Ultraviolet-light-driven enhanced hysteresis effect in graphene-tungsten disulfide heterostructures

The discovery of two-dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) and their exceptional properties have shown prodigious advancement in the field of digital electronics. Here we report a large hysteresis effect by constructing graphene-tungsten disulfide heterostructure (GWH), where the semiconducting WS2 acts as a channel in field effect transistor geometry while graphene works as charge trapping interfacial layer. Raman spectra illustrates the characteristics of high quality graphene and the WS2 films. The transport characteristics as a function of gate voltage show the usual behavior of graphene and WS2 transistor. However, that of GWH are significantly exhibiting hysteresis effect after UV irradiation. The characteristic curves show the hysteresis with relatively small window (ΔV) of ∼12 V at an operating voltage of 0.5 V and shows astonishing tunability for increasing operating voltages. The value of ΔV is increased up to ∼116 V at the drain source voltage of 2 V with great stability. The charge trapping layer 'graphene' works for charge retention and therefore makes the resulting heterostructures capable of operating as a hysteresis device. These results offer the realization of advanced heterostructural devices for nonvolatile memory applications.

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