Photoluminescence Properties Of Eu-doped Cawo₄thin Films Grown By RF Magnetron Sputtering

White LED, which is widely applied in our daily life, is replacing the traditional lightingmethods in modern lighting field. The studies showed that Eu3+doped CaWO4is a kind of redphosphor with stable luminescent properties which could be excited not only by UV light(254nm), but also by near-UV (393nm) and blue light (465nm), with its excited wavelengthmatches well with the UV LED or blue LED chips applied in commercial. Compared withpowder phosphors, thin-film phosphor exhibit more excellent properties in resolution, contrastratio, coating uniformity, thermal stability, lack of out-gassing problems and adhesion tosubstrate.CaWO4:Eu3+thin films have been deposited on silicon substrates by the radio frequency(RF) magnetron sputtering technique. The results are listed as follows:1. Ca0.64WO4:Eu0.24ceramics with a relative density of87%has been prepared using thetraditional ceramic technologies. XRD analysis shows that there exist two phases inCa0.64WO4:Eu0.24ceramics when the sintering temperature is above1100℃. The main phaseis the tetragonal CaWO4, and the other is the monoclinic Eu2WO6.2. The intensities of the luminescence of these samples will be influenced greatly by theannealing temperature. It was found that crystallization increased with the increasing ofannealing temperature. The structure of CaWO4:Eu3+films transferred non crystalline tocrystalline with the red emission intensity increasing. CaWO4:Eu3+thin films should beannealed at the temperature in the range from700to800℃; Otherwise, no sharp and strongred emission corresponding to Eu3+-ion could be observed;800℃for3hours is the best forthe annealing processes.3. Orthogonal experiments show that when the doping concentration is low (2%), theintensity of red emission is affected by sputtering pressure, sputtering power and sputteringtime in the order of strength; The intensity of red emission is improved by higher sputteringpressure (1.0Pa). When the doping concentration is higher (24%), the intensity is affected bysputtering time, sputtering power and sputtering pressure in the order of strength. In addition,low sputtering pressure (0.2Pa) is favorable to the intensity of red emission.4. The X-ray photoelectron spectroscopy (XPS) and X-ray diffractometer (XRD) showsthere are Eu, Ca, W and O in the sample surface; All the CaWO4:Eu3+thin films have scheelitestructure, with no other impurity phase.The Phenomenon of energy transfer between CaWO4 substrate and Eu3+ion7D0â†'5Fj(j=0,1,2,3,4) can be observed under the220nm excitation,in which the strongest emission peak is electric dipole transition of5D0â†'7F2(616nm).