Chuan-Zhen Ge

LiTaO3 crystal periodically poled by applying an external pulsed field

A method of periodically poling LiTaO3 single crystal at room temperature by applying an external pulsed field is proposed. The relationship between the growth of inverted domains and switching current as well as switching time has been studied. The growth of inverted domains can be controlled by the duration of the pulsed field. The domain structure with period Λ≳8 μm has been fabricated in a 0.3‐mm‐thick plate of LiTaO3 by partial switching.

Preparation of perovskite conductive LaNiO3 films by metalorganic decomposition

Perovskite conductive LaNiO3 films, 250 nm thick, were prepared by metalorganic decomposition. Rutherford backscattering spectrometry was used to determine the film thickness and composition. The x‐ray diffraction patterns of LaNiO3 films indicated that the lowest temperature for crystallization is about 530 °C. The measurement of resistivity as a function of annealing temperatures showed that the good metallic conductive LaNiO3 films could be obtained at 550 °C. The films with the lowest resistivity (4.0×10−4 Ω cm) were obtained on quartz by annealing in oxygen at 700 °C.Perovskite conductive LaNiO3 films, 250 nm thick, were prepared by metalorganic decomposition. Rutherford backscattering spectrometry was used to determine the film thickness and composition. The x‐ray diffraction patterns of LaNiO3 films indicated that the lowest temperature for crystallization is about 530 °C. The measurement of resistivity as a function of annealing temperatures showed that the good metallic conductive LaNiO3 films could be obtained at 550 °C. The films with the lowest resistivity (4.0×10−4 Ω cm) were obtained on quartz by annealing in oxygen at 700 °C.

Fabrication and electrical properties of sol-gel derived BaTiO3 films with metallic LaNiO3 electrode

Metallic LaNiO3 (LNO) films were prepared on LaAlO3 (LAO) by metalorganic decomposition (MOD) and their application as the bottom electrode in sol-gel derived BaTiO3 (BTO) thin film was studied by means of x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. BTO film on LNO-coated LAO exhibited preferred (100) orientation and smooth surface with fine grains (∼50 nm). Electrical measurements on BTO film capacitor showed good ferroelectric hysteresis, lower loss tangent and good insulating properties. These results indicated the BTO/LNO heterostructure fabricated by sol-gel and MOD technique to be a promising combination for microelectronic device applications.Metallic LaNiO3 (LNO) films were prepared on LaAlO3 (LAO) by metalorganic decomposition (MOD) and their application as the bottom electrode in sol-gel derived BaTiO3 (BTO) thin film was studied by means of x-ray diffraction, Raman spectroscopy, and scanning electron microscopy. BTO film on LNO-coated LAO exhibited preferred (100) orientation and smooth surface with fine grains (∼50 nm). Electrical measurements on BTO film capacitor showed good ferroelectric hysteresis, lower loss tangent and good insulating properties. These results indicated the BTO/LNO heterostructure fabricated by sol-gel and MOD technique to be a promising combination for microelectronic device applications.

Second‐harmonic generation of blue light in bulk periodically poled LiTaO3

We fabricated a periodic domain structure in a 0.5 mm thick slab of LiTaO3 crystal by applying an external pulsed field at room temperature. Using a pulse dye laser with a pulsewidth of 8 ns and a repetition rate of 10 Hz, third‐order quasi‐phase‐matched second‐harmonic blue‐light generation is demonstrated by free propagation of a 862.6 nm fundamental Gaussian beam in a 4 mm long LiTaO3 slab, with a single pulse energy of 0.072 mJ and an energy conversion efficiency of 5.7%.

White-beam synchrotron topographic characterization of flux-grown KTiOAsO4

KTiOAsO4 crystals grown from tungstate fluxes have been studied by white‐beam synchrotron radiation topography. It is shown that growth striations are primary planar defects. By anomalous scattering, ferroelectric domains in KTA are investigated and the ratio of ‖F(004)‖2 to ‖F(004)‖2 is calculated. The mechanisms of domain inversion via 2‐fold axis or n‐glide plane are also discussed in terms of the structural characteristics of KTA.

