Effect of annealing temperature on structural, electrical and optical properties of spray pyrolytic nanocrystalline CdO thin films

• Published in: Materials science in semiconductor processing Vol. 24; pp. 26 - 33
• Main Authors: Azizar Rahman, M., Khan, M.K.R.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.08.2014; Elsevier
• Subjects: Annealing; Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Diffraction; Electrical properties; Exact sciences and technology; Heat treatment; Materials science; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Nanocrystals; Nanostructure; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Production techniques; Scanning electron microscopy; Semiconductors; Spray coating techniques; Structural properties; Surface treatment; Thin films; X-rays; Annealing; Electrical properties; Optical properties; Structural properties; Grain size analysis; Cubic lattices; Spray pyrolysis; Ultraviolet spectroscopy; Nanostructured material; Glass; Annealing temperature; Hall effect; XRD; Nanostructures; Substrat temperature; Thin films; Dislocation density; Temperature effects; n type semiconductor; Optical characteristic; Carrier mobility; Nanocrystal; Electrical characteristic; Grain size; Temperature dependence; Scanning electron microscopy; Voltage measurement; Spray coatings; Carrier density
• DOI: 10.1016/j.mssp.2014.03.002
• ISSN: 1369-8001

Nanocrystalline CdO thin films were prepared onto a glass substrate at substrate temperature of 300°C by a spray pyrolysis technique. Grown films were annealed at 250, 350, 450 and 550°C for 2.5h and studied by the X-ray diffraction, Hall voltage measurement, UV-spectroscopy, and scanning electron microscope. The X-ray diffraction study confirms the cubic structure of as-deposited and annealed films. The grain size increases whereas the dislocation density decreases with increasing annealing temperature. The Hall measurement confirms that CdO is an n-type semiconductor. The carrier density and mobility increase with increasing annealing temperature up to 450°C. The temperature dependent dc resistivity of as-deposited film shows metallic behavior from room temperature to 370K after which it is semiconducting in nature. The metallic behavior completely washed out by annealing the samples at different temperatures. Optical transmittance and band gap energy of the films are found to decrease with increasing annealing temperature and the highest transmittance is found in near infrared region. The refractive index and optical conductivity of the CdO thin films enhanced by annealing. Scanning electron microscopy confirms formation of nano-structured CdO thin films with clear grain boundary.