Atomic-Layer-Deposited SnO2 as Gate Electrode for Indium-Free Transparent Electronics

Atomic‐layer‐deposited SnO 2 is used as a gate electrode to replace indium tin oxide (ITO) in thin‐film transistors and circuits for the first time. The SnO 2 films deposited at 200 °C show low electrical resistivity of ≈3.1 × 10 −3 Ω cm with ≈93% transparency in most of the visible range of the electromagnetic spectrum. Thin‐film transistors fabricated with SnO 2 gates show excellent transistor properties including saturation mobility of 15.3 cm 2 V −1 s −1 , a low subthreshold swing of ≈130 mV dec −1 , a high on/off ratio of ≈10 9 , and an excellent electrical stability under constant‐voltage stressing conditions to the gate terminal. Moreover, the SnO 2 ‐gated thin‐film transistors show excellent electrical characteristics when used in electronic circuits such as negative channel metal oxide semiconductor (NMOS) inverters and ring oscillators. The NMOS inverters exhibit a low propagation stage delay of ≈150 ns with high DC voltage gain of ≈382. A high oscillation frequency of ≈303 kHz is obtained from the output sinusoidal signal of the 11‐stage NMOS inverter‐based ring oscillators. These results show that SnO 2 can effectively replace ITO in transparent electronics and sensor applications.