Electronic structure of designed [(SnSe)1+δ]m[TiSe2]2 heterostructure thin films with tunable layering sequence

A series of [(SnSe)1+δ]m[TiSe2]2heterostructure thin films built up from repeating units ofmbilayers of SnSe and two layers of TiSe2were synthesized from designed precursors. The electronic structure of the films was investigated using X-ray photoelectron spectroscopy for samples withm= 1, 2, 3, and 7 and compared to binary samples of TiSe2and SnSe. The observed binding energies of core levels and valence bands of the heterostructures are largely independent ofm. For the SnSe layers, we can observe a rigid band shift in the heterostructures compared to the binary, which can be explained by electron transfer from SnSe to TiSe2. The electronic structure of the TiSe2layers shows a more complicated behavior, as a small shift can be observed in the valence band and Se3dspectra, but the Ti2pcore level remains at a constant energy. Complementary UV photoemission spectroscopy measurements confirm a charge transfer mechanism where the SnSe layers donate electrons into empty Ti3dstates at the Fermi energy.