Crystal Growth of Group IV Transition Metal Di- and Tritellurides

A significant amount of research has focused on the synthesis, characterization, and properties of 2D and quasi-1D layered materials since graphene’s remarkable discovery in 2004. Specifically, researchers have gravitated towards low-dimensional materials as the most promising way to construct cheaper and faster devices that can improve state-of-the-art silicon-based technology within the electronics industry. Examples include the transition metal chalcogenides, a class of van der Waals materials that exhibit unique optical and electronic properties making them excellent candidates for some next-generation electronics applications.^1-2 Both ZrTe₃ and HfTe₃ are notable transition metal chalcogenides due to their unique properties, such as the rare coexistence of both charge density wave transitions and superconductivity without physical or chemical modification.^3-6 Furthermore, ZrTe₃ exhibits an exceptionally high current density (~100 MA/cm²) in comparison to copper interconnects (~2-3 MA/cm²), the present industry standard used in conjunction with silicon-based technology.^7-8 Alternatively, studies with HfTe₃, the isostructural counterpart of ZrTe₃, have been very limited due to the difficulty in synthesizing this material and inconsistencies in the literature.^3,6,9

This talk will address these gaps in the literature and focus on novel synthetic pathways in isolating HfTe₃. Polycrystalline HfTe₃ was obtained using the solid state approach at 550 °C followed by either immediate quenching, slow-cooling, or natural cooling. We also determined that we could access single crystalline HfTe₃ at 530 °C using polycrystalline HfTe₃ as a precursor under chemical vapor transport (CVT) conditions. We further extended our work with HfTe₃ to single crystalline Hf_xZr_1-xTe₃ alloys with the ultimate goal of establishing novel synthetic routes, and exploring the possibility of tuning properties by alloying. Using the favored temperatures of single crystalline HfTe₃ (530 °C) and ZrTe₃ (850 °C), we were able to acquire specific phases of Hf_xZr_1-xTe₃ (x = 20, 40, 80) via the CVT approach. Finally, we extended our work to other transition metal chalcogenide alloys including Ti_xZr_1-xTe₂ and Ti_xHf_1-xTe₂. Using the favored temperatures of TiTe₂ (800 °C), ZrTe₂ (900 °C), and HfTe₂ (900 °C), we were able to isolate single crystalline Ti_xZr_1-xTe₂ compositions (x = 30, 50, 80) and Ti_xHf_1-xTe₂ compositions (x = 20, 40, 80) under CVT conditions.

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