Preparation of epitaxial metallic LaNiO3 films on SrTiO3 by metalorganic decomposition for the oriented growth of PbTiO3

Epitaxial metallic LaNiO3 (LNO) films on SrTiO3 (STO) were prepared by metalorganic decomposition. X‐ray θ–2θ scans, x‐ray φ scans, and the Rutherford backscattering channeling technique were used to determine the degree of crystallinity of the films. The trend of resistance as a function of annealing temperature of LNO films on STO and Si substrates indicated that LNO films on STO have lower crystalline temperature and higher transition temperature from conductor to insulator than on Si. (001)‐oriented PbTiO3 (PT) films were grown on LNO‐coated STO by the sol‐gel method. Scanning electron microscopy of a cross section of PT/LNO/STO showed sharp boundaries. The ferroelectric capacitor fabricated from these films displayed promising P‐E hysteresis characteristics.

Conductive metallic LaNiO3 films from metallo-organic precursors

Abstract Conductive metallic LaNiO3 (LNO) films were prepared by metallo-organic decomposition. 2-Ethylhexanoates of lanthanum and nickel were synthesized as the metallo-organic precursors. The films were obtained by spin-on pyrolysis in air on various substrates and then annealing at various temperature in oxygen or air. Thermogravimetric analysis, inductively coupled plasma analysis, X-ray diffraction, transmission electron microscopy, Rutherford backscattering spectrometry and electrical measurements were used to determine the synthesis process and the characterization of the films. The effect of different thermal treatments, annealing temperature and substrates on crystallinity, orientation and conductive behavior of LNO films was studied. The results indicated the pyrolysis process is the critical step to obtain good metallic LNO films at lower grown temperature. Epitaxial metallic LNO films could be fabricated on SrTiO3 (STO). The trend of resistance as a function of annealing temperature of LNO films on STO, fused quartz and Si substrates showed LNO films on STO have lower crystalline temperature and higher transition temperature from conductor to insulator than on fused quartz and Si.

TEM and AFM study of perovskite conductive LaNiO3 films prepared by metalorganic decomposition

Perovskite conductive LaNiO3 (LNO) films were prepared by metalorganic decomposition. The films were obtained by spin-on pyrolysis on NaCl and SrTiO3(STO) substrates and then annealing at various temperature. The effect of different thermal treatments and annealing temperature on crystallinity, orientation and surface morphology of LNO films was studied. The results obtained by transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray photoelectron spectrometry (XPS) indicated that in the thermal treatment process the oxygen diffusion into the film is the critical step in the fabrication of good metallic LNO films at lower growth temperature. Epitaxial LNO films could be fabricated on STO. The surface morphology of LNO film on STO including the film roughness was recorded by atomic force microscopy (AFM). q 1998 Elsevier Science S.A. All rights reserved.

Structural and electrical properties of PbTiO3 thin films on conductive oxide LaNiO3 coated Si substrates prepared by sol–gel method

Abstract Conductive LaNiO 3 (LNO) thin films were grown on Si substrates by metalorganic decomposition (MOD) and their application as the bottom electrodes for the growth of sol–gel derived PbTiO 3 (PT) thin films. The structure, morphology and electrical properties of the multilayer films were characterized by some analytical techniques and electrical measurements. PT film on LNO/Si had pure perovskite phase with sharp cross-section and small surface roughness. Most Raman modes of PT films shifted to the low frequency due to the pressure effect in the films. PT capacitor showed saturated hysteresis loop, higher resistivity and breakdown voltage. These results indicated the PT/LNO/Si heterostructure fabricated by sol–gel and MOD techniques to be a promising combination for microelectronic device.

Study on the formation mechanism of a complex domain structure in LiNbO3

A complex domain structure in LiNbO3 is fabricated by proton exchange followed by heat treatment. Domain inversion at the +c and −c faces as well as reinversion in the inverted region near the +c surface are observed experimentally. The proton and lithium concentrations are measured by secondary ion mass spectroscopy. It is found that the proton profile peaks away from the surface due to indiffusion and outdiffusion. The domain inversion mechanism is discussed. An internal electric field model is proposed which is based on the concentration gradient of proton and lithium deficiency.