Visualizing the nucleation of InN from arrays of In/In₂O₃ core/shell nanostructures

Understanding the atomic-scale mechanisms governing the nucleation and growth of indium nitride (InN) and related alloys is critical for tailoring their structural and functional properties in advanced electronic and optoelectronic devices. Using real-time environmental transmission electron microscopy (E-TEM) in conjunction with Gibbs free energy calculations, we elucidate the mechanisms for NH₃-assisted nucleation and growth of InN from arrays of In-In₂O₃ core-shell nanostructures. During initial annealing of the core-shell nanostructure arrays in vacuum, fracture of the oxide shells, followed by out-diffusion of liquid indium and formation of  “satellite” indium nanostructures is observed. Upon heating to moderate temperatures, the largest indium nanostructures evaporate, leaving behind nearly-empty oxide shells. Finally, introduction of NH₃ facilitates growth of faceted InN atop the In₂O₃ shells. High-resolution transmission electron microscopy suggests an InN growth mechanism consisting of NH₃-induced reduction of In₂O₃ to metallic indium followed by layer-by-layer growth of InN.  We compare the free energies for formation of InN from In₂O₃, with and without the formation of intermediate indium phase. We also discuss the role of the In/In₂O₃ interface in facilitating NH₃ decomposition and InN growth.