Jianli Ma

Uniaxial Stress Induced Electron Mobility Enhancement in Silicon

The conduction band structure of Si under uniaxial [100] stress is investigated by using the two band k·p perturbation theory. The conduction band parameters, including the conduction band minimum energy shift, split and electron effective mass change are quantitative described. Based on these band parameters, uniaxial stress induced electron mobility enhancment is systematically studied through Boltzmann transport theory. The results show that, when uniaxial [100] stress is applied to Si crystal, a gain of more than 50 % in electron mobility can be obtained. The electron mobility along the [100] increase with tensile stress and decrease with compressive stress, while does the opposite for the electron mobility along the [010] and [001]. The electron mobility along the [100], [010] and [001] tend to saturate for stress beyond a certain level. The stress induced the reduction of conductivity effective mass and the suppression of inter-valley scattering rate are responsible for the enhancement of electron mobility. The calculated results provide valuable reference for the optimum stress and orientation of the conduction channel in the uniaxial strained Si nMOS devices design. The electron mobility calculated model used in the present work is suitable for implementation in TCAD simulators.

The effect of sintering agents on the sinterability and dielectric properties of Li2Mg3TiO6 ceramics

ABSTRACT The low-fired Li2Mg3TiO6 ceramics were fabricated via doping several multicomponent sintering agents. The effect of multicomponent sintering agents on the sinterability and microwave dielectric properties of Li2Mg3TiO6 ceramics were investigated. The results showed that the densification temperature of Li2Mg3TiO6 ceramics was reduced to 950°C, 975°C and 1000°C by doping LC, LV and LB as sintering agents, respectively. The optimum dielectric properties of ϵr = 15.7, Q × f = 70100 GHz and τf = −43 ppm/°C were obtained at 950°C for LC-doped Li2Mg3TiO6 ceramics. Such sample was compatible with Ag electrodes, suitable for the low-temperature co-fired ceramics (LTCC) applications.

The Lévy noise-induced current reversal phenomenon for self-propelled particles in a two-dimensional potential

Effects of Levy noise on self-propelled particles in a two-dimensional potential is investigated. The current reversal phenomenon appears in the system. V (x-direction average velocity) changes from negative to positive with increasing asymmetry parameter β, and changes from positive to negative with increasing self-propelled velocity v0. V has a maximum with increasing modulation constant λ.

Effects of preparation methods on synthesis, microstructures and microwave dielectric properties of Li2TiO3 ceramics

ABSTRACT The Li2TiO3 ceramics were fabricated by a conventional solid-state method (CSS) and a high-energy ball-milling method (HEBM), respectively. The effects of prepared method on the synthesis, microstructures and dielectric properties of Li2TiO3 were investigated. By using HEBM method, a pure Li2TiO3 powders were synthesized with grain size of 30–80 nm at 500°C, 200°C lower than that synthesized by using CSS method. Furthermore, Li2TiO3 ceramics were obtained at 1175°C and 1000°C by using CSS and HEBM method, respectively, and displayed similarly microwave dielectric properties: ϵr = 17.5, Q × f = 51000 GHz, τf = 28.2 ppm/°C and ϵr = 16.5, Q × f = 54300 GHz, τf = 27.5 ppm/°C.