Size-dependent phase evolution and electrical properties of Cu2-xTe thermoelectric nanofilms

Low-dimensionalization has emerged as a novel approach for thermoelectric material modification. Cu2-xTe has been proposed as promising thermoelectric material, yet its structure and properties upon lowdimensionalization remain largely unknown. Nanofilms with varying thicknesses from 20 nm to 340 nm were synthesized by RF magnetron sputtering, and their structures were characterized using high-angle annular darkfield scanning transmission electron microscopy (HAADF-STEM) and X-ray diffraction (XRD). By modulating thickness of the nanofilms, we observed a novel layered structure of Cu2-xTe and formation of three roomtemperature stable phases and their size-induced evolution. Furthermore, we demonstrate that the electrical properties of nanofilms are significantly modulated by size control. Since, we have achieved direct size-induced control over the structure and electrical properties of Cu2-xTe nanofilms.