Fig. 5

Spatially confined doping in photo-switchable superlattices. Transfer characteristics (I_DS–V_GS) of devices based on graphene and MoS₂ superlattices. I_DS is the drain current, and V_GS is the gate potential. a Schematics of the experiment. I_DS–V_GS characteristics are measured for: (1) The graphene device covered by the SP film; (2) After UV light irradiation over the whole superlattice, which triggers the SP→MC isomerization; (3) After green light irradiation in a well-defined area of the active layer, which triggers the MC→SP isomerization in the irradiated area. Gold contacts are schematically drawn in yellow, graphene in dark gray; the substrate in blue; the SP layer in semi-transparent red; the MC layer in semi-transparent green. b Trace 1 (red): graphene covered by the SP layer, trace 2 (blue): graphene/MC after UV irradiation over the whole flake. The arrow highlights the negative shift in the threshold voltage accompanying the SP→MC isomerization, indicative of n-type doping. c Trace 3 (green solid line): graphene/MC+SP, obtained by local irradiation with green light. Traces 1 and 2 are replotted. Details about the UV and green light irradiation are given in the Methods section; the transfer curves were measured applying a drain-source voltage V_DS = 10 mV. Channel length L = 8.9 µm and width W = 1.0 µm