Single-crystal growth of layered metallic materials of TiTe₂ based on a polytelluride flux method

Layered metallic transition metal dichalcogenides (TMDs) with bonding-free surfaces and weak Fermi-level pinning properties have exhibited potential application as electrode materials in two-dimensional (2D) semiconductor devices. However, various TMDs metallic materials are still limited in certain areas, especially due to the lack of a low-work function (<4.5 eV) counterpart. Herein, we report a polytelluride flux growth method for TiTe2 single crystals and determine the work function of this IVB group metallic TMD for the first time. The obtained crystal adopts a typical 1T-type structure (P<(3)over bar>m1 space group, no. 164) with the lattice parameters a = 3.7668(4) angstrom and c = 6.4918(10) angstrom. The TiTe2 crystal showed metallic behavior with decreased resistivity upon cooling and a relatively low resistivity value (4.39 x 10(-4) Omega cm) at room temperature. By ultraviolet photoelectron spectroscopy, the work function of TiTe2 was determined as 4.31 eV, which is much smaller than the reported data of other metallic TMDs. Our study demonstrates the interesting work function data of 1T-TiTe2, which can be utilized to make excellent metalsemiconductor contacts in 2D semiconductor devices.