| Strontium barium niobate (SixBa1-xNb2O6, 0. 2< x <0. 8, SBN:100x) possesses the largest diagonal electro-optic coefficient, excellent piezoelectric and pyroelectric properties, photorefractive sensitivity and low half-wave voltage among all electro-optic crystals reported to date. The electrooptic coefficient and the pyroelectric coefficient of SBN75 are 1380xl0-12m/V and 31. 0xl0-2μC/cm2K respectively. And the SBN thin film can avoid plumbum pollution of PZT ferroelectric material. SBN has currently being investigated as a potential material for many microdevice applications such as pyroelectric infrared detectors, electrooptic modulators, DRAM, etc. With the rapid development of the optical communication industry, especially the development of integrated optical devices, a successful hetero-epitaxial growth of the film on Si substrate is necessary which can reduce loss in the waveguide effectively.In this paper, the Sol-Gel growth technique, the growth mechnism of SBN thin films and the up-to-date progresses in the research of SBN were reviewed. At the heat-treatment of 1000癈, Highly C-axis oriented SBN thin films were synthesized on Si substrate using the precursors of NbCl5 and Nb(OC2H5)5 respectively. The microstructures and physics properties of the SBN films were characterized by XRD, AFM, SIMS, Raman scattering, and spectrophotometer, electrical induced birefringence etc. The effects of growth parameters on the quality of SBN films were discussed, such as substrates, annealing temperature, and precursor solution, bufferlayer (KSBN, MgO). And then the method to reduce the optics loss was discussed too in this paper.The research indicated that the crystallized phase and degree of orientation were dependent on annealing temperature. Only at higher temperature the TTB SBN can be formed by the reaction of SN and BN phases. It is proved that the approximate single crystal hetero-epitaxial SBN thin film was not formed until heat-treated at 1000癈 on Si substrate. And, the SBN films were found more and more (001) preferential orientated with the increasement of film thickness and it was attributed to the lower layer acting as the buffer one to improve the lattice mismatch between the SBN film and the substrate.Since the lattice mismatch between the MgO substrates and SBN thin films is smaller than that between the silicon substrates and SBN films, at the same heat-treatment temperature, the C-axis preferred orientation of the Nb(OC2H5)5precursor SBN film on MgO substrate is better than on Si substrate. However, the NbCl5-precursor SBN thin films exhibits the same high preferred orientation on Si substrate and the smallest full width at half-maximum(FWHM) value is only 2.5?which is the best result for SBN thin film deposited on Si substrate by the sol-gel method. It was investigated by x-ray diffraction and second ion mass spectrum that the NbCl5-precursorSBN thin films contained Potassium ion. K+ is remnant because of uncompleted filtering of KC1 from the precursor solution, and the molar ratio of k+ to Nb+ was found to be 3:5. K ion dissolving in SBN cell and entering Si substrate can make SBN cell and Si cell a small twist simultaneously, which improves the matching of film and the substrate to hasten the high c-axis superior growth.In addition, the Nb(OC2Hs)5-precursor SBN thin films doping the K+ were crystallized with preferred c-axis orientation which is similar with the orientation of the NbCl5-precursor SBN films. By choosing appropriate contents of K+ there exists the optimum preferred orientation of SBN thin film. And then, The SBN60 thin films deposited onto the K-substituted SBN60 template layers were fabricated. All the films were found exhibiting strong (001) and (002) plane reflection of XRD analysis, and the film with the K+/Nb5+ molar ration of 2/3 (K2/3SBN60 afterwards) showed the strongest intensity of (001) plane reflection. The film surface was uniform and smooth. The Ra value is 4nm. This implies K:SBN buffered SBN thin films fabricated with the sol-gel process have a... |
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