| This paper reports on fabrication of the highly oriented ferroelectric SBN60 thin films by the Sol-Gel and PLD methods. The structure of the films was characterized and the principle of growth was discussed.The SBN60 solutions were prepared by using NbCl5, KOH and Nb(OC2H5)5 as the starting materials respectively. Highly C-axis oriented SBN thin films were obtained on Si(100) and MgO(001) substrates at the post-annealing temperature of 1000 ℃. The microstructures, physical, optical and electro-optic properties of the SBN60 films were characterized by using X-ray diffractometer (XRD), Atomic Force Microscope (AFM), Second Ion Mass Spectroscopy (SIMS), Raman scattering, impedance analyzer, ferroelectric tester, spectrophotometer and electrical induced birefringence set-up. The growth parameters, which can affect the structures and properties of SBN60 films, such as the choice of precursor solutions and post-annealing temperature were discussed.This paper indicates the post-annealing temperature is the key factor which can result in the highly C-axis orientation of SBN60 films on Silicon substrate. The existence of the potassium ions in the precursor solutions make the realization of orientated films became feasible, and the high fost-annealed temperature makes it become reality. It is demonstrated that the high post-annealed temperature results in the severe inter-diffusion of K, Sr, Ba, Nb, Si ions in the interface, and the diffusion lead to the existent of amorphous layer between the top SBN films and bottom Silicon substrate. The existence of the amorphous can solve the strain problem cause by the large lattice mismatch between the SBN film and the silicon substrate, as well as the growth problem caused by the energy difference. This amorphous layer can serve as the buffer layer of the subsequent growth of the top SBN60 films and result in the high orientation of it.According to the indication mentioned above, the sandwich structure of SBN60 / KSBN60 / Si was designed. In order to produce the amorphous layer, the middle KSBN60 layer was post-annealed at 1000℃. Then the top pure SBN60 films were fabricated with the post-annealing temperature from 600 ℃ to 1000℃. It indicates SBN phase can form even at 600 ℃ processing temperature. When the processing temperature increased, the structure and surface quality become better. When the post-annealed temperature is 900 ℃, the film possesses the best crystalline quality and C-axis orientation. So 900℃ is the optimal processing temperature.The SBN60 films were also be fabricated by the Pulsed Laser Deposition (PLD) method. The affection of the potassium ions, the temperature of the substrate and theoxygen pressure to the growth of SBN films on silicon substrate were discussed. It is found the existence of potassium ions the first important factor for the growth of highly C-axis orientated SBN films. And when the substrate temperature is above 720 ℃ and the oxygen pressure is 100mTorr, the films exhibit the best orientation.The measurement of the physical properties, such as Capacity-Frequency, Capacity-Voltage and Polarization-Electric field were also demonstrated for the SBN60 films which fabricated by Sol-Gel method. It indicates the existence of potassium ions result in the lost of part of the ferro-electricity of SBN films, it maybe due to the exhibition of potassium ions which concentrate in the films. Anyway, the potassium ions can also lead to the formation of highly C-axis orientated films.The SBN60 films which deposited on MgO substrate were also studied. The introduction of potassium ions can result in the poor orientation of SBN60 films, but it also changes part of its optical properties. The refractive index of the SBN60 films which contain different amount of potassium ions were modulated by using the Forouhi-Bloomer model. It is found the refractive index exhibits great relationship with the content of potassium ions, which is agree with the results got through prism coupler. The pure SBN60 film possesses the largest value of refractive index which is cl... |
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