Low-voltage organic thin-film transistors with hydrophobic hafnium oxynitride film as gate insulator

An excellent gate dielectric of amorphous HfON (a-HfON) can be fabricated by flashing a Hf metal layer prior to a-HfON deposition. Nitrogen incorporation in the HfON film can reduce leakage current density from 8 × 10−7 to 10−7 A/cm2. And surface roughness of a-HfON is reduced by the flash Hf metal layer from 1.9 to 1.2 nm. With the flash Hf metal layer, field effect mobility (0.17 cm2/V s), threshold voltage (−0.3 V), subthreshold swing (−0.209 V/decade), and on/off current ratio (3.2 × 103) can be achieved for organic thin-film transistors with a-HfON gate dielectric.