Preparation and electrical transport property study of MoS$_{2}$ single-layer devices on different substrates*

Micro-exfoliated MoS2 flakes on SiO2/Si substrate are identified with optical microscope first and then atomic force microscopy and Raman spectroscopy. Nanodevices are subsequently prepared by E-beam lithography. The as-prepared MoS2 devices are n-type with a high sheet resistance (typically several MOhms). As a gate voltage is applied, a large gate modulation in sheet resistance is observed. At the highest negative gate voltage, the devices remain n-type but the resistance increases by at least 4 orders of magnitude. In the meantime, the current-voltage characteristics turn from linear to non-linear. The field-effect mobility extracted from the gate voltage dependence is about 10 cm$^{2}$/Vs. To study the effect of the dielectric constant, we have developed a transfer technique that transfers entire working devices from SiO2/Si to any substrates. We have successfully applied the technique to graphene and obtained a relatively high yield. We are currently transferring MoS2 devices from SiO2/Si to strontium titanate (STO) substrate which has a much higher dielectric constant (300 at room temperature). Detailed experimental results and discussions will be presented.