Transfer-free, scalable vertical heterostructure FET on MoS 2 /WS 2 continuous films.

Taking into account the novel layered structure and unusual electronic properties of MoS 2 and WS 2 on the side the lack of dangling bonds between these two components and donor-acceptor linkage effects, growth of the MoS 2 /WS 2 vertical heterojunction film on the amorphous SiO 2 /Si substrate have created high demand. In this study, we reported the continuous, scalable, and vertical MoS 2 /WS 2 heterostructure film by using a sputtering without a transfer step. The WS 2 film was continuously grown on MoS 2 and eventually led to the formation of the MoS 2 /WS 2 vertical heterojunction film. Dozens of FETs fabricated on MoS 2 /WS 2 continuous heterojunction film were created on the same substrate in a single lithographic fabrication step, allowing them to be commercialized and not only used in research applications. RAMAN spectra proved the formation of the MoS 2 /WS 2 heterostructure film. In XPS measurements, it was shown that a separate MoS 2 and WS 2 layer was grown instead of the alloy structure. The polarity behavior of the MoS 2 /WS 2 heterostructure FET was found to be modulated with different drain voltages as p-type to ambipolar and finally n-type conductivity because of the transition of band structure and Schottky barrier heights at different drain voltages. Electron mobility (7.2 cm 2 V.s -1 ) and on/off ratio (10 4 -10 5 ) exhibited by the MoS 2 /WS 2 heterostructure FETs displayed a more improved electrical performance than that of individual WS 2 , MoS 2 devices. It was observed that the mobility value of MoS 2 /WS 2 FET was approximately 514 times greater than WS 2 FET and 800 times greater than MoS 2 FET. Additionally, the MoS 2 /WS 2 FET on/off ratio was larger than 2 order MoS 2 FET and 1 order WS 2 FET. The film of continuous vertical heterojunctions as in the MoS 2 /WS 2 currents in the study would be a promising candidate for nanoelectronics fields. This work demonstrated the progress towards realizing carrier-type controlled high-performance MoS 2 /WS 2 heterojunction-based FETs for future logic devices.