Potassium-doped strontium barium niobate (SBN) thin films have been fabricated directly on p-type (100)Si substrates using pulsed laser deposition method. The presence of potassium ions and the use of appropriate oxygen pressure help to produce e-axis oriented SBN films. Postannealing at high temperature also enhances the formation of tetragonal tungsten-bronze phase SBN. Excellent guided mode propagation for 632 nm wavelength radiation has been demonstrated. On the basis of our studies, we have shown that highly e-axis oriented SBN films grown directly on (100)Si substrates can be achieved and SBN is a suitable material for developing integrated electro-optic devices. (c) 2006 Elsevier B.V. All rights reserved.

Ferroelectric strontium barium niobate (Sr0.6Ba0.4Nb2O6) thin films have been prepared on p-type Si (100) substrates using sol–gel process. The micro-structure and crystalline phase were studied by X-ray diffractometry, transmission electron microscopy and Raman microprobe spectroscopy. It is found that the SBN films performed a highly c-axis preferred orientation perpendicular to the Si substrates. The preferred orientation is demonstrated to be closely related to the existence of the potassium ions which were not be filtered out completely during the preparation of the niobium alkoxide. High post-annealing temperature results in inter-diffusion of the potassium ions, strontium ions, barium ions and silicon ions, which can create an amorphous layer between the SBN film and the Si substrate. However, the amorphous layer can adjust the large lattice mismatch between the film and substrate and serves as a buffer layer for the highly c-axis orientated SBN films.

We report the growth of highly C-axis orientation of Sr x Ba1−x Nb2O6 (SBN) thin films on p-type (100) Si substrates by using a potassium-substituted SBN template layer with the sol–gel method. The crystallization of SBN thin films was found closely related to the potassium ion doping concentration and the postannealing temperature of the K-SBN template layer. Secondary ion mass spectrometry analysis showed that potassium elements were accumulated at the interface of the template layer and silicon substrate. SBN films postannealed at 750 °C with K-SBN template layer has a smaller full width at half maximum of X-ray rocking curve of 2.45° than that of 5.40° for the pure SBN films. By introducing a template layer, the surface morphologies of SBN films fabricated on silicon substrate were greatly improved.

ZnO were deposited on sapphire and silicon substrates by RF magnetron sputtering from a metallic zinc target. The structural and optical propertied of ZnO films were studied by X-ray diffraction, and UV-VIS-NIR scanning spectrophotometer. XRD measurements show ZnO films had a preferential orientation along the c-axis. Only one peak, (002) phase, appears on the diffraction spectra. The transmittance spectra indicate that ZnO films possessed a transmittance of about 80% in the visible region and a sharp absorption edge at wavelength of about 390nm. The refractive index n and the extinction coefficient k are all sensitive to the oxygen partial pressure and the substrate temperature. Furthermore, based on the ideal five layers symmetrical waveguide films, the relationships of the loss and the thickness of the waveguide layer and the buffer layer were analyzed using ZnO as waveguide layer and SiO2 as buffer layer.

Preferred c-axis oriented Sr0.6Ba0.4Nb2O6 (SBN60) thin films doped with different content of potassium ion have been fabricated by the sol–gel process on MgO(001) substrates. The micro-structure and surface morphology of the films were studied by X-ray diffractometer and atomic force microscopy. It is found that the crystalline properties and the refractive index of the SBN60 films are closely related to the potassium ion concentration in the films. The measured transverse electro-optic coefficient r51 of the SBN60 thin films with K+/Nb5+ molar ratios of 0, 1/7, 1/5, 1/3 and 2/3 are 36.85, 41.72, 43.11, 62.40 and 77.75 pm/V at 633 nm, respectively. An enhancement of r51 with K+ content in the SBN60 films has been clearly demonstrated.

利用溶胶-凝胶法在MgO(001)衬底上获得C轴择优取向的铁电铌酸锶钡(SBN)薄膜,主要介绍MgO(001)衬底上SBN60薄膜及掺入的K离子与Nb离子摩尔比例为1:3的SBN60薄膜横向电光系数r51的测量,实验测得不掺K的SBN60薄膜r51值为37.6 pm/V,掺K的r51值为58.5 pm/V.并由此设计一种基于MgO(001)衬底上的马赫-曾德尔型SBN60薄膜波导调制器,计算出在633 nm时,掺K比例为1:3的此种波导调制器半波调制电压值为10 V,不掺K的半波电压值为16 V,结果说明掺入K离子能增加薄膜的横向电光系数并有效的减少波导的半波调制电压.

BaTiO 3 /polycarbonate (BT/PC) composite thin films were prepared by spin coating method. Ultra-fine BaTiO 3 (BT) (greater than or similar to 40-50 nm) nanocrystals with pure perovskite tetragonal phase were synthesized by hydrothermal method. The structure of BT nanocrystals and composite films were studied by means of x-ray diffraction and transmission electron microscopy. The poling condition was optimized through the dielectric properties of BT and PC polymer and effective field intensity theory. The EO coefficients of 20% wt doped BT nanocrystals composite films were evaluated to 34 pm/v. The orientation degree of nanocrystals in PC polymer was estimated by measuring the transparency spectra of unpoled and poled composite thin films.

