Abstract: Phosphorus doped (P-doped) nanogranular SiO₂ films have been deposited by plasma-enhanced chemical vapor deposition. A high proton conductivity of ~3.2 × 10^-4 S/cm and a large electric double layer (EDL) capacitance of ~3.2 μF/cm² have been obtained. Flexible coplanar-gate EDL thin film transistors (TFTs) gated by P-doped nanogranular SiO₂ films are self-assembled on plastic substrates at room temperature. Due to the big EDL capacitance, such TFTs show ultra-low voltage operation of 1 V, a large field-effect mobility of 18.9 cm²/Vs, a small subthreshold swing of 85 mV/decade and a high current on/off ratio of 10⁷. Furthermore, the EDL TFT could work in dual coplanar gate mode. AND logic operation is realized. Our results demonstrate that such TFTs gated by P-doped nanogranular SiO₂ films have potential applications in low-power flexible electronics.

Key words: Flexible devices, P-doped nanogranular SiO2, Electric-double-layer (EDL) effects, AND logic