Abstract
The optical transmission spectra of transparent conducting cadmium oxide (CdO) thin films deposited by a modified reactive evaporation process onto glass substrates have been measured. The interference fringes were used to calculate the refractive index, thickness variation, average thickness and absorption coefficient of the films. The influence of the partial pressure of oxygen (PO2), during film deposition on the transmittance, optical constants and bandgap of the films is studied. The observation of an optimum value of PO2 (= 0.040 Pa) at which the transmission is maximum is considered to be a particularly significant result. So, too, is the result that the width of the bandtail has a minimum at the optimum PO2 value. Key words: CdO Films, Optical Transmittance, Evaporation (Global Journal of Pure and Applied Sciences: 2003 9(4): 567-574)
Highlights
The development of cadmium oxide thin films for various optoelectronic devices has stimulated great interest in the preparation and characterisation of the material
The Swanepoel theory is employed to calculate the thickness variation Ad, average thickness d, and the spectral variation of the refractive index t7(A) and absorption coefficient a(h)from the experimental transmission spectra of cadmium oxide (CdO) thin films deposited by a reactive vacuum evaporation process
Such a behaviour had been previously observed for 'InAs thin films where it was founc! that the calculated values of the absorption coefficient a decreased considerably when the effects of the surface roughness were taken into account (Szczyrbowski and Czapla 1977)
Summary
The development of cadmium oxide thin films for various optoelectronic devices has stimulated great interest in the preparation and characterisation of the material. The optical constants (i.e. the real pafi of the complex refractive index, n(h) and the absorption coefficient a@))as well as the thickness d of the films are of utmost importance. The Swanepoel theory is employed to calculate the thickness variation Ad, average thickness d, and the spectral variation of the refractive index t7(A) and absorption coefficient a(h)from the experimental transmission spectra of CdO thin films deposited by a reactive vacuum evaporation process.
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