A Study of the LiNbO3 and LiTaO3 Absorption Edge (original) (raw)
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Growth and Study of OH Absorption Band in Doped LiNbO3 Crystals
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Undoped, Mg doped and Mg, Nd codoped LiNbO 3 crystals were grown by conventional Czochralski technique. Comparative study was carried out using Fourier transform infrared (FTIR) spectroscopy. Infrared optical absorption for OH-ion has been used to study the ...
Anomalous temperature dependence of the OH− absorption band in stoichiometric LiNbO3 crystals
Vibrational Spectroscopy
Infrared absorption spectra of the stretching vibration of OH− and OD− ions in stoichiometric LiNbO3 crystal have been measured in the temperature range 10–310 K. The band parameters, halfwidth and position, have been determined with high accuracy by assuming quasi-Voigt line shapes. Anomalous behaviour of the OH− band position has been observed and interpreted by phonons coupled to the stretching vibration with coupling constants of alternate signs.
Stoichiometry dependence of the OH-absorption band in LiNbO 3 crystals
Hydrogen in the form of OH-ions can be incorporated into LiNbO3 single crystals during the growth process. The infrared absorption band due to the OH-defects has been measured at room temperature and a considerable change of the band shape has been observed depending on the crystal composition. The structure of the band found in nearly stoichiometric crystals indicates three slightly different proton sites which can be explained on the basis of the LiNbO3 crystal structure.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1998
The results of ESR measurements on LiNbO 3 single crystal doped with Fe 3 + , Cr 3 + , Mn 2 + or Cu 2 + and also LiTaO 3 doped with Cu 2 + ions are presented. The absorption spectra of these crystals before and after k and electron irradiation are described. The IR absorption band of the OH − group is analysed to determine the most probable location of Cu 2 + and Fe 3 + ions in the LiNbO 3 lattice.
Influence of doping on OH absorption in LiNbO3 crystals
Crystal Research and Technology, 2007
Undoped, Cr doped and Mg, Cr codoped LiNbO 3 crystals were grown by conventional Czochralski technique. Comparative study was carried out using Fourier transform infrared (FTIR) and UV-Visible spectroscopy. Infrared optical absorption for OH⎯ ion has been used to study the effect of dopants on the crystals. The peak position of OH⎯ shift to 3535 cm-1 for Mg, Cr codoped crystals compared to 3484 cm-1 for undoped and Cr doped crystals. Prominent absorption bands are found in the visible region centered at 480 nm (20833 cm-1) and 653 nm (15313 cm-1) in Cr doped crystals. Whereas in Mg, Cr codoped crystals these broad absorption bands are red shifted to 517 nm (19342 cm-1) and 678 nm (14749 cm-1). UV cutoff in Cr doped crystals shift towards higher wavelength compared to undoped LiNbO 3 crystals.
Phonon Anomalies in Optical Spectra of LiNbO3 Single Crystals
Journal of the Serbian Chemical Society
LiNbO 3 single crystals were grown by the Czochralski technique in an air atmosphere. The critical crystal diameter D c = 1.5 cm and the critical rate of rotation w c = 35 rpm were calculated by equations from the hydrodynamics of the melt. The domain inversion was carried out at 1430 K using a 3.75 V/cm electric field for 10 min. The obtained crystals were cut, polished and etched to determine the presence of dislocations and single domain structures. The optical properties were studied by infrared and Raman spectroscopy as a function of temperature. With decreasing temperature, an atypical behaviour of the phonon modes could be seen in the ferroelectrics LiNbO 3 . The obtained results are discussed and compared with published data.
LiNbO3 ground- and excited-state properties from first-principles calculations
Physical Review B, 2008
The atomic and electronic structure, zone center phonon frequencies, and optical absorption of LiNbO 3 are calculated from first principles. The structural and vibrational properties predicted from density functional theory are in good agreement with experiment and earlier theoretical work. The electronic band-structure and optical properties are found to be very sensitive to quasiparticle and electron-hole attraction effects, which are included here using the GW approach and by solving the Bethe-Salpeter equation, respectively. We predict the fundamental gap to be more than 1 eV larger than the 3.7 eV frequently cited for ferrolectric LiNbO 3 and calculate optical absorption spectra in good agreement with experiment.
Optical properties of ferroelectric lanthanum lithium niobate
A B S T R A C T Fine structures (ferroelectric domains), ferroelectricity and Second Harmonic Generation results were found and studied as a function of laser linearly and circularly polarization dependent polarized excitations in ferroelectric stoichiometric La 0.05 Li 0.85 NbO 3 nanocrystals ceramic material. Scanning Electron Microscope images are taken as a comparison to Second Harmonic Generation intensity profiles revealed fine structures. By using laser polar measured response we are able to find the angle orientation from 0° to 90° angles of ferroelectric domains with highly good definition contrast obtained in blue/gray colors. It shows ferroelectric hysteresis loops at room temperature with a polarization saturation of (0.247 μC/cm 2), remnant polarization of (0.15 μC/cm 2) and coercitivity field of (1.31 kV/cm). X-ray Diffraction, Atomic Force Microscope, Raman spectroscopy and X-ray Photoelectron Spectroscopy, revealed well formed of ferroelectric ABO 3 perovskite crystal structure, piezo-electric image response indicate ferroelectric pattern domain structure, new vibrations modes on LaO 6 , LiO 6 and NbO 6 octahedral sites and binding energies of electronic structure of La 57 , Nb 41 , O 8 , Li 3 from the surface of the ferroelectric stoichiometric La 0.05 Li 0.85 NbO 3 nanocrystals ceramic material, respectively.
SNOM study of ferroelectric domains in doped LiNbO 3 crystals
Physics Procedia, 2009
This work shows a study of the periodic ferroelectric domains formed in LiNbO3 crystals doped with rare earths by means of scanning near field optical microscopy (SNOM) technique. It has been observed periodic structures associated with ferroelectric domains with an unexpected high value of the optical contrast working under reflectance SNOM mode. From Raman-Nath diffraction patterns, a refractive index modulation of Δn∼10−4 has been calculated. These results were correlated with the ferroelectric periodic domains obtained by the SNOM technique. A light waveguide effects along the ferroelectric domains is suggested to explain the high reflectance contrast observed in SNOM experiments.