Tailoring of Bandgap and Spin-Orbit Splitting in ZrSe_2 with Low Substitution of Ti for Zr

Tuning the bandgap in layered transition metal dichalcogenides (TMDCs) is crucial for their versatile applications in many fields. The ternary formation is a viable method to tune the bandgap as well as other intrinsic properties of TMDCs, because the multi-elemental characteristics provide additional tunability at the atomic level and advantageously alter the physical properties of TMDCs. Herein, ternary Ti_xZr_1-xSe_2 single crystals were synthesized using the chemical-vapor-transport method. The changes in electronic structures of ZrSe_2 induced by Ti substitution were revealed using angle-resolved photoemission spectroscopy. Our data show that at a low level of Ti substitution, the bandgap of Ti_xZr_1-xSe_2 decreases monotonically, and the electronic system undergoes a transition from a semiconducting to a metallic state without a significant variation of dispersions of valence bands. Meanwhile, the size of spin-orbit splitting dominated by Se 4p orbitals decreases with the increase of Ti doping. Our work shows a convenient way to alter the bandgap and spin-orbit coupling in TMDCs at the low level of substitution of transition metals.