The growth mechanism of nickel oxide thin films by room-temperature chemical bath deposition

Chemical bath deposition (CBD) is an advantageous thin film deposition technique for depositing compound semiconductors at low temperature. In this paper, nickel oxide thin films were prepared by CBD from an aqueous solution composed of nickel sulfate, potassium persulfate, and ammonia at room temperature. Thin film growth mechanisms were studied by using quartz crystal microbalance, UV-vis absorption, and photon correlation spectroscopy. The data indicate that film growth is strongly dependent upon mixing conditions and competes with homogeneous particle formation. No film formation was observed without the addition of persulfate. A growth mechanism based on the combination of particle sticking and molecule level heterogeneous growth is proposed. The as-deposited film contained alpha-Ni(OH)(2) and 4Ni(OH)(2)center dot NiOOH center dot xH(2)O and was converted to nickel oxide (NiO) by thermal annealing according to thermogravimetric, X-ray diffraction and X-ray photoelectron spectroscopy measurements. (C) 2006 The Electrochemical Society.