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to the downshift of the state eventually leading to decrease in the bandgap.
Figure 5.9: Planar average of the weights of the CBM state in the real space
and the area of the circle represents the magnitude of the average. The unit
cell is sketched as rectangles and the dotted lines show the interface between
the and layers. As expected the CBM state is mainly composed of the
Ta d orbitals. The bandgaps for different structures is also shown on the top.
The figure is taken from the Paper-4.
Until now, the behavior of the heterostructure has only been analyzed
with only one layer. However, the scenario significantly changes when the
number of layers is increased as shown in the Figure 5.10. The figure shows
the similar plot as in Figure 5.9 with the only difference that it has two
layers as opposed to the Figure 5.9 which has one. As can be seen from the
figure that the CBM is now located mainly in the part of the heterostructure
and primarily consists of the Sn s states. A small weight in the part of the
structure represents the tunneling effect. However, as expected the tunneling
effect decreases as the number of layers is increased and almost diminishes
in going from 22 to 23. Additionally, the weights look similar in all
the structures. Therefore, the weights being similar and the diminishing of
the tunneling effect results to almost no bandgap change as the number of
layers 3.
In the last two kind of heterostructures it is found that keeping the number
of layers to one has only confinement effect on increasing the number of