Low temperature synthesis of copper telluride nanostructures: phase formation, growth, and electrical transport properties

Abstract

We propose a low cost solution-based approach to synthesize various low dimensional copper telluride (Cu-Te) nanostructures. By precisely controlling different ethylenediamine (EDA) ratios in a reaction solution, we are able to control the phases and morphologies of Cu-Te nanostructures from Te/Cu core–shell nanowires at a low volume fraction of EDA <8%, Cu₃Te₂ nanowires at the volume fraction of EDA between 8% and 24%, Cu₂Te nanowires and nanobelts at the volume fraction of EDA between 24% and 48%, to Cu₂Te/Cu core–shell nanobelts at the volume fraction of EDA over 48%. The formation mechanism is attributed to varied tendency of different coordinative copper complexes. In situ heating XRD results and TEM observations of the Cu₂Te nanowires reveal the phase transition from hexagonal P3m1, hexagonal P6/mmm to cubic structure at annealing temperatures of 25 °C, 500 °C to 600 °C, respectively. The lack of back gate dependence demonstrates the metallic feature of Te/Cu core–shell nanowire while obvious p-type behavior can be found for Cu₂Te nanowire with an on/off ratio of ∼10⁴ and the field effect hole mobility of ∼18 cm² V⁻¹ s⁻¹. These Cu-Te nanostructures exhibit controllable transport behaviors from metallic to semiconducting natures with different EDA volume fractions and have promising applications in electronics such as nonvolatile memory, photodetectors, and solar cells.