Structural and optical parameters of films deposited on quartz substrates by laser ablation

Abstract

ZnS x Se 1−x laser ablated films deposited on quartz substrates have been studied in order to obtain information on their structural and optical properties as a function of sulphur concentration (x ). Transmittance and reflectance spectra at room temperature were carried out to obtain the energy gap modulation, the absorption coefficient and refractive index. By using the Newton-Raphson algorithm, the values of the real part of the refractive index in the transparent region were deduced including the effect of non-uniformity of the film thickness. The wavelength dependence of n was extrapolated for the weak and medium absorption range by means of two different models: the classical Cauchy formula and the single effective oscillator model proposed by Wemple and Di Domenico. From the latter theory, two physical parameters known as oscillator energy and oscillator strength, respectively, were obtained. These parameters have been related to the optical gap and structural properties of the deposited alloys. In the strong absorption region, the absorption coefficient and the optical gaps were calculated for each x -value. A quadratic trend was found for the x -dependence of the band gap, in agreement with the corresponding bulk alloy.

Bandgap engineering by substitution of S by Se in nanostructured ZnS1−xSex thin films grown by soft chemical route for nontoxic optoelectronic device applications

“…77-2100 for ZnS, and JCPDS card No. 80-0021 for ZnSe [17,29], wherein the broad peaks indicate nanostructured nature of the thin films. The shift in the peak positions towards the higher 2Â values for (1 1 1) plane (from 27.27 • to 28.50 • ) and (2 2 0) plane (from 46.00 • to 47.15 • ) was observed with increase of sulphur content in the films (decrease in x).…”

“…Furthermore, electron affinity and electrical properties of these films can be tuned by changing the ratio of S to Se, which helps to enhance the blue response to the material [9]. Earlier, thin films of ZnS 1−x Se x have been prepared using molecular beam epitaxy [10,11], atomic layer epitaxy [12], high pressure sputtering [13], metal organic vapor epitaxy [14,15], metal organic chemical vapor deposition (MOCVD) [16], laser ablation [17], close space evaporation [6], spray pyrolysis [18], epitaxial growth [19], thermal evaporation [20], Successive Ionic Layer Adsorption and Reaction (SILLAR) [21], and soft chemical route technique [22][23][24], etc. ZnSe nanowires were synthesized by Sublimation Sandwich method (SSM) [25] and facile thermal vaporation method [26], Theoretical studies have also been carried out, wherein, Yu et al [27] performed ab initio calculations of the structural, dielectric and lattice properties of ZnX (X = O, S, Se and Te).…”

Optical parameters of amorphous arsenic triselenide multilayers prepared by spin coating

“…Although these factors have been kept minimal, however, the refractive index seems to be independent of the thickness and the number of layers. The experimental results have been fitted by the Sellmeier formula with one oscillator, which is given by [10][11][12][13][14]:…”

Optical Properties

“…The n(E) and k(E) curves for c-ZnS x Se 1Àx have also been determined from optical transmittance measurements [291]. Ozaki and Adachi [292] carried out MDF analysis to obtain a closed analytic formula for the optical constants of c-ZnS x Se 1Àx as a function of x.…”