The Preparation And Luminescent Properties Of Si/SiO₂/LiNbO₃(:Fe/Mn) Thin Films

LiNbO₃ is often used as SAW and integrated optical devices due to its excellent electro-optical, piezoelectric and nonlinear optical properties. Generally, LiNbO₃ shall be wave-guided structures if it becomes the optical devices. However, there are several problems for depositing wave-guide films through the traditional methods, so fabricating hetero-structure LiNbO₃ films caused an increasing interest. Compared with bulk materials, hetero-structure LiNbO₃ films possess obviously advantages, such as, it can obtain a large refractive index difference between the substrate and wave-guided films. Until now, there exist various techniques to prepare the hetero-structure LiNbO₃ films. Silicon material as the basement of microelectric technology, LiNbO₃ films deposited on it is compatible with semiconductor technology and is easy to optoelectronic integration as well as cheap price. Therefore, it is very meaningful to study the Si-based LiNbO₃ films.In this paper, on the base of introducing the past and current research about LiNbO₃ films, we investigated the preparation and photoluminescent properties of Si/SiO₂/LiNbO₃(:Fe/:Mn) thin films by radio frequency magnetron sputtering. The following results are obtained:1. The photoluminescent properties of SiO₂ buffer layer deposited on Si substrate at room temperature was investigated. The results showed that there were two photoluminescent bands situated at 440nm and 530nm, respectively for the films annealed beyond 800℃in air atmosphere for 1 hour. The former originates from the self-trapped excitons, however, the latter is maybe relation with the oxygen-related defects.2. The influence of experimental parameters on LiNbO₃ films growth and c-axis orientation were investigated. The results showed that the best experimental parameters for LiNbO₃ films with c-axis orientation is 575℃substrate temperature, O₂/Ar flow ratio of 1/2 (total flow is 15sccm), 1.6Pa sputtering pressure, 100W sputtering power, 80mm distance between LiNbO₃ ceramic target and substrate,annealing temperature of 1000℃,annealing time of 0.5h.3. Through using the Li-enriched LiNbO₃ target and optimizing the experimental parameters, we prepared the near-stoichiometric LiNbO₃ films. We presented the growth model: substrate-diffusion layer-amorphous layer-polycrystal layer-c-axis oriental layer. Besides, Fe or Mn doped LiNbO₃ films, it is found that Fe or Mn exists in LiNbO₃ films as Fe³⁺ or Mn³⁺.4. The influence of LiNbO₃ film on photoluminescent properties of Si/SiO₂ film as well as the influence of doped with Fe or Mn on photoluminescent properties of Si/SiO₂/LiNbO₃ multilayer films is investigated. The result showed that at the same excitation wavelength of 340nm, there is a blue emission peak at 470nm. This indicates that the LiNbO₃ film has modulating effects on the photoluminescent properties of Si/SiO₂ films.