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

In recent years, due to its applications in photoelectric industry, rare-earth-doped compound semiconductors are drawing more and more attentions. Because of being shielded by electrons in their outer 5s25p6, the impact of fields from host crystal on 4f electrons of rare earth elements are very small and their f-f transition emission exhibit a characteristic sharp luminescence emission. The 5D0-7F2 transition of Eu³⁺can result in the emission of red light with the wavelength of about 610nm, being one of the important luminescent materials in photoelectric devices.ZnO is a kind of II-VI wide direct band gap semiconductor with band gap energy of 3.37eV at room temperature and exciton binding energy as large as 60meV, much higher than thermal ionization energy (26meV), its thermostability and chemical stability are excellent as well. Together with properties such as non-toxicity, easy-etching, low cost and compatibility to silicon integration technology, ZnO is becoming an excellent rare earth doped host material for visible light emitting. ZnO films can intensively absorb the ultraviolet light. After doping with rare earth elements, the absorbed energy can be transferred to rare earth luminescent centers, achieving visible light emitting and being applied in fluorescent converting typed LED, which means using high bright near UV LED excite ZnO:RE³⁺films, resulting in the characteristic visible light emitting of RE³⁺In this thesis, ZnO:Eu³⁺ films were prepared on quartz substrates by RF magnetron sputtering. X-ray diffraction (XRD), scanning electron microscope (SEM) and spectrometer were employed to characterize their structure, surface morphology and luminescent performance. Effects of technological parameters such as sputtering power, the ratio of oxygen and argon, substrate temperature, annealing process and dopant concentration on their properties were studied in detail. The results are listed as follows:1. All of the films have a hexagonal wurtzite structure of ZnO, and there are no impure phase; increasing RF sputtering power and proper oxygen/argon ratio improves the (002) preferred orientation; the grain size increases with increasing RF sputtering power and heat treatment. 2. When using 372nm excite sample, the phenomenon of energy transfer between ZnO substrate and Eu³⁺ ion 5D0-7Fj(j=0,1,2,3) can be observed, with the strongest transition of 5D0-7F2(611nm).3. By using the 5D0-7F2(611nm) transition of Eu³⁺ as monitoring wavelength, the measured PLE consisted of the indirect activation of ZnO and direct activation of Eu³⁺. Among them, the band-to-band activation and free exciton activation were dominant, indicating there were effective energy transferring between ZnO substrate and Eu³⁺ ion.4. Increasing sputtering power(190w) and substrate temperature(580℃), proper dopant concentraton(1.7%) and oxygen/argon ratio(3:17), especially high temperature(700℃) annealing in air can improve the red light emitting of ZnO:Eu³⁺films.