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Journal of Physical Studies 24(3), Article 3705 [9 pages] (2020)
DOI: https://doi.org/10.30970/jps.24.3705 OPTICAL PROPERTIES OF CdSe THIN FILMS ANNEALED IN THE CdCl2 ATMOSPHERE
H. A. Ilchuk1, A. I. Kashuba1
1Lviv Polytechnic National University, 12, S. Bandera St., Lviv, UA–79013, Ukraine
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II-VI binary semiconducting compounds belong to the cadmium chalcogenide family (CdS, CdSe, CdTe). They are promising materials for photovoltaic and sensor applications (in solar energetics, gases sensors). CdTe and CdSe are good photovoltaic materials due to their high absorption coefficient and nearly optimum bandgap energy for the efficient absorption of light and conversion into electrical energy. In particular, CdS is the most used material as an optical window in heterojunction solar cells based on CdTe and CIGS. CdSe thin films have a great potential for fabricating solar batteries of high efficiency, photoreceivers, light-emitting diodes, nanosensors, biomedical devices for image processing, thin film transistors, and other optoelectronic devices for solar hybrid systems.
The results of experimental studies of the optical properties of CdSe thin film annealed in the atmosphere of CdCl${}_{2}$ are presented. The synthesis of CdSe thin film was carried out by the quasi close-space sublimation method on an ITO/glass substrate. The quality of the obtained film was studied using scanning electron microscopy and energy-dispersive X-ray analysis. Optical transmission and reflection spectra were obtained experimentally. Optical constants and the bandgap of the films under study have been determined ($\textit{E}_{g}= 1.67$ eV). Optical properties (refractive index $\textit{n}$($λ$), absorption coefficient $α$($λ$), extinction coefficient $\textit{k}(λ$) and dielectric functions $ε(λ$)) of CdSe thin films and thickness ($\textit{d}$) can be determined from the transmission spectrum. The dispersion of the refractive index was explained using a single oscillator model. The single oscillator energy and dispersion energy are obtained from fitting. Optical parameters of the films were determined using the Cauchy, Sellmeier and Wemple models. The material optical parameters such as normalized integrated transmission, zero and high-frequency dielectric constant, density of state effective mass ratio were also calculated.
Key words: thin film, optical bandgap, optical functions, transmission, dielectric functions.
