Visualization of Tm dopant atoms diffused out of GaN quantum dots

Okuno, H.; Rouvière, J.-L.; Jouneau, P.-H.; Bayle-Guillemaud, P.; Daudin, B.
June 2010
Applied Physics Letters;6/21/2010, Vol. 96 Issue 25, p251908
Academic Journal
GaN quantum dots doped with Tm atoms and embedded in AlN have been characterized by high-angle annular dark-field imaging using a scanning transmission electron microscope. Direct visualization of individual Tm atoms in AlN layers has been achieved. We have found that besides being present in GaN dots, Tm atoms also tend to segregate at AlN barriers. The Tm distribution is related to the capping mechanism of the dots with AlN. A visibility coefficient based on locally integrated, rather than peak, intensities is introduced to determine quantitatively the number of Tm atoms in a given atomic column. Experimental and simulated images show that this visibility presents a reduced sensitivity to the defocus or to the position of the Tm atom within the thin lamella.


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