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.
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 [1].
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.
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.
The
absorption edge and maximum absorption strengths of the [Y.sub.2][O.sub.3]-ZnO complex oxides are shown in Table 1.