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

Abstract

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 (Pm1 space group, no. 164) with the lattice parameters a = 3.7668(4) Å and c = 6.4918(10) Å. The TiTe₂ crystal showed metallic behavior with decreased resistivity upon cooling and a relatively low resistivity value (4.39 × 10⁻⁴ Ω 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 metal–semiconductor contacts in 2D semiconductor devices.