Abstract
The origin of the "coffee-bean" strain contrast is studied, that is observed in the plan-view transmission electron microscopy (TEM) images of CdSe/ZnSe quantum dot structures. The samples were grown by two different methods: standard molecular-beam epitaxy at 350 degreesC and atomic layer epitaxy at 230 degreesC with annealing at 340 degreesC after the CdSe deposition. The nominal CdSe thickness ...
Abstract
The origin of the "coffee-bean" strain contrast is studied, that is observed in the plan-view transmission electron microscopy (TEM) images of CdSe/ZnSe quantum dot structures. The samples were grown by two different methods: standard molecular-beam epitaxy at 350 degreesC and atomic layer epitaxy at 230 degreesC with annealing at 340 degreesC after the CdSe deposition. The nominal CdSe thickness was above 3 ML. In situ reflection high energy electron diffraction during the growth or during the annealing shows the transition from the two- (2D) into the three-dimensional (3D) surface morphology for both samples. The coffee-bean contrast is usually assigned to three-dimensional islands which are generated after the morphological 2D/3D transition. It is found that the coffee-bean contrast in plan-view TEM images is alternatively associated with pairs of stacking faults on {111} lattice planes which are inclined against each other. The stacking faults, which are bound by Shockley partial dislocations, are preferably generated in the vicinity of the Cd-rich regions (large islands) of the CdZnSe layer where Cd concentrations of more than 40% are found. (C) 2001 American Institute of Physics.
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