Highly oriented ferroelectric strontium barium niobate (Sr(0.6)Ba0.4Nb(2)O(6)) thin films were prepared on P-type Si(100) substrate by the Sol-Gel process. The XRD patterns of the SBN films show that SBN film prepared by using NbCl5, KOH as raw materials performed a highly c-axis preferred orientation perpendicular to the Si substrate, better than films that was prepared using Nb(OC2H5)(5) as starting agents. It may be duo to the existence of the potassium ion that not be filtered out completely during the preparation of the niobium alkoxide. The characteristics of D-F and C-V curves were obtained for SBN/Si film. The film exhibits high dielectric constant. In order to investigate ferroelectric characteristics further, the P-E loops of the SBN/Pt/Si were also measured. The films show better optical properties, transmittance of Sr0.6Ba0.4Nb2O6 films on MgO(001) and SiO2 substrates was more than 60 % at the range from 450 to 850nm, refractive index was measured to be 2.14 and 2.12 on the MgO and SiO2 substrate at 633nm respectively.

High-quality z-axis oriented SBN60 thin films on MgO(001) substrates have been grown by sol-gel process, The transverse electro-optic coefficients r_(51) of the SBN60 and potassium ion doped SBN60 thin films were measured respectively. M-Z type waveguide modulators made of SBN60 thin films were designed. The half-wave modulation voltage was demonstrated to be decreased with the K ion doping.

Strontium barium niobate thin films on Si (001) substrates were obtained by sol-gel method. Highly c-axis oriented films were obtained by using the NbCl5 precursor instead of Nb(OC2H5)5-precursor, appropriate annealing temperature and introduction of buffer layer.

Dense and crack-free SBN thin films with the preferred c-axis orientation were successfully fabricated by the sol-gel method on Si(100) substrates with a MgO buffer layer. It was found that introducing the MgO buffer layer could effectively promote the formation of TTB SBN phase from SN and BN phases at lower temperature. Effects of annealing temperature and thickness of MgO buffer layer on the structural and morphological properties of SBN thin films were investigated. The SBN film with MgO buffer layer showed excellent epitaxy and densely packed grain morphology. The capacitance-voltage (C-V) properties of SBN films deposited on silicon substrates were found completely different from those of the films deposited on MgO-buffered silicon substrates, the C-V curves of SBN/Si films and SBN/MgO/Si films represent typical shapes of asymmetric and butterfly, respectively, indicating the improvement of the electrical properties and ferroelectric properties of the SBN films by introducing the MgO buffer layer.

In order to obtain preferred c-axis orientation and optical properties zinc oxide. ZnO thin films were deposited on sapphire, silicon and glass substrates by RF magnetron sputtering from a metallic zinc target. The sputtering gas was obtained from an oxygen-argon mixture, at 0.7Pa pressure and an O-2-to-Ar ratio of 1:2. The structural and optical propertied. of ZnO films were studied by X-ray diffraction, and UV-VIS-NIR scanning spectrophotometer. By using the Forouhi-Bloomer model, the refractive index (n) and extinction coefficient (k) could be calculated. XRD measurements show ZnO films with epitaxial growth had a preferential orientation along the c-axis. Only one peak, corresponding to (002) phase, appears on the diffraction spectra. The crystallite size was found increasing with the treatment temperature. The transmittance spectra indicate that ZnO films possessed a transmittance of about 80% in the visible region and a sharp absorption edge at wavelength of about 390nm. The refractive index, the extinction coefficient and the optical gap E-g are all sensitive to the RF power and post-annealing temperature. The optical band gap will shift from 3.232eV to 3.271 eV by annealing in oxygen atmosphere at 800degreesC. When the wavelength is close to 390nm, the extinction coefficient will increase rapidly.

Using Forouhi-Bloomer model and modified ‘Downhill’ simplex method, optical constants and film thickness of crystalline SBN60 films with different potassium ion doping ratio are obtained by fitting the measured transmission curve.

Abstract： BaTiO3/PC composite thin films were prepared by spin coating method. Ultra-fine BaTiO3 (BT) (~40-50 nm) nanocrystals with pure perovskite tetragonal phase were synthesized by hydrothermal method. The structure of BT nanocrystals and composite films were studied by means of XRD and TEM. The composite films were poled with a high electric field at a suitable temperature to yield a noncentrosymmetric arrangement and get better electro-optic properties. The poling condition under external electric field was optimized through the dielectric properties of BT and PC polymer and effective field intensity theory. The EO coefficients of different concentration of doped BT nanocrystals composite films were also evaluated. The orientation degree of nanocrystals in PC polymer was estimated by measuring the transparency spectra of unpoled and poled composite thin films.