Tailoring the phase transition pathway of Ag2Te nanowires via surface confinement: an in situ transmission electron microscopy study

Abstract

Controlling the phase transition of Ag₂Te is crucial for its application in functional devices since the structural change significantly influences its properties. However, convenient and precise control over this process remains challenging. This study proposes a carbon-encapsulation strategy to tailor the phase transition behavior of Ag₂Te nanowires. In situ heating experiments reveal a novel transition from monoclinic Ag₂Te to hexagonal Ag₅Te₃ at 180 °C and to hexagonal Te at 200 °C. Compared to the conventional monoclinic-to-fcc transition at 150 °C, this altered pathway is attributed to the interfacial interaction between the carbon shell and Ag₂Te nanowire, which may raise the energy barrier for Ag diffusion and lattice reconstruction. In contrast, partially exposed nanowires exhibit rapid surface diffusion and reconstruction. Using this strategy, an Ag₂Te–Te heterojunction is fabricated in situ, exhibiting a transition from ohmic to rectifying characteristics, as supported by DFT calculations. Our findings demonstrate the potential of the carbon-encapsulation strategy for phase modulation of Ag₂Te nanostructures, offering valuable insights for structural design of novel Ag₂Te-based nanodevices.