They are originated from the defects on MWCNT at sidewalls, which convey abundant reaction sites.
Thus, non-radiative recombination at sidewalls in such structures is weak, and etching can be done through the active region.
In addition, after the etching processes, the Si NWs appear like cylinders oriented along [001] direction without specific facets at sidewalls.
Band structures of the less favored, but possible, adsorption mechanisms, i.e., at sidewalls other than the {110} facet (Figure 3), are shown in Figure 4.
Higher threshold as compared to the MRs with D = 2 μm is probably due to higher scattering losses and increased contribution of non-radiative recombination at sidewalls.
Under different conditions, thus, dot formation was found to occur at different substrate locations, such as in the center of pits [7 17], in the middle of grooves [4 6], at sidewalls [4 6], or even at edges or ridges [1, 2, 10, 12, 15, 16] of the pattern structures.
However further increase in d results in a rapid growth of the generation threshold, which can be explained by increased non-radiative recombination at sidewalls (waveguide width decreases to 0.4 μm) as well as by enhanced light scattering at microring wall roughness.
Without external electric field, the HOMO and LUMO charges for pristine capped (5, 5) C-SWNT are localized at the sidewall of the tube, not at the cap, which is agreement with the available theoretical work [5, 6].
Moreover, shear micro-cracks were predominantly observed at the sidewall whereas tensile micro-cracks were dominant at regions around the roof of the inverted U-shaped opening.
Then in Fig. 4h, the two tetrahedron sections are inserted to form the two separate huts connecting the nanowires sitting at the bottom of the rib valley and the pyramids at the sidewall.
