Electrical properties of ternary Ta-Te-Se single crystals

Abstract

Transition-metal dichalcogenides (TMDCs) exhibit remarkable properties, including tunable band gaps, strong spin-orbit coupling, and unique layered structures, making them excellent candidates for nanoelectronics and optoelectronic devices. Among these TMDCs, tantalum-based compounds exhibit composition-dependent structural and electrical properties, including superconductivity, charge density waves, and structural phase transitions. While selenium-rich compositions in the Ta – Te – Se ternary phase diagram have been previously explored, the tellurium-rich region has remained largely underexplored.

In this dissertation, polycrystalline and single crystal TaTexSe2-x and TaTeySe2-x compounds were synthesized using solid-state synthesis and chemical vapor transport to investigate the relationship between crystal structure and electrical properties with increasing tellurium content. In addition, the growth of chalcogen-rich TaTe1.9Se0.4 was optimized to improve reproducibility and assess limitations in compositional control. Structural and compositional characterization was performed using powder X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy, while electrical transport was measured as a function of temperature and magnetic field. Density functional theory calculations were used to support the experimental results.

This dissertation establishes composition-structure-property relationships in the tellurium-rich Ta – Te – Se system, providing a foundation for the design of next generation electronic and quantum materials.