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

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.