Effect of compositional variations on the optical properties of Sb–Ge–Se thin films

Abstract

Compositional dependences of the optical and physical properties of as-deposited amorphous SbxGe25−xSe75 films (x = 0, 5, 10, 15 and 20 at%), prepared by thermal evaporation, have been studied. The refractive index, n, and film thickness, d, have been determined from the upper and lower envelopes of the transmission spectra, measured at normal incidence, in the spectral range from 400 to 2500 nm. An optical characterization method for uniform films based on Swanepoel's ideas has been employed, and it has allowed us to determine the average thickness, , and the refractive index, n, of the films, with accuracies better than 1%. It has been found that the refractive index of the SbxGe25−xSe7 samples increases with increasing x, over the entire spectral range, which is related to the increased polarizability of the larger Sb atomic radius 1.38 Å compared with the Ge atomic radius 1.22 Å. The dispersion parameters such as E0 (single-oscillator energy) and Ed (dispersive energy) were discussed in terms of the single-oscillator Wemple–DiDomenico model. The absorption coefficient, α, and therefore the extinction coefficient, k, have been determined from the transmittance and reflectance spectra in the strong absorption region. The optical energy gap is derived from Tauc's extrapolation and a decrease in with increasing Se content. Finally, in terms of the chemical bond approach, cohesive energy has been applied to interpret the decrease in the glass optical gap with increasing Sb content in SbxGe25−xSe75.

Effect of antimony addition on the thermal and electrical-switching behavior of bulk Se–Te glasses

“…Though the measurement of E g has not been performed in the present work, E g has been reported to decrease with increasing antimony content in a similar Se-Te-Sb system [38], and in other glassy systems such as Se-Sb [39] and Sb-Ge-Se [40]. Further, the number of weakest Te-Te bonds increase with Sb content in the Sb x Se 55Àx Te 45 (2 6 x 6 9) system, particularly for x > 4.…”

Thickness dependence of structural and optical properties of cadmium iodide thin films

“…8 further shows that, the absorption edge shifts toward lower energy region with increasing film thickness. It is known that, pure CdI 2 compounds have a sharp absorption edge [12,[29][30][31].…”

Optical characterization of polycrystalline ZnSe1−xTex thin films using variable angle spectroscopic ellipsometry and spectrophotmetery techniques

“…The optical constants (n, k) and thickness of ZnSe x Te 1 À x thin films have been obtained in litratures from reflectance (T) and transmittance (R) measurements using the spectrophotometery technique [7][8][9][10][11][12][13] and from psi (ψ) and delta (Δ) using the spectroscopic ellipsometry (SE) technique [14][15][16][17][18][19]. These methods represent powerful techniques to investigate the optical response of materials.…”