Zhao Qingxun

Effect of Annealing Temperature on Electrical Properties of Ferroelectric Bi3.25La0.75Ti3O12 Capacitors

Lanthanum-modified bismuth titanate (Bi3.25La0.75Ti3O12, BLT) thin films are fabricated on platinized Si wafers by the sol-gel method, and the effect of annealing temperatures ranging from 650°C to 800°C on the electrical properties of Pt/BLT/Pt capacitors are investigated. It is found that polarization and leakage current of BLT capacitors strongly depend on the annealing temperature although all the capacitors demonstrate very similar characteristics, except the value of polarization, in pulse-width dependence, retention, and fatigue. Remanent polarization increases with the increase of annealing temperature, and annealing temperature of 700°C can yield the largest remanent polarization, and then polarization decreases with increasing annealing temperature. For the 700°C annealed Pt/BLT/Pt capacitor, the remanent polarization 2Pr and the coercive field 2Ec, at an electric field of 226kV/cm, are 23.8μC/cm2 and 130kV/cm, respectively. Dielectric breakdown voltages of BLT films annealed at 750°C and 800°C are much lower than those annealed at 650°C and 700°C. At 100kV/cm, the leakage currents of BLT films prepared at 650°C and 700°C are only 1.5 × 10−6 A/cm2 and 8. 9 × 10−7 A/cm2, respectively. Moreover, all the Pt/BLT/Pt capacitors exhibit excellent retention properties after a cumulative time of 1 × 104 s and do not show any significant fatigue up to 1 × 1010 switching cycles at frequency of 1 MHz.

Morphological study of the localized growth of materials in dielectric barrier discharge

The localized growth of materials has been realized in a dielectric barrier discharge reactor in the mixture of acetylene and argon in previous work. In this paper, the morphology of the materials synthesized in the process is studied. The results indicate that the polymers structure consists of three layers. The layer near the substrate is homogeneous with thickness of several micrometres; the middle layer is composed of dense bulges with height of about more than 10mum in average. The distance between two neighbouring bulges is about 230mum; the top layer is made up of a few large columns with the height up to 2mm, and with the average distance of about 3.5mm. The growth of the three layers corresponds to three types of discharge. The discharge mechanism is analysed through studying the morphology of the polymer. It can be deduced from the morphology that the first and second discharge phases should belong to the Townsend breakdown, and the last discharge phase should be explained on the basis of the streamer mechanism.

Dynamic characteristics of axially symmetric supersonic flow under microwave conditions

Using supersonic dynamics and the Onsager potential transfer differential equation of irreversible process thermodynamics, the dynamic characteristics of the axially symmetric supersonic flow radiated by a microwave beam has been studied theoretically. The results of this research are relatively satisfied in comparison with experimental measurements. It is useful to study parameters of the plasma by ultrasonic methods for plasma diagnostic applications.

Electron spin resonance and microwave absorption spectroscopy of polymers

Using microwave absorption spectroscopy and the theory of electrons and phonons, the matrix element of the interaction Hamiltonian taken between the initial state and the final state of a polymer chain system has been established and electron spin resonance spectroscopy for microwave absorption are discussed from point group theory. In constant frequency intensity calculations, our result, for polyisobutene, is in agreement with experimental measurement.

Dynamic characteristics of conical supersonic flow under microwave conditions

By means of Onsager potential differential equations of irreversible process thermodynamics, dynamic behaviors of a cone (such as a probe) in supersonic flow radiated by microwaves has been researched mathematically. Experience has shown that sufficient accuracy is obtained if the sector between the cone contour and shock front contains subdivisions at intervals of not more than one degree. The result is useful to research parameters of the plasma by an ultrasonic method for plasma diagnostics.

Monte Carlo Simulation of Electron Swarm in the Diamond Film Growth via EACVD

Monte Carlo simulations are adopted to study the electron transport process in the non-uniform electric field. Some important parameters of electrons in diamond films dynamic process at low temperature via EACVD such as angle distribution, energy distribution, average energy of electrons are given. The results indicate that the electron scattering near the substrate is mainly of a large-angle scattering, exhibiting a double-peaking distribution. All of the conclusions provide some theoretical data referential to the vapor dynamic model of diamond film growth at low temperature via EACVD.

The Effect of Pressure on the Dissociation of H2/CH4 Gas Mixture During Diamond Films Growth Via Chemical Vapor Deposition

Monte Carlo simulations are adopted to study the electron motion in the mixture of H2 and CH4 during diamond synthesis via Glow Plasma-assisted Chemical Vapor Deposition (GPCVD). The non-uniform electric field is used and the avalanche of electrons is taken into account in this simulation. The average energy distribution of electrons and the space distribution of effective species such as CH3, CH+3, CH+ and H at various gas pressures are given in this paper, and optimum experimental conditions are inferred from these results.