Element- and Site-Specific Many-Body Interactions in Few-Layer MoS2 During X-Ray Absorption Processes

Few-layer MoS2 is a promising 2D material for nano-electronic device applications. However, the performance of these devices is often deteriorated. One of the reasons is that the electronic properties are influential to the many-body effects such as excitonic effects and Anderson orthogonality catastrophe (AOC) which could renormalize the band-dispersion and density-of-states(DOS). Hence, the authors investigate the effect of many-body interactions on MoS2 device performance by using X-ray absorption spectro-microscopy (mu-XAS) on a few-layer MoS2 transistor in operation, through the application of gate-bias or contact with a metal. The results show a significant peak shift in mu-XAS spectra while varying the gate-bias. The applied negative gate-bias induces more holes which attracts excited electrons resulting strong many-body interactions followed by Fermi level shift. This effect is discussed with the aid of XAS-Auger electron phenomena. However, the AOC contribution in XAS peak-intensity is ignored since the bands around the energy-gap in MoS2 are relatively flat and the DOS is empty above Fermi level (unlike graphene). The authors observe a redshift in photon energy near the MoS2/metal-electrode interface due to charge transfer ensuring carrier-doping induced through metal-contact. These observations provide significant insight into element- and site-specific many-body interactions in MoS2 tunable by gate-bias or contact with a metal.