Influence of Ge addition on the optical properties of As₄₀Se₅₀Ge₁₀ thin film probed by spectroscopy techniques

ABSTRACT

The thin films of As₄₀Se₆₀ and As₄₀Se₅₀Ge₁₀ were prepared on glass substrates by thermal evaporation method with thickness 1000 nm. The prepared films were amorphous in nature which was confirmed through X-ray diffraction. The chemical composition and the surface picture were obtained from energy dispersive X-ray analysis and Scanning Electron Microscopy analysis. The transmission data of the two films were collected in the wavelength range 400–1000 nm. The transmission percentage is found to be decreased whereas the absorption coefficient is increased with the Ge addition. The addition of Ge into As₄₀Se₆₀ is found to increase the refractive index and the extinction coefficient of As₄₀Se₅₀Ge₁₀ thin film. The decrease in optical band gap is explained on the basis of increase in density of states and disorderness due to Ge addition. The optical absorption in the film is due to allowed indirect transition, and the homopolar bond density is increased with Ge addition. The Raman shift observed in the two films clearly supports the optical changes due to Ge addition.

KEYWORDS:

• Amorphous semiconductor
• chalcogenides
• thin film
• optical properties
• band gap
• Raman spectra

Acknowledgments

The authors thank Department of Science and Technology (DST), Govt. of India for DST-INSPIRE Research grant and using the National Facility for Optical Spectrometry at Department of Physics and Indian Institute of Science (IISc.) for Raman measurement.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Department of Science and Technology (DST), Govt. of India for DST-INSPIRE grant (DST/INSPIRE Faculty Award/2011-IF-11)Research grant.