Intensity profiles plotted in the directions perpendicular to eac

Intensity profiles plotted in the directions perpendicular to each set of moiré fringes

(not shown here) depict a separation of 0.6 nm in between correlated fringes, changing the abcabc periodicity of crystal to a’bc’da’bc’d. The GaAs regions above and under the GaAsBi layers are shown for reference. Figure 5 Numerical moiré find more fringe maps obtained from HRTEM images. The maps correspond selleck chemicals llc to (a) region I (bottom) and (b) region II (top). Red and green fringes correspond to ordering on the two 111B planes. Dashed lines in (a) and (b) mark the beginning and end of the GaAsBi layer, respectively. The ordering maps in region I show both variants coexisting in similar proportions over the whole GaAsBi layer. In addition, the estimated LRO parameters gave values of 1 for both 111B families. However, in region II of S100 with lower Bi content, the ordering is irregular, with lower LRO parameter (0.4 to 0.8) regions where one 111B family predominates and others where little ordering is present. Discussion The ordering within the GaAs matrix is a phenomenon that occurs on 111 planes due to the distribution of atomic scale compressive and tensile strain sites. This distribution of solute atoms within selleck products the solvent matrix is believed to be responsible for enhanced solubility in GaAsBi [6] and GaInP [31]. However, growth of GaAsBi under a (2 × 1) reconstruction leads to anisotropic

growth and a constantly increasing density of steps that eventually results in an undulating surface [9]. The undulations present compression (troughs) and tensile (peak) zones on the macroscopic scale. These macroscopic compressive and tensile zones occupying multiple near surface lattice sites offer a much more attractive strain relaxation centre compared to the individual atomic sites that lead to ordering. In S100, this switching point between preferred Bi incorporation sites leads to an evolution from CuPtB ordering to phase separation at approximately 25 nm. There is clearly a correlation between the degree of ordering and the Bi content, i.e. more ordering occurs

Cytidine deaminase in material with a higher Bi content. The CuPt ordered GaAsBi provides an attractive lattice site for Bi in the GaAs matrix. The undulation peaks offer attractive surface sites for Bi on a GaAs matrix, where a high local density of surface Bi exists on an undulation peak. Furthermore, the compressive troughs are highly unattractive surface occupancy sites for Bi. Thus, the overall Bi surface population is effectively halved and the Bi content of the GaAs matrix is subsequently reduced. The reduction in incorporation causes an excess of surface Bi and may result in Bi droplet formation. This would suggest that alloy clustering is only the favourable mechanism for Bi incorporation into the GaAs matrix when the growth surface is highly undulating.

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