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A portion of the mass spectrum collected in the atom probe during evaporation of one of the barrier layers. The shaded gray area is the range corresponding to indium atoms. A peak is clearly visible above the level of the noise.
(a) An atom map of an diameter volume reconstructed from the 3DAP data. Each dot is a detected indium atom. (b) The solid surfaces are isoconcentration plots: outside of these, the indium content is . (c) The isoconcentration surface for each of the top nine QWs in turn, showing that several have large discontinuities.
AFM images of an epilayer with similar In content and thickness as one QW layer in the MQW sample. The two circles on the right hand image each show the size of the LEAP field of view.
STEM-HAADF images of the MQW sample. (a) shows the original orientation of viewing, where the gaps are hard to distinguish. (b) shows an image in the perpendicular orientation, and at least one elongated gap (arrowed) is clearly visible. The inset shows a profile of intensity that confirms the presence of the gap in the QW layer.
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