We have fabricated and characterized suspended single-layer MoS2 devices to investigate the substrate effect on the electrical properties of MoS2. The MoS2 devices were fabricated on Si/SiO2 first by using e-beam lithography and were suspended by etching away half of the SiO2 layer with buffered oxide etchant and drying them with critical point dryer. Compared with SiO2 substrate-supported devices, the suspended devices show 2-10 times of mobility and on/off ratio improvement. While measuring the electronic properties, we observed that the suspended devices were annealed by joule heating and showed the performance improvement, whereas the supported devices did not. Our observations reveal that MoS2 devices are substrate-sensitive in their electrical properties and that proper substrates and cleaning is necessary for the optimal device performance.

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