parylene-C