Nanogranular Al2O3 proton conducting films for low-voltage oxide-based homojunction thin-film transistors

Nanogranular Al2O3 films were deposited by the plasma-enhanced chemical vapor deposition (PECVD) method using gas sources of trimethylaluminum and oxygen at 100 degrees C. Structural characterizations indicate that the as-deposited nanogranular Al2O3 film has an amorphous structure with excess oxygen due to ambient humidity and residual hydroxyl. As-deposited Al2O3 films show a mean pore size of 7.4 nm, and a high proton conductivity of 1.2 x 10(-4) S cm(-1) at room temperature with a 30% relative humidity. Low-voltage (1.5 V) indium-tin-oxide (ITO) thin-film transistors gated by such nanogranular Al2O3-based proton conductors exhibit a large current on/off ratio of 2.1 x 10(7) and a high field-effect mobility of 29 cm(2) V-1 s(-1). Our results demonstrate that nanogranular Al2O3-based films are promising gate dielectric candidates for portable biosensors.