Electro-deposition of luminescent molybdate and tungstate thin films via a cell route

Highly crystallized luminescent AMO(4) (A = Ca, Sr, and Ba; M = W, Mo) thin films have been prepared by cell electrochemical technique. Researches reveal that the deposition rate can be tailored by adjusting temperatures and pH values. The optimum temperature is between 308 and 333 K, and the pH value is between 12 and 13.5. X-ray diffraction and photoelectron spectra examinations confirm that the obtained films are polycrystalline AMO(4) (A = Ca, Sr, and Ba: M = W, Mo). Under cell conditions, the homogeneity of films has been improved markedly due to the disappearance of large crystal clusters. At room temperature, a broad emission band ranging from the violet to visible can be observed with the excitation wavelength at 201 nm. Further analyses show that such a broad band can be divided into two sub-bands. Their centers are situated at 357 and 456 nm, respectively. It is proposed that the longer wavelength emission probably originates from MoO42- complex. (C) 2009 Elsevier B.V. All rights reserved.