Momentum microscopy of the layered semiconductor TiS2 and Ni intercalated Ni1/3TiS2

Abstract

The detailed electronic structure of a layered semiconductor 1T-TiS _2 and its modification in Ni-intercalated Ni _1/3 TiS _2 were studied beyond the full surface Brillouin zone by use of a momentum microscope and He-I light source on their in-situ cleaved surfaces. Clear dispersions associated with the electron Fermi surface (FS) pockets induced by the self-intercalated Ti in non-doped 1T-TiS _2 around the M points, as well as the hole FS pocket induced by the surface Ni in Ni _1/3 TiS _2 around the Γ point, were confirmed in the observed high-resolution E _B (k _x , k _y ) band cross sections. A bird’s eye view of the two-dimensional band dispersions E _B (k _x , k _y ) clarified many complex band dispersions. The experimental results are compared with first-principles band calculations performed for the bulk as well as the one monolayer (ML)-TiS _2 and surface-1ML-Ni _1/3 TiS _2 . The characteristic changes of the band dispersions near the Fermi level (E _F ) are ascribed to the contribution of the 3d states of the surface Ni atoms with the C _3v symmetry in contrast to the ‘D _3d ’ symmetry of the intercalated Ni. The importance of experimental studies of band dispersions in the full Brillouin zone is demonstrated, showing the high potential of momentum microscopy.

Keywords

• layered semiconductor
• surface electronic structure
• Fermi surface
• momentum microscopy
• angle resolved photoelectron spectroscopy
• high resolution