Charge transfer in (PbSe)_1+δ(NbSe₂)₂and (SnSe)_1+δ(NbSe₂)₂ferecrystals investigated by photoelectron spectroscopy

Abstract

Rotationally disordered, layered (PbSe)[Formula: see text](NbSe₂)₂ and (SnSe)[Formula: see text](NbSe₂)₂ ferecrystal heterostructures, consisting of stacked two-dimensional bilayers of either PbSe or SnSe alternating with two planes of NbSe₂, were synthesized from modulated elemental reactants. The electronic structure of these ternary systems was investigated using x-ray photoelectron spectroscopy and compared to the binary bulk compounds PbSe, SnSe and NbSe₂. The Pb and Sn core level spectra show a significant shift towards lower binding energies and the peak shape becomes asymmetric in the ferecrystals, while the electronic structure of the NbSe₂ layers does not change compared to the bulk. This is interpreted in terms of an interlayer interaction in the form of a charge transfer of electrons from PbSe or SnSe into the NbSe₂ layers, which is supported by valence band spectra and is consistent with prior results from transport measurements.