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ADF-STEM Imaging of Strained GaN0.045As0.955 Epitaxial Layers on (100) GaAs Substrates
Published online by Cambridge University Press: 01 February 2011
The annular dark field (ADF) image contrast of a 0.92% tensile strained GaN0.045As0.955 layer on GaAs substrate was studied with a scanning transmission electron microscope (STEM) as a function of ADF detector inner semi-angles ranging from 28 mrad to 90 mrad. The GaN0.045As0.955 layers were brighter than the surrounding GaAs for the values of ADF detector semiangle up to 65 mrad, and the measured contrast decreased with increasing ADF detector inner semi-angle. For a 37 nm thick specimen, the GaN0.045As0.955 intensity is about 13% higher than that of GaAs in the 28 mrad ADF detector inner semi-angle. Multislice simulations show that the displacement around substitutional N atoms plays an important role in the observed ADF-STEM contrast, while the contribution to the contrast due to misfit strain between GaN0.045As0.955 and GaAs is small.
- Research Article
- MRS Online Proceedings Library (OPL) , Volume 982: Symposium KK – Electron Microscopy Across Hard and Soft Materials , 2006 , 0982-KK01-03
- Copyright © Materials Research Society 2007