Some optical properties of Se-Ge-As amorphous chalcogenide glasses

Optical-constant calculation of non-uniform thickness thin films of the Ge10As15Se75 chalcogenide glassy alloy in the sub-band-gap region (0.1–1.8eV)

“…This peak almost invariably occurs at a value of the modulus of the scattering vector of %1 A Ê À1 in amorphous chalcogenides. The absence of FSDP in the ternary alloy under study is certainly noteworthy (this signi®cant fact has also been found by El-Samanoudy and Fadel [11,12], with different amorphous Ge 25Àx As x Se 75 ®lms), in clear contrast to the binary glassy alloy, Ge 25 Se 75 (see Fig. 1(b)).…”

“…Finally, it should be mentioned that there is a difference of %4% between the Tauc gap derived in the present study, and that reported by El-Samanoudy and Fadel [11] for layers of the same chemical composition, 1.81 eV. This difference could be explained considering that in [11], the calculation of the absorption coef®cients is carried out only approximately, by use of the well-known Lambert±Beer law: I I 0 exp(-d), where I and I 0 are the intensities of the transmitted and incident beams, respectively. However, this expression does not take into account, obviously, the multiple re¯ections at the three interfaces of the optical system analyzed, which can lead to serious errors in the values obtained for .…”

“…The value for the slope parameter, E e , obtained from the corresponding -values, is %71 meV. Finally, it should be mentioned that there is a difference of %4% between the Tauc gap derived in the present study, and that reported by El-Samanoudy and Fadel [11] for layers of the same chemical composition, 1.81 eV. This difference could be explained considering that in [11], the calculation of the absorption coef®cients is carried out only approximately, by use of the well-known Lambert±Beer law: I I 0 exp(-d), where I and I 0 are the intensities of the transmitted and incident beams, respectively.…”

“…5 for the present representative, as-deposited thin-®lm sample of the Ge 10 As 15 Se 75 alloy. Furthermore, the values of the absorption coef®cient for the As 30 Se 70 [15] and Ge 25 Se 75 [16] binary compositions, as well as the corresponding optical-absorption edge for the same ternary composition under study, reported by El-Samanoudy and Fadel [11], are also shown in Fig. 5, for the purpose of comparison.…”

“…Optical-absorption edge for the representative Ge 10 As 15 Se 75 sample, and the corresponding absorption edges for the As 30 Se 70 and Ge 25 Se 75 binary alloys. Also shown is the absorption edge taken from [11], for the same ternary chalcogenide composition studied in this work. The inset shows the extinction coefficient, k, as a function of photon energy.…”