The optical properties around fundamental absorption edge
are complicated by the occurrence of logarithmic band edges, often referred to as "Urbach tails," which give some weak absorption at the blue end of the luminous spectrum.
The position of the absorption edge
was determined by extrapolating the linear portions of [alpha] versus hv curves (see Fig.
The compilations contains K- and L x-ray transition and absorption edge
energies for all of the elements from neon to fermium and includes carefully selected and evaluated experimental data and trusted estimates obtained from state-of-the-art theoretical procedures.
Besides, the longitudinal absorption peak of the rods is close to the IR absorption edge
of the photoactive film.
It has been confirmed from Figure 4 that the optical absorption edge
of samples is shifted to 550 nm from 420 nm due to the calcination treatment, which is one of the reasons why the photocatalytic performances of calcined samples are higher than those of the corresponding uncalcined samples.
The sharp reduction in the transmittance spectrum at the energy of 3.15 eV is due to the fundamental absorption edge
that was also reported previously .
The optical band gaps of the thin films were determined from the absorption spectra near the absorption edge
. In many polymeric materials, it is usual to analyze the optical absorption at the fundamental edge in terms of band-to-band transitions theory.
The main goal of doping is a bathochromic shift, moving an absorption edge
from the UV to the visible light area, thus reducing the band gap.
For the transmission spectra shown in Figure 5, as the different deposition power of [In.sub.2][O.sub.3] target was used, the shift of the optical band edge was not really observable and a greater sharpness was noticeable in the curves of the absorption edge
. Those results suggest that the optical band gap ([E.sub.g]) values have no apparent change as the cosputtering method is used to prepare the IGZO thin films.
2 show that the absorption edge
is close to experimental wavelength 532 nm.
In particular, nanocomposites of PbS NPs directly synthesized in a hosting polymer are interesting [9-12]due to the broad absorption band and large excitonic radius of PbS NPs which allows modulating the absorption edge
from 3200 nm for the bulk, to 530 nm for very small nanocrystals .
The absorption edge
and maximum absorption strengths of the [Y.sub.2][O.sub.3]-ZnO complex oxides are shown in Table 1.