S.X. Shang

Preparation and characterization of Bi2Ti2O7 thin films by chemical solution deposition technique

Abstract Transparent and crack-free Bi 2 Ti 2 O 7 thin films with strong (111) orientation were successfully prepared on n-Si(100) by chemical solution deposition (CSD) using bismuth nitrate and titanium butoxide as starting materials. The structural properties were studied by X-ray diffraction. The dielectric constant at 100 kHz at room temperature was 118 and loss factor was 0.074, for a 0.4-μm-thick film annealed at 500°C for 30 min. The leakage current density was 4.06×10 −7 A/cm 2 at an applied voltage of 15 V.

Sillenites materials as novel photocatalysts for methyl orange decomposition

Abstract Sillenite compounds with a general formula Bi12MO20−x (M=Pb, Ni, Al, Ti, Fe) based on sillenite Bi12O20Si type are effective for the methyl orange decomposition and display higher activity than the TiO2 catalysts.

Preparation and characterization of Bi2Ti2O7 thin films grown by metalorganic chemical vapor deposition

Smooth thin films of Bi2Ti2O7 have been prepared on silicon and fused quartz substrates by metalorganic chemical vapor deposition (MOCVD) at atmosphere pressure for the first time. X-ray diffraction analysis (XRD) showed that films deposited on silicon substrate are single-phase randomly oriented Bi2Ti2O7, and on SiO2 substrates, a (111) orientation was obtained. The films are transparent in visible and near infrared and exhibit a sharp absoption edge at 3nm in the ultraviolet. Measurement of electrical properties gives a dielectric constant (ϵ) of 64, and a loss tangent (tan δ) of 0.01 at room temperature.

Preparation and ferroelectric properties of BaTiO3 thin films by atmospheric-pressure metalorganic chemical vapor deposition

Abstract Ferroelectric BaTiO 3 thin films have been prepared at atmospheric pressure on Si substrate by Metalorganic Chemical Vapor Deposition (MOCVD). Ba(DPM) 2 and titanium isopoproxide (TIP) were used as metalorganic source. The microstructure and composition of the thin films were studied by XRD, SEM and EPMA, respectively. The prepared films at a substrate temperature of 700°C on Si substrate showed polycrystalline structure with smooth and uniform surface. The films have fully textured with (001)-orientation after rapid thermal annealing, and have a dielectric constant ( e ) of 107 and the dissipation factor (tan δ ) of 0.08. The films exhibited remanent polarization ( P r ) of 2.0 μ C cm −2 , and coercive field ( E c ) of 4.0 kV cm −1 , from the P-E hysteresis loop observation. The influence of substrate and stress to the physical properties of the films was mainly discussed. A dispersive Curie peak and the low-temperature-shifted Curie temperature were obtained from the e – T curve, due to the existence of tensile stress on the films.

Preparation and characterization of epitaxial MgO thin film by atmospheric-pressure metalorganic chemical vapor deposition

Abstract Magnesium oxide (MgO) thin films have been prepared on Si(100), SiO 2 (100) Si and Pt (111) Si substrates by atmospheric-pressure metalorganic chemical vapor deposition (AP-MOCVD) for the first time. The relationship between the temperature of substrates (Ts) and crystallographic orientations was also investigated. Magnesium acetylacetonate [Mg(CH2COCH2COCH3)2] was used as the metalorganic source. The relatively low temperature of substrates is about 480°C and the MgO thin films obtained were uniform, dense and well-ordered single crystal. X-ray diffraction experiments provided evidence that the MgO thin films on Si(100) (Ts ≈ 400–680°C), SiO 2 Si and Pt Si were fully textured with (100) orientation. The deliquescent character of MgO thin films was also studied.

Preparation and characterization of MgTiO3 thin films by atmospheric pressure metalorganic chemical vapor deposition

Abstract We report here for the first time, preparation of the ilmenite titanate MgTiO 3 thin films on Si and SrTiO 3 substrates by atmospheric pressure metalorganic chemical vapor deposition (APMOCVD) technique. Magnesium acetylacetonate [Mg(acac) 2 ] and titanium isopropoxide [TIP] were used as the Mg and Ti precursors, and O 2 was the oxidizing gas. The deposited films were investigated using scanning electron microscopy, X-ray energy dispersion analysis and X-ray diffraction technique. The experimental results showed that the films deposited on silicon substrate were single-phase randomly oriented MgTiO 3 , and on SrTiO 3 substrate, only a (0 1 2) orientation was observed. The MgTiO 3 films, prepared on SrTiO 3 (1 0 0) substrates at a growth temperature of 650°C, were transparent in the visible and exhibited a sharp absorption edge at 380 nm in the ultraviolet. The birefringence of the MgTiO 3 films was also measured at room temperature by the cross-correlation method.

The influence of substrate temperature and annealing on phase formation and crystalline properties of bismuth titanate film by APMOCVD

Bismuth titanate thin films have been grown by the atmospheric pressure metal-organic chemical vapour deposition technique. The influences of substrate temperature and annealing on phase formation and crystalline properties have been studied. (100) oriented Bi4Ti3O12 films have been grown at 550 degrees C, while (001) preferred orientation films were obtained at high temperature (about 800 degrees C) annealing. At a temperature of 650-750 degrees C, a film with Bi4Ti3O12+Bi2Ti2O7 phases was formed. It is shown that the phase formation may depend upon the growth temperature and composition of film. The orientation of films mainly depended upon the lattice match with substrate.

Electrical properties of ferroelectric Bi4Ti3O12 thin films by apmocvd

Abstract Bi4Ti3O12 this films with (001) preferred orientation were prepared on Si (100) substrate by APMOCVD and RTA. The dielectric constant is 138 at room temperature, the Curie temperature is about 680°C. The room temperature resistivities were in the range 1010-1013Ω • cm. At low field the film exhibits Ohmic behavior and at high field the space-charge-limited-current conduction is the dominant charge transport mechanism

Structural and electrical characteristics of thin films of prepared by atmospheric-pressure metal-organic chemical vapour deposition

thin films have been prepared firstly by an atmospheric-pressure metal-organic chemical vapour deposition technique. Smooth and polycrystalline films with uniform composition were deposited onto silicon substrates at a substrate temperature of for 1 h and the fully (001)-textured films were obtained with a rapid thermal annealing process thereafter at a temperature of for 60 s. The prepared films exhibited good structural, dielectric and ferroelectric properties. The measured dielectric constant and dissipation factor at a frequency of 100 kHz were 107 and 0.066, respectively, for a thick film annealed at for 60 s. The frequency dependences of the dielectric constant and the dissipation factor were also investigated. The ferroelectricity of the films was confirmed by recording P-E hysteresis loops with remnant polarization and coercive field values of and , respectively. The Curie temperature of the films was found to be 378 K. The influence of stress on the physical properties of the films was investigated.

Segregation growth of large Bi2Sr2CaCu2Oy 90° (100) bicrystal by the self-flux method

The growth of large Bi2Sr2CaCu2Oy bicrystals up to 8 x 4 x 1 mm3 by a self-flux method is reported for the first time. Bicrystals with single 2212 phase were grown by segregating 2201 phase and extra Sr and Ca in flux during crystal growth. The optical morphology and SEM indicated that the as-grown bicrystals have symmetrical 90° (i.e., a-b)(110) twin boundary. A characteristic layer growth morphology suggests that the twin formation occurred layer by layer during crystal growth.