The established equation from cross-plot helped in modeling the brittleness and identifying high BI areas in the study area (Fig. 13).
In addition, the above result proves that Bi nanowire growth is not driven by the thermal evaporation of Bi atoms during annealing; if this were the case, then Bi nanowire density should be independent of Bi film area.
The Bi nanowire density increases as the size of Bi film area increases and as the difference in thermal expansion coefficients between the substrate and the Bi film increases, confirming that compressive stress acts as the driving force for Bi nanowire growth by the OFF-ON method.
In this sense, Bi film area is another parameter that determines the Bi nanowire density.
If the compressive stress hypothesis is reasonable, then a larger Bi film area should result in a higher density of Bi nanowires, because the compressive stress is generally less relieved at the center of a film and more released at the edges of the film.
However, the intensity distribution suggests the presence of two different compositional volumes in the particle: a Bi-rich one with trapezoidal shape surrounded by a less Bi-rich area.
The detail of an undistorted region in the GaAs layer and distorted anion-cation dumbbells in a Bi-rich area at higher magnification are included as an inset in the same image.
Indeed, we found that the density of Bi nanowires at the edge is higher in the factor of 1.3 than that at the center, and the total density increased as the Bi film area increased after annealing at 270°C for 10 h (see Figure 3e).
The BI mean area in condyles without MSCs was 112.692 μm (±95.787 μm), while that for condyles with MSCs was 315.501 μm (±113.547 μm); this difference was statistically significant (P = 0.0389).
Second, the effect of Bi film areas, where the Bi nanowires are grown, on nanowire density was addressed.
