Theoretical results clearly reveal that the coupling of the incorporated S dopant with the second-nearest neighboring O atom assisted by the acceptor metals leads to the fully occupied and delocalized intermediate bands within the band gap, which originate from the SO antibonding states.
By switching off the SOC, the Dirac cone is not observable and the surface bands are degenerate within the gap (Fig. 2b), indicating the system topologically trivial.
A missing-post defect is deliberately introduced in the photonic crystal, opening a narrow pass band within the band gap.
Since the energy level of Ag impurity always lie near the valance band within the band gap, therefore, any change in the valance band position with composition will also shift the position of Ag level in accordance with the Gross et al. and results in the emission tunability in the PL spectra.
Band-gaps with narrow bands of allowed states within the gap were also considered.
Actually, the generally accepted picture of the electronic energy bands in a-Si is quite similar to that of c-Si, except for the presence of significant band tails and localized states within the gap, both originating from defects in the a-structure [13].
With the indirect band gap, the SOC gap cannot be the bulk band gap.
The UV vis absorption spectrum showed anEgapvalue of 3.31 eV, which was ascribed to the presence of intermediary energy levels between the valence band and conduction bands (deep and shallow holes) within the band gap.
Additional absorption feature attributed to Cr band formation within the fundamental band gap of TiO2 is also displaced towards visible.
In particular, for CdSe NCs the particles were covered with ZnS [15, 17] to establish a core/shell system, where the band gap of the core lies energetically within the band gap of the shell material and the photogenerated electrons and holes are mainly confined inside the CdSe.
