Type Control of MoOx/MoS2 Heterostructure Transistors by Oxidation Treatments

Molybdenum disulfide (MoS₂) has attracted much attention due to great potential applications as electronics devices. By mechanical exfoliation, few-layer MoS₂ can be obtained and made into field-effect transistors (FETs). In particular, we demonstrated that heating device under ozone exposure for several hours can change the device behaviors from natively n-type to either ambipolar or p-type. The treatments resulted in oxidation of MoS₂ surfaces to molybdenum oxide (MoO_x). Due to exhibiting high work function, MoO_x was used as an efficient hole contact. By adjusting the time and temperature of oxidation treatments, the formation of MoO_x and the work function of contact electrodes can be modulated. The MoS₂ FETs after weak and strong oxidation treatments presented ambipolar and p-type feature, respectively. In MoO_x/MoS₂ heterostructure, the devices showed the Schottky contact behaviors. The effective Schottky barrier depended on both the gate voltage and source-drain voltage. Additionally, the electrical transport and transfer characteristics of ambipolar and p-type FETs were separately explored. In this report, the oxidation treatments not only simplify the complex fabrication but also improve the diversity of applications for nanoelectronic devices.