Growth of Dichalcogenide Layers on TiO₂(110) – MoSe₂ or TiSe₂

Transition‐metal dichalcogenide (TMDC) islands and thin films are grown on TiO2(110) via physical vapor deposition and analyzed with electron diffraction, Auger spectroscopy and scanning tunneling microscopy (STM). For this purpose, Mo and Se are co‐deposited onto the surface at different temperatures and dosing conditions. Surprisingly, large, crystalline TiSe2 patches develop on the TiO2 surface instead of the expected MoSe2 islands. The former are identified by a hexagonal lattice with 3.4 Å periodicity, a unique (2×2) superstructure related to charge‐density waves and an empty conductance doublet in STM spectroscopy. DFT calculations assign the STM contrast to tunneling into the 3p orbitals of the topmost Se layer and the detected conductance doublet to maxima in the Ti 3d‐related density of states. Control experiments without Mo deposition confirmed that the observed TMDC growth is indeed the result of a surface reaction between gas‐phase Se and Ti3+ atoms, segregating out of the reduced TiO2 crystal used in our study. From the unique shape and orientation of the TiSe2 islands in the low‐coverage regime, a distinct nucleation scheme is proposed, in which the Se(3×1) superstructure on TiO2 provides pinning centers for the TMDC. Our work aims at increasing the awareness that Mo and Se co‐deposition not automatically results in MoSe2 formation, but parasitic processes may trigger the formation of other TMDCs.This article is protected by copyright. All rights reserved.