Repair of Oxygen Vacancies and Improvement of HfO2/MoS2 Interface by NH3-Plasma Treatment

The effects of treating the HfO 2 gate dielectric in different plasmas (O 2 , N 2 , and NH 3 ) on the electrical characteristics of a back-gated MoS 2 transistor are investigated. It is found that the electrical properties of the device improved after HfO 2 is treated by these plasmas, in which NH 3 -plasma treatment results in the best electrical characteristics: high ON-OFF ratio of 1.26×10 7 , high extrinsic carrier mobility of 61.5 cm 2 /V·s, small subthreshold swing (SS) of 111 mV/dec, low interface-state density of 2.79 × 10 12 eV -1 ·cm -2 , and small hysteresis of 43 mV. These should be attributed to the incorporation of more N into the HfO 2 film by the NH 3 plasma to repair the oxygen vacancies and increase the k value of the HfO 2 film. Moreover, H from the NH 3 plasma effectively passivates the dangling bonds at/near the HfO 2 /MoS 2 interface, thus creating an excellent MoS 2 /HfO 2 interface.