2D transition metal dichalcogenides (TMDCs) have emerged as promising candidates for post-silicon nanoelectronics owing to their unique and outstanding semiconducting properties. However, contact engineering for these materials to create high-performance devices while adapting for large-area fabrication is still in its nascent stages. In this study, graphene/Ag contacts are introduced into MoS2 devices, for which a graphene film synthesized by chemical vapor deposition (CVD) is inserted between a CVD-grown MoS2 film and a Ag electrode as an interfacial layer. The MoS2 field-effect transistors with graphene/Ag contacts show improved electrical and photoelectrical properties, achieving a field-effect mobility of 35 cm2 V−1 s−1, an on/off current ratio of 4 × 108, and a photoresponsivity of 2160 A W−1, compared to those of devices with conventional Ti/Au contacts. These improvements are attributed to the low work function of Ag and the tunability of graphene Fermi level; the n-doping of Ag in graphene decreases its Fermi level, thereby reducing the Schottky barrier height and contact resistance between the MoS2 and electrodes. This demonstration of contact interface engineering with CVD-grown MoS2 and graphene is a key step toward the practical application of atomically thin TMDC-based devices with low-resistance contacts for high-performance large-area electronics and optoelectronics.
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the work function was reduced to 4.3 eV for the graphene on Ag (Figure 3f; Figure S11, Supporting Information). Considering that Ag has a relatively low work function, the presence of Ag underneath graphene leads to an n-doping effect, resulting in an upshift in the Fermi level of graphene.[15,16] This is supported by the XPS and Raman results for the MoS2/ graphene/Ag (Figure S12, Supporting Information). The XPS measurements showed that the Ag 3d5/2 and 3d3/2 peaks of the MoS2/graphene/Ag were shifted to higher binding energies than those for the Ag film. In Raman spectra, the G and 2D peaks of the MoS2/graphene/Ag were blueshifted and redshifted, respectively, compared to those of the MoS2/graphene. The shifts of XPS and Raman peaks are attributed to electron transfer from Ag to graphene.[14,38] The work function
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All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering