Abstract
In this paper, relativistic carrier mobilities and photoconduction properties in graphene/MoS2 heterostructure (GM-HS) are mapped via photoconductive scanning noise microscopy with a conducting nanoprobe. Graphene on MoS2 (HS) regions shows two-times reduced sheet conductance (GSh) without a significant increase in trap densities (NT) compared to that in graphene on SiO2 (Gr) regions, due to the electron-doping in graphene by underlying MoS2. Interestingly, both regions exhibit GSh independent of NT, which indicates that the relativistic nature of graphene is preserved in the overall GM-HS. The mobility map is obtained from conductivity maps at different gate biases, showing a rather low mobility in HS regions compared to that in Gr regions. Notably, the overall film exhibits a sharp increase in mobility at low carrier densities, as previously reported in graphene having relativistic carriers. Under the illumination with photon energies above the MoS2 bandgap, HS regions exhibit pronounced negative photoresponses originating from the injection of photo-excited electrons from MoS2 to graphene. Unexpectedly, under the illumination with photon energies below the MoS2 bandgap, HS regions exhibit marginally negative photoresponses, possibly due to additional carriers de-trapped from trapping sites in MoS2. Interestingly, photoconductance is independent of phototraps, indicating that the relativistic photoconduction is preserved in GM-HS.

http://dx.doi.org/10.1002/smtd.202501783