Papers by Keyword: LiNbO₃

Abstract: The nanocrystalline structure of Lithium niobate (LiNbO₃) was prepared and deposited onto substrate made of quartz by utilize pulse laser deposition technique. The effect of substrate temperature on the structural, optical and morphological properties of lithium niobate photonic film grown was studied. The chemical mixture was prepared by mixing the raw material (Li₂CO₃, Nb₂O₅) with Ethanol liquid without any further purification, at time of stirrer 3hrs but without heating, then annealing process the formed material at 1000C° for 4hrs. We characterized and analyzed the LiNbO₃ nanostructure thin films by utilize Ultra-Violet Visible (UV-vis). The UV-vis measurements show that, when the substrate temperature increases, the values of transmission, absorption and energy band gap will decreased, but the values of reflection and refractive index will increased. That means the LiNbO₃ thin film prepared at substrate temperatures 300C° give the best result for manufacture the optical waveguide.

Abstract: (001)-oriented LiNbO₃ (LN) ferroelectric films were grown on (100)-oriented n-type Si substrates using 15 nm-thick ZnO layers as buffers by pulse laser deposition technique and the LN/ZnO/n-Si heterojunctions were fabricated. Obvious photoswitching characteristics to white light were observed when the reverse voltages were applied on the LN/ZnO/n-Si heterojunction. High performance was exhibited, such as a large ON/OFF ratio, short photoresponse time, steady ON or OFF states, and well reversible. The results were discussed in terms of the band diagrams of the LN/ZnO/Si heterojunctions in this work.

Abstract: The paper is to discuss the main characteristics of the influence of high temperature annealing in different gas environments on the optical and structural properties of congruent lithium niobate crystals.

Abstract: The temperature dependence of the dark electrical conductivity of the LiNbO₃ (LN) crystals annealed in saturated H₂O and D₂O vapor in the range 293...400 K is investigated. It is found that the activation energy of the electrical conductivity is equal to (0.71 ± 0.02) eV and is close this value of LN samples, reduced in hydrogen. Annealing in ampoules with H₂O vapor also lead to LN optical spectra changes such annealing in H₂. The nature of this phenomenon is discussed.

Abstract: Channel waveguides have been fabricated in x-cut lithium niobate (LiNbO₃) by proton exchange (PE) method and optically measured. The thickness and the optical constants of the thin PE layer were characterized using a prism coupling technique. The PE area was plasma etched and a 2.775-μm total etching depth was achieved. The measured average etching rate is 92.5 nm/min. One-and two-dimensional dense arrays of LiNbO₃ nanostructures have also been fabricated by using interference lithography (IL) and inductively coupled plasma reactive ion etching (ICP-RIE) techniques.Intorduction

Abstract: Single crystal of LiNbO₃ has been successfully grown by the Czochralski method in an air atmosphere with a r.f heating crystal growth system namely Automatic Diameter Control Crystal Growth System (ADC-CGS). This paper reports on the effect of new thermal insulation on the growth process of LiNbO₃ single crystal. The effect of hot zone thermal insulation design was investigated. The conditions required to grow high quality LiNbO₃ single crystals are described. A set of crystal growth processes were conducted with the rotation rate of the seed at 15 rpm and the pulling rate at 2.0 mm/hr kept constant. All of the runs were grown along <104> orientation. To control the diameter of the crystal, we have to alter the thermal environment inside the hot zone. In other words, during the crystal growth we have to increase the control power to get smaller diameter and decrease the control power to get larger diameter.

Abstract: The low-frequency impedance spectroscopy method has been used to investigate the electrical conductivity peculiarities of lithium niobate (LN) crystals reduced in hydrogen. It has been found that the activation energy value of the dark electrical conductivity of such crystals in a temperature range of 288...370 К is equal to 0.68±0.02 eV. It has been demonstrated that the multiple heating of «black» LN crystals up to a temperature of about 420 K results in surface layers with modified electrical properties to occur in the crystal’s polar faces. The electrical conductivity mechanism of LiNbO3 crystals reduced in the hydrogen-containing atmosphere, and the causes of the instability of these properties are discussed.

Abstract: The optical waveguides are produced in LiNbO3 substrate of three-component acceleration seismic geophone by lithography. Three-component acceleration seismic geophone detects changes in the external acceleration by detecting phase changes in the optical waveguides. The performance of optical waveguide directly affects the performance of three-component acceleration seismic geophone. Therefore, it is critical to measure and reduce the transmission loss of waveguides. The advantages and disadvantages of LiNbO3 crystal are introduced. The production process of Ti:LiNbO3 optical waveguide and its performance are presented. Some information about the types of transmission loss of optical waveguide and the measurement methods of optical waveguide loss are provided.

Abstract: X-ray radiation using pyroelectric crystal is intermittent and the X-ray intensity is low and unstable compared with a conventional X-ray radiation method, such as X-ray tube. It is expected that the X-ray intensity becomes stable if electric field intensity and supply of electron are stable. In this study, to use X-ray radiation equipment as an electron source, tandem-type X-ray radiation equipment which is composed of two LiNbO3 single crystals polarized in a z-axis is proposed. When the temperature gradient for each crystal was the same, the X-ray intensity became approximately 6 times higher at a maximum. When the temperature gradient for each crystal was reversed, the period of X-ray radiation became approximately two times longer and the X-ray intensity became approximately 20 times higher at a maximum. Moreover, the stability of X-ray radiation for the repetition of temperature could be improved.

Abstract: The gas pressure and the types of ambient gas dependence of X-ray intensity were investigated for LiNbO3 single crystals polarized in the c-axis direction at pressures of approximately 1 to 30 Pa. The integrated X-ray intensity showed a local maximum value at the pressure Pmax. Pmax moved to the high-pressure side in the ambient with a large first ionization energy. Pmax was proportional to the Boltzmann factor using the first ionization energy of each ambient gas molecule. The X-ray intensity was approximated using the quadratic function, which was convex upward for the pressure. It was found that one of the causes of the decrease in X-ray intensity on the pressure side higher than Pmax was the adsorption of positive ions on the crystal electric surface.