Improved subthreshold swing of MoS₂ negative-capacitance transistor by fluorine-plasma treatment on ferroelectric...

In this work, the ferroelectricity of hafnium zirconium oxide (Hf_0.5Zr_0.5O₂, HZO) is enhanced by fluorine (F)-plasma treatment, which is used to fabricate MoS₂ negative-capacitance field-effect transistor. Measurements show that the subthreshold swing of the transistor is significantly reduced to 17.8 mV dec^-1 over almost four orders of output current, as compared to its counterpart without the F-plasma treatment (37.4 mV dec^-1). The involved mechanism is that during the F-plasma treatment, F atoms can be incorporated into the HZO bulk to passive its oxygen vacancies and interface traps, thus forming robust Zr-F and Hf-F bonds. Therefore, the F-plasma-treated HZO film exhibits much less oxygen vacancies than the untreated HZO film, which is beneficial to enhancing the amplification effect on the surface potential of the MoS₂ channel during the NC operation.