Spatial variations of the local density of states modified by CDWs in 1T-TaS_2-xSe_x

Spatial variations of the local density of states (LDOS) near the Fermi level have been observed on the layered dichalcogenides 1T-TaS_2-xSe_x (x = 0, 0.2, 2) for the first time. The tunneling spectra on the cleaved surfaces were measured by atomic-site tunneling (AST) spectroscopy technique at room temperature. In 1T-TaS₂, the LDOS was substantially different among the three inequivalent Ta atomic sites induced by the CDW formation. However, the surface electronic structure became homogeneous, as the Se content was increased. By substituting Se for S, the minimum position of the LDOS was systematically shifted to a higher energy side above the Fermi level.