Interaction and surface photovoltage effect of MoS2 with Na deposition

초록

Using photoelectron spectroscopy (PES) with synchrotron radiation (SR), we investigated the interaction of a MoS2 surface with Na. When Na was deposited at room temperature and at low temperature (similar to 90 K), the PES data showed that both the core levels and the valence band shifted toward high binding by almost the same energies, compared with the pristine surface. This indicates that the deposited Na interacted non-reactively with MoS2, while inducing a rigid shift of the PES peaks by donating electrons to the MoS2 substrate. Deposition of sufficient amount of Na allowed the conduction band of MoS2 to be partially filled, revealing a clear Fermi edge. For Na deposition at low temperature, the Fermi edge appeared above the reference Fermi level. We attribute this to the surface photovoltage (SPV) effect generated by SR light. The SPV was measured to decrease when the sample was heated, reflecting the increasing recombination of SR-generating electron-hole pairs with increasing temperature.

키워드