Meng Xiangjian

Ferroelectric Properties of BiFeO3 Thin Films Prepared via a Simple Chemical Solution Deposition

Bi1+xFeO3 (BFO, x = 0,0.05,0.1,0.15) thin films are fabricated on LaNiO3 (LNO) buffered Si substrates by using a polymeric precursor solution under appropriate crystallization condition. All films possess highly (100) preference oriented. SEM analyses show that the average grain size decreases and thin films become dense and smoother with increasing of excess Bi content. The enhancement of polarization and improvement of leakage current are observed for BFO thin films with 10% excess Bi content. It indicates that the optimized excess Bi content plays an important role in the microstructure and ferroelectric property for BFO thin films.

Fabrication and characterization of an AlGaN/PZT detector

Design, fabrication and characterization of a novel two-color detector for ultraviolet and infrared applications are reported. The detector has a simple multilayer structure composed of n-Al0.3Ga0.7N/i-GaN/p-GaN/SiO2/LaNiO3/PZT/Pt fabricated on a sapphire substrate. Ultraviolet and infrared properties are measured. For the ultraviolet region, a flat band spectral response is achieved in the 302–363 nm band. The detector displays an unbiased responsivity of 0.064 A/W at 355 nm. The current-voltage curve shows that current at zero bias is −1.57 × 10−12 A. This led to a detectivity of 1.81 × 1011 cm · Hz1/2/W. In the infrared region, the detectivity of the detector is 1.58 × 105 cm · Hz1/2/W at 4 μm.

Structural and electrical properties of SrTiO3 thin films as insulator of metal-ferroelectric-insulator-semiconductor （MFIS） structures

SrTiO3 (STO) thin films were deposited on p-Si(100) substrates at various substrate temperatures from 300°C to 700°C by radio frequency (RF) magnetron sputtering technique. Their structure and electrical properties were investigated. It was found that the transition from amorphous phase to polycrystalline phase occurred at the substrate temperatures 300–400°C. Their crystallinity became better when the substrate temperatures further increased. The dielectric and leakage current measurements were carried out by using the Si/STO/Pt metal–insulator–semiconductor (MIS) structures at room temperature. It was found that the fixed charge density decreased and both the interface trap density and the dielectric constant increased when the substrate temperatures were increased. The leakage current mechanisms for STO MIS structures with STO films prepared at 700°C followed the space charge limited current (SCLC) under the low applied electric field and the Poole–Frenkel emission under the high one. In addition, the resistivity for films prepared at 700°C was higher than 1011Ω.cm under the voltage lower than 10V (corresponding to the electric field of 1.54×103kV.cm−1). It suggested that the STO films prepared at 700°C were suitable for acting as the insulator of metal–ferroelectric–insulator–semiconductor (MFIS) structures.

Optical properties of SrTiO3 thin films prepared by metalorganic decomposition

SrTiO3 thin films were deposited on vitreous silica substrates by metalorganic decomposition (MOD). The films are polycrystalline cubic in structure with the lattice constants of a=0.39nm. Their optical constants (refractive index n and extinction coefficient k) were calculated by the envelope method from the transmittance spectra in the wavelength range of 190nm to 1100rim. The refractive index of the present films is found to be higher than that of the other SrTiO3 films prepared by RF sputtering, sol-gel and chemical vapour deposition. The dispersion of the refractive index in the films follows the single electronic oscillator model with oscillator strength (S0) of 0.88×10^14m^-2 and oscillator energy (E0) of 6.40eV. The optical band gap of the films was estimated to be 3.68eV.SrTiO3 thin films were deposited on vitreous silica substrates by metalorganic decomposition (MOD). The films are polycrystalline cubic in structure with the lattice constants of a=0.39nm. Their optical constants (refractive index n and extinction coefficient k) were calculated by the envelope method from the transmittance spectra in the wavelength range of 190nm to 1100nm. The refractive index of the present films is found to be higher than that of the other SrTiO3 films prepared by RF sputtering, sol–gel and chemical vapour deposition. The dispersion of the refractive index in the films follows the single electronic oscillator model with oscillator strength (S0) of 0.88×1014m−2 and oscillator energy (E0) of 6.40eV. The optical band gap of the films was estimated to be 3.68eV.