Direct imaging of the evolving Au/InSb(111) B interface

In situ high-resolution transmission electron microscopy in the profile geometry has been used to observe the evolving features of the Au/InSb(111) B-(1 × 2) interface. During Au deposition in the range between 0 monolayer (ML) and ∼1 ML coverage, the outermost Sb-trimer layer of the InSb(111) B-(2 × 2) substrate changes in contrast, presumably revealing that deposited Au atoms are partially captured into it. At ∼2 ML coverage, an unknown phase emerges on the outermost layer, beyond which it continues to grow epitaxially in an island state, causing partial disruption of the substrate. The phase is identified as Au₉In₄ alloy with a γ-brass structure determined from a digital Fourier transform diffractogram and a transmission electron diffraction pattern. The epitaxial relationship of Au₉In₄ with the substrate is given by (111)InSb∥(111) Au₉In₄ and [110] InSb∥[110] Au₉In₄. The high resolution-profile transmission electron microscopy images of this alloy agree well with the results calculated by the multislice method.