Optical properties of amorphous (As0.33S0.67)100−xTex (x=0, 1, 5 and 10) chalcogenide thin films, photodoped step-by-step with silver

• Published in: Journal of non-crystalline solids Vol. 354; no. 2-9; pp. 503 - 508
• Main Authors: Márquez, E., González-Leal, J.M., Bernal-Oliva, A.M., Jiménez-Garay, R., Wagner, T.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.01.2008; Elsevier
• Subjects: Amorphous semiconductors; Amorphous semiconductors; glasses; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Optical spectroscopy; Photo-induced effects; Physics; 78.66.Jg; Optical spectroscopy; 78.20.Ci; Photo-induced effects; Amorphous semiconductors; Envelope function; Refractive index; Doping; Silver additions; Arsenic Tellurium Sulfides Mixed; Chalcogenides; Thin films; Energy gap; Chemical composition; Absorption spectra; Vacuum evaporation; Optical constants
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2007.06.087

We have analysed in detail the effect of silver-content on the optical properties of Ag-photodoped amorphous (As0.33S0.67)100−xTex (with x=0, 1, 5 and 10at.%) chalcogenide thin films; the chalcogenide host layers were prepared by vacuum thermal evaporation. Films of composition Agy[(As0.33S0.67)100−xTex]100−y, with y≲18at.%, were successfully obtained by successively photodissolving about 20- or 40-nm-thick layers of silver. The optical constants (n,k) have been accurately determined by an improved envelope method [J.M. González-Leal, R. Prieto-Alcón, J.A. Angel, D.A. Minkov, E. Márquez, Appl. Opt. 41 (2002) 7300], based on the two envelope curves of the optical-transmission spectrum, obtained at normal incidence. The dispersion of the refractive index of the Ag-photodoped chalcogenide films is analysed in terms of the Wemple–DiDomenico single-effective-oscillator model: n2(ℏω)=1-EoEd/(Eo2-(ℏω)2), where Eo is the single-oscillator energy, and Ed the dispersion energy. We found that the refractive index of the Ag-doped samples strongly increases with the Ag-content, whereas the optical band gap, Egopt, decreases also notably. For instance, in the particular case of x=10at.%, the largest Te-content, Egopt decreases from 2.17 down to 1.67eV. It should also be mentioned that, in the case of the undoped samples, when the Te-concentration increases from zero up to 10at.%, the value of Egopt decreases from 2.49 down to 2.17eV.