Structure, composition, and strain profiling of Si/SiO2 interfaces

摘要

Recently, the scanning transmission electron microscope has become capable of forming electron probes of atomic dimensions. This makes possible the technique of Z-contrast imaging, a method of forming incoherent images at atomic resolution having high compositional sensitivity. An incoherent image of this nature also allows the positions of atomic columns in a crystal to be directly determined, without the need for model structures and image simulations. Furthermore, atomic resolution chemical analysis can be performed by locating the probe over particular columns or planes seen in the image while electron energy loss spectra are collected. The authors present images of the Si/SiO2 interface showing no crystalline oxide, compositional profiles across a nitrided sample at 2.5 angstrom resolution showing an extended sub-stoichiometric zone, and strain profiles at a rough interface showing static rms displacements approximately 0.1 angstrom extending 10 angstroms into the crystalline Si.