Analysis of partially oxidised epitaxial silicon mono-layers on germanium virtual substrates using aberration corrected scanning transmission electron microscopy

We report the application of aberration corrected STEM imaging to study the interface structure of a partially oxidised epitaxial-Si passivation layer, nominally 2 mono-layers thick, deposited on a Si(001)/Ge virtual substrate. HAADF imaging revealed evidence of 1-2 mono-layers of crystalline Si between the Ge virtual substrate and overlying SiO2. An interface roughness of 1-2 mono-layer steps was also apparent between the epitaxial-Si and Ge virtual substrate. The total thickness of the residual crystalline Si and overlying SiO2 suggests that the initial epitaxial-Si layer may have been 1-2 mono-layers thicker than the nominal value.