[en] Samarium-doped bismuth titanate [Bi_4-xSm_xTi₃O₁₂ (BSmT)] thin films have been grown on n-type Si (100) substrates using metalorganic decomposition and subsequent annealing at 700 deg. C for 1 h. X-ray diffraction analysis showed layered perovskite structures with a single phase in the films. The current-voltage characteristics displayed ohmic conductivity in the lower voltage range and space-charge-limited conductivity in the higher voltage range. The capacitance-voltage characteristics of Au/BSmT/Si (100) exhibited hysteresis loops due to the ferroelectricity and did not show large carrier injections. The fixed charge density and the surface state density of BSmT films on Si substrate were calculated to be in the range of 10¹¹ cm^-2 and 10¹² cm^-2 eV^-1, respectively

[en] Raman-scattering investigations in two crystals, Er:Yb:YCa₄O(BO₃)₃ (EYYCOB) and Er:YCa₄O(BO₃)₃ (EYCOB), show that the Yb³⁺ ions doped in the crystal largely change the crystal Raman spectra especially those of the Raman tensor elements α_XX, α_ZZ, α_XY, and α_YZ, which imply the better nonlinear optical properties possible for this crystal as a nonlinear optical material, and these Yb³⁺ ions due to their influence on the symmetry of some Rare-earth (RE)-O octahedra also change their ligand field, which imply the better laser properties possible for this crystal as a laser material. These Raman measurements also show that the characteristic spectra of the crystals is mainly contributed by the BO₃ triangles and partly by the Ca(1)O₆ octahedra, which imply that the structural rigidity of the crystals is mainly ascribed to the B-O bond stretching and bending and partly by the Ca(1) - O bonds. On the basis of Judd-Ofelt theory, the effect of the sensitizing Yb³⁺ ions on the absorbance is analyse by comparing with the absorption spectra of EYYCOB and EYCOB. The spectral parameters around the pumping wavelength of an InGaAs diode laser and the luminescence parameters at about 1500 nm also are calculated for the crystal EYYCOB. These indicate that the crystal EYYCOB as a nonlinear optical and laser material would be excellent especially the radiation laser around 1500 nm to be desirable

[en] Samarium-substituted bismuth titanate (Bi_3.15Sm_0.85Ti₃O₁₂ (BSmT)) thin films have been grown on n-type Si (100) substrates by metalorganic decomposition and spin-coating technique. X-ray diffraction and scanning electron microscopy (SEM) analyses confirmed that the crystallinity of the films increases with increasing annealing temperature and the optimum temperature was found to be 700 deg. C. The Raman measurement showed an increase in structural distortion due to the changed ionic radius and atomic mass of Sm ions. The current-voltage characteristics displayed good insulating properties for a film annealed at 700 deg. C for 1 h. The capacitance-voltage characteristic hysteresis curves revealed that the ferroelectric property sufficiently controlled the silicon potential. The measurements of the dielectric constant and dissipation factor of BSmT as a function of frequency exhibited excellent dielectric properties

[en] The adsorption and decomposition of 1,3-disilabutane (DSB) was studied on Si (111)-7x7 in the temperature range 100-1200 K by Cs⁺ reactive ion scattering and X-ray photoelectron spectroscopy (XPS). By combining the results of these two techniques, adspecies in the intermediate states during the decomposition of DSB were qualitatively identified and an adsorption model was proposed. At 100-150 K, DSB was found to adsorb on the surface as the C₂H₈Si₂ species as well as CH₄Si and to condense molecularly on a monolayer of C₂H₈Si₂ adspecies. XPS indicates that the molecular species desorbs mostly at 200 K and completely at 300 K. Up to 600 K, the C₂H₈Si₂ adspecies are converted to CH₄Si with increasing temperature and then above this temperature the CH₄Si species decomposes to form the SiC film. The intensity variations of Si (2p) and total C (1s) peaks and the analysis by curve fitting of the C (1s) peaks suggest that one CH₄Si species leaves the system by cleavage of C-Si bonds in C₂H₈Si₂ adspecies rather than to form two CH₄Si adspecies, and the breakage probably occurs within the extremity ones in accordance with the double-bonded chemisorption character

