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

Transition‐metal dichalcogenide (TMDC) islands and thin films are grown on TiO 2 (110) via physical vapor deposition of Mo and Se and are analyzed with electron diffraction, Auger spectroscopy, and scanning tunneling microscopy (STM). Surprisingly, large, crystalline TiSe 2 patches develop on the TiO 2 surface instead of the expected MoSe 2 islands. They 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. Density‐function‐theory calculations assign the imaging contrast and the conductance doublet to tunneling into the 3p orbitals of the topmost Se layer and Ti 3d ‐related electronic states, respectively. Control experiments without Mo deposition confirm that the observed TMDC growth indeed results from a surface reaction between gas‐phase Se and Ti 3+ atoms, segregating out of the reduced TiO 2 crystal. From the unique shape and orientation of the TiSe 2 islands in the low‐coverage regime, a distinct nucleation scheme is proposed, in which the Se(3 × 1) superstructure on TiO 2 provides pinning centers for the TMDC. This article aims at increasing the awareness that Mo and Se co‐deposition does not automatically result in MoSe 2 formation, but parasitic processes may trigger the growth of other TMDCs.