A solution growth route to nanocrystalline nickel oxide thin films

A chemical route for preparation of NiO thin films on glass substrates from solution containing nickel(2 +) ions and urea is presented. The deposition process is based on the fact that urea decomposes to CO2 and NH3 by heating at higher temperature. The as-deposited and post-deposition heat-treated materials were characterized by X-ray analysis and FTIR spectroscopy. The results of some optical and electrical measurements made an these films are discussed. X-ray analysis confirmed that as-deposited film is 3Ni(OH)(2). 2H(2)O, while the post-deposition heat-treated one is nickel oxide with an average crystal size of 13 nm. According to the optical investigations, the absorption coefficient of the deposited material increases upon annealing, the absorption of the annealed films gradually decrease with an increase of the wavelength in the 390-820 nm region. The optical band gap for the post-deposition heat-treated films is 3.6 eV. While the as-deposited thin films are dielectric, the post-deposition treated ones are characterized by resistivity of several M Omega s/cm(2) at room temperature. (C) 2000 Elsevier Science B.V. All rights reserved.