[en] Single crystals of potassium sodium strontium barium niobate (KNSBN) and cobalt-modified KNSBN were prepared using the Czochralski technique. The ferroelectric hysteresis loops and the infrared reflectivity spectra were collected. Compared with the undoped KNSBN crystals, the cobalt-modified crystals have stable hysteresis loops, whose spontaneous polarization is about 0.17C/m² and coercive field strength is about 670 V/mm, but those of the undoped KNSBN crystals are about 0.04C/m² and 530 V/mm, respectively. The measured infrared reflectivities vary with the orientations of the dipole moments owing to the Co doping. The c axis becomes the most stable orientation of the dipole moments, and the polarization can be locked and does not recede when the cobalt-modified crystals are polarized into a single domain. copyright 1997 American Institute of Physics

[en] The birefringence of (Ca_0.28Ba_0.72)_0.75(Sr_0.60Ba_0.40)Nb₂O₆ crystal is measured basing on polarization- extinction method and conoscopic interference method. Experimental results show that the birefringence in this crystal is up to 10^-5, the natural birefringence in this crystal is (n_o-n_e)=5.89 x 10^-5 with the He-Ne laser wavelength at 632.8 nm and the birefringence grads with wavelength at 532 nm is 5.68 x 10^-5, which indicate the good optical homogeneity of this crystal. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] In open-circuit boundary conditions, tetragonal tungsten bronze (CSBN75) crystals are settled on one of arms of Michelson's interferometer in such a way that even minor perturbation of the penetrated beam can be enlarged and observed through the Michelson's interferometer rings. The experimental results shows that CSBN75 (Δn < 0) are self-defocusing photorefractive crystals. In this paper, qualitative and quantitative discussion on the light-induced change in the index of refraction is given. The self-defocusing character in CSBN75 suggests that it is possible to observe the dark spatial solitons with this crystal in further investigation. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] The self-pumped phase conjugation in CSBN75 is studied in this investigation basing on an anti-traditional method, which using part laser spot to irradiate crystal. With the change of the spot size projected on the crystal, the deformed laser spot that introduced by self-pumped phase conjugation and its complementary pattern are distinctly displayed on the screen. Tentative analysis is executed in this paper. However, it will be applied in optical information processing with these crystals. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Conoscopic interference of polarized light for the white-light and LPS-7,5Volts direct current semiconductor laser (Green light) with wavelength at 532 nm in (Ca_0.28Ba_0.72)_x(Sr_0.60Ba_0.40)_1-xNb₂O₆ crystals were observed with the beams transmitting along optical-axes and deflection optical-axes from 0 to 140 . Endo-exo variation from looseness to tightness of conoscopic interference patterns were analyzed in theory. A hyperbolic black cross of interference patterns were observed as well as its formation process was proposed in this paper. Also, the inferences of the birefringence with different Ca²⁺-doped were obtained in this investigation. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

[en] Based on the space group theory, the normal vibration modes of La₃Ga₅SiO₁₄ (LGS) crystal were predicted, and the Raman scattering intensities of non-polar and polar modes were calculated respectively. The lattice vibration and structure of LGS crystal were investigated by Raman spectroscopy and density-functional theory (DFT). The DFT calculations were made on SiO₄, GaO₄, GaO₆, La₃Ga₄O₁₂ and La₃Ga₃SiO₁₂ clusters, which model the atomic cluster in LGS crystal. Excellent agreement has been achieved between vibrational frequencies predicted by the theory and those observed in experiments. The layer structure of LGS crystal is identified, and its excellent piezoelectric properties are mainly attributed to the large polarizability anisotropy of La₃Ga₄O₁₂ and La₃Ga₃SiO₁₂ clusters, which results from the strong interaction between Ga(Si)O₄ tetrahedras of LGS crystal. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)