Structural and optoelectronic properties of Zn-incorporated CdO films prepared by sol–gel method

• Published in: Journal of alloys and compounds 2012-10, Vol.539, p.26-31
• Main Author: Dakhel, A.A.
• Format: Article
• Language: English
• Subjects: Carrier density; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Crystallites; Exact sciences and technology; Hume–Rothery rules; Ii-vi semiconductors; Inorganic compounds; Interstitials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Physics; Semiconductors; Sol gel process; Sol–gel method; Spin coating; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; TCO; Water, oxides, hydroxides, peroxides; X-rays; Zinc; Zinc-cadmium oxide; Zn-incorporated CdO
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2012.05.117

The bandgap of Zn-incorporated CdO suffers narrowing by about 8% due to a light (0.51%) incorporation. This behaviour was studied according to the unified BGN with BGW model. It was observed that Zn2+ ions with 0.51% incorporation causes increase in electrical conductivity of host CdO film by about 200% and carrier concentration by about 270%, but decrease in the carrier mobility by about 20%, which can be explained by enhancing of carrier scattering due to the Zn2+ ions occupation of structural interstitials and vacancies. [Display omitted] ► Light Zn-doping is mainly controlled by occupation of host CdO interstitials. ► The bandgap of Zn-incorporated CdO suffers narrowing by about 8%. ► Zn-doping increases the conductivity by 200% and carrier concentration by 270%. ► The carrier mobility decreases by 20% with light Zn-doping. Light zinc incorporated CdO thin films with various Zn concentrations have been prepared on glass and silicon substrates using sol–gel spin coating technique. The films were characterised by the X-rays fluorescence (XRF), X-ray diffraction (XRD), optical absorption spectroscopy, and dc-electrical measurements. The %Zn content in the samples was measured with XRF method and the crystalline structure was determined by XRD method. The experimental results indicated that the major mechanism for light doping of Zn2+ ions is controlled by their occupation of interstitial positions and/or structural vacancies. Furthermore, some of incorporated Zn ions accumulate on crystallite boundaries causing increase in the grain size by joining more crystallites together. The bandgap of Zn-incorporated CdO suffers narrowing by about 8% due to a light (0.51%) Zn-incorporation. The electrical behaviours of the Zn-incorporated CdO films show that they are degenerate semiconductors. It was observed that Zn2+ ions with 0.51% incorporation causes increase in electrical conductivity of host CdO film by about 200% and carrier concentration by about 270%, but decrease in the carrier mobility by about 20%. The phenomenological dependence of the bandgap on the carrier concentration was described according to the available models. Finally, the absorption in the NIR spectral region was studied in the framework of classical Drude theory.