Sun Jinglan

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.

Polarization of Hemicyanine Langmuir–Blodgett Films

The polarization dependence of electric field for hemicyanine layers deposited by the Langmuir–Blodgett (LB) technique has been measured. The experimental results show that ferroelectricity exists not only in thick films (200 nm) but also in thinner films (30 nm), and the remnant polarization is related to film thickness. In order to interpret the measured results, a planar rotor model was introduced, and a relation between polarization and film thickness was obtained by perturbation theory. The theory fitting agrees with experimental results well. It is confirmed that ferroelectricity in organic molecular LB films mainly arose from altering of molecular orientation.

Green/Blue Photoluminescence from Nanocrystalline Si Thin Films by Rapid Thermal Processing

The green/blue photoluminescence with peaks centered around 2.4 eV at room temperature was observed from nanocrystalline Si thin films prepared by the three-step rapid thermal annealing of hydrogenated amorphous silicon films. The effect of the parameters of rapid thermal annealing on the light emission was studied. A comparison of photoluminescence feature between the films from the rapid thermal annealing and the furnace annealing of a-Si:H has been carried out.