Gujin Hu

Controllable synthesis of WO3·nH2O microcrystals with various morphologies by a facile inorganic route and their photocatalytic activities

WO3·nH2O microcrystals with different shapes have been synthesized via a facile inorganic hydrothermal route. By controlling the amount of Na2SO4 in the precursor solution, hexagonal WO3·0.33H2O nanoplates, WO3 nanorods, and octahedron-shaped WO3·0.5H2O crystals have been obtained, highlighting the role of Na2SO4 in the growth of WO3·nH2O crystals. Based on the experimental observations, we have discussed the growth mechanisms of the WO3·nH2O crystals. The adsorption ability and photocatalytic activities of tungsten trioxide hydrates have also been investigated, and the results show that the WO3·0.33H2O nanoplates with large surface areas show the largest adsorption ability, and WO3·0.5H2O octahedral microcrystals with large bare crystal face exhibit the highest photodegradation performance in these samples, rendering their potential application in the treatment of organic pollutants.

Preparation and optical waveguide property of metal alkoxide solution-derived Pb(Zr0.5Ti0.5)O3 thick films

Pb(Zr0.5Ti0.5)O3 films with thickness of about 1.5 and 3.7 μm have been deposited on single-crystal SrTiO3 substrate by a sol-gel process from nonhydrolyzed metal alkoxide precursor. X-ray diffraction shows that the films exhibit a single perovskite phase with (001)-preferred orientation. Atomic force microscopy study indicates that the PZT film possesses a crack-free and smooth surface. The optical waveguide property has been examined by the prism-film coupling experiment. Four and 12 TE modes are observed for 1.5 and 3.7 μm PZT films, respectively.

Evolution of microstructure and related properties of PbZr0.4Ti0.6O3 films on F-doped tin oxide with annealing temperature

PbZr0.4Ti0.6O3 films were fabricated on glass slices coated with a layer of F-doped transparent conductive tin oxide layer by chemical solution deposition. The evolution of microstructures and related properties of the PbZr0.4Ti0.6O3 films with annealing temperature were studied. The films show a perovskite phase and a crack-free surface morphology. The films annealed at >550 °C display a distinguishable layered structure consisting of dense and porous PbZr0.4Ti0.6O3 layers. The sample treated at 650 °C exhibits the largest average remanent polarization of 29.2 μC/cm2 and peak reflectivity of 95% among the films. 650 °C appears to be the best processing condition for the growth of PbZr0.4Ti0.6O3 multilayers with excellent ferroelectric and optical properties on F-doped tin oxide thin films.

Weak antilocalization effect in high-mobility two-dimensional electron gas in an inversion layer on p-type HgCdTe

Magnetoconductance of a gated two-dimensional electron gas (2DEG) in an inversion layer on a p-type HgCdTe film is investigated. At strong magnetic fields, characteristic features such as the quantum Hall effect of a 2DEG with single subband occupation are observed. At weak magnetic fields, the weak antilocalization effect in the ballistic regime is observed. Phase coherence time and zero-field spin-splitting are extracted following Golub’s model [L. E. Golub, Phys. Rev. B 71, 235310 (2005)]. The temperature dependence of the dephasing rate is consistent with the Nyquist mechanism.

Long phase coherence length and anisotropic magnetoresistance in MgZnO thin film

We comprehensively investigate magnetotransport properties of MgZnO thin film grown on ZnO substrate by molecular-beam epitaxy. We measure the weak localization effect and extract the electron phase coherence length by fitting to a three-dimensional weak localization theory and by analyzing the different changing rate of the magnetoresistance, results of which are in good agreement with each other. The phase coherence length ranges from 38.4±1    nm at 50 K to 99.8±3.6 nm at 1.4  K, almost the same as that of ZnO nanoplates and In-doped ZnO nanowires, and its temperature dependence is found to scale as T−3/4. Meanwhile, we study the anisotropic magnetoresistance resulting from the geometric effect as well as the Lorentz force induced path-length effect, which will be enhanced in higher magnetic fields.

Electrical and optical performance of PbZr0.4Ti0.6O3 optical microcavity derived from one single chemical solution

Fabry-Perot optical microcavity, comprising of two quasiperiodic PbZr0.4Ti0.6O3 multilayers and a dense PbZr0.4Ti0.6O3 space layer, has been fabricated on the F-doped transparent conductive tin oxide thin film by using one single precursor. The obtained multilayer system displays excellent dielectric, ferroelectric, and optical properties simultaneously. It has a dielectric constant of 629 and dielectric tunability of ∼60% at 1 MHz, an average remanent polarization of ∼46.9 μC/cm2, and a quality factor of ∼44, rendering its promising applications in dynamic random access memories, microwave tunable devices and integrated optoelectronics, and an alternative matter system for studying cavity quantum electrodynamics.

Evolution of secondary defects in arsenic implanted Si

Behavior of defects in ion-implanted semiconductors is an everlasting topic and becomes even more critical as semiconductor devices continuously shrink and ion implantation technique has been increasingly employed. High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) were employed to investigate the structural evolution of arsenic (As) implanted silicon (Si). Project range (PR) defects and end of range (EOR) dislocations are observed via HRTEM. EDX characterization proves the two types of defects are related to dopant atoms precipitations. The sizes of both PR defects and EOR dislocations enlarge at the expense of small ones with the elevation of annealing temperature. The characterizations of electrochemical capacitance–voltage and EDX conclude that the SiO2/Si interface is playing an indispensable role in the deactivation of dopant atoms during the annealing process. As atoms are detected in the As-implanted Si region near the SiO2/Si interface but not in the silica layer. Nanoparticles composed of Si atoms in the silica layer are observed in the 1150 °C-annealed samples, which proves the migration of oxygen atoms at the SiO2/Si interface.

An abnormal dielectric relaxation phenomenon observed in PbZr0.38Ti0.62O3 multilayers

We report an unusual dielectric relaxation phenomenon associated with dipolar defect complexes Ti3+-(Vo2−)•• observed in the PbZr0.38Ti0.62O3 multilayers. The dielectric loss aroused by the polarization of defect dipoles varies with time under ac electric fields, and its change can be controlled by an applied dc bias. This abnormally dynamic behavior of dielectric loss can be interpreted by the formation and dissociation of dipolar defect pairs Ti3+-(Vo2−)•• by injection of charged carriers. These investigations may be beneficial to getting further insight into the defect dynamics and the mechanism of ferroelectric polarization fatigue and restoration in ferroelectric materials.