Reflection high energy electron diffraction observation of surface mass transport at the two- to three-dimensional growth transition of InAs on GaAs(001)
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RHEED intensity of the (01) diffraction reflex as a function of time during the MBE-GI growth of InAs on GaAs(001). A total InAs coverage of 2.03 ML is delivered in consecutive cycles, each consisting of of In deposition followed by of growth interruption, while the cell shutter if kept always open. The left panels, (a) to (d), show the sequence of RHEED patterns observed at the specified times, during the growth interruption of the cycle (marked in the figure) where the total InAs coverage reaches ML. The 2D-3D transition occurs, meantime no further In has being deposited on the surface, as a consequence of the large cation surface-mass transport triggered by the elastic field and the As desorption process. The inset shows a AFM image of the 3D QDs covering the surface, at the end of the growth.
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Open squares: RHEED intensity of the (01) diffraction reflex as a function of InAs MLs deposited on GaAs(001) by MBE-GI, i.e., by consecutive cycles consisting in of InAs growth followed by of growth interruption, leaving the cell shutter open. The data points are obtained from Fig. 1, by assigning the RHEED intensity measured at the end of each cycle to the total InAs coverage reached in that cycle. Filled dots: Measured QDs number density as function of the InAs coverage. The comparison is made by normalizing at 2 ML where both QD density and RHEED intensity saturate.
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