Effects of annealing on electrical performance of multilayer MoS₂ transistors with atomic layer deposited HfO₂ gate dielectric

Atomic layer deposited HfO2 annealed in different ambients (N2, O2, and NH3) is used to replace SiO2 as a gate dielectric for fabricating back-gated multilayer MoS2 transistors. Excellent electrical properties such as a mobility of 15.1cm2/(Vs), an on/off ratio exceeding 107, and a hysteresis of 0.133V are achieved for samples annealed in NH3 at 400 °C for 10 min. This is caused by the NH3 annealing passivation effects that reduce defective states in the HfO2 dielectric and the interface. The capacitance equivalent thickness is only 7.85 nm, which is quite small for a back-gated MoS2 transistor and is conducive to the scaling down of the device.