GEOMETRIC AND ELECTRONIC STRUCTURES OF Ti8C12 CLUSTER

The electronic structure of Ti₈C₁₂ clusters with three possible geometric structures suggested in the literature is studied using the discrete-variational local-density-functional method. The results show that the ground states of the clusters are all degenerate, which means further Jahn-Teller distortions for the geometric structures of clusters. The results also indicate that the distorted dodecahedral Ti₈C₁₂ cluster, which is proposed by Guo et al. and optimized by the first principle calculations, is the most stable one among the clusters we considered and its electronic structure can explain the experimental observations. In this cluster, there is a strong pd bonding between Ti and C atoms, and the density of states at the Fermi energy is high.     

GEOMETRIC AND ELECTRONIC STRUCTURES OF Ti8C12 CLUSTER

The electronic structure of Ti₈C₁₂ clusters with three possible geometric structures suggested in the literature is studied using the discrete-variational local-density-functional method. The results show that the ground states of the clusters are all degenerate, which means further Jahn-Teller distortions for the geometric structures of clusters. The results also indicate that the distorted dodecahedral Ti₈C₁₂ cluster, which is proposed by Guo et al. and optimized by the first principle calculations, is the most stable one among the clusters we considered and its electronic structure can explain the experimental observations. In this cluster, there is a strong pd bonding between Ti and C atoms, and the density of states at the Fermi energy is high.     

HTML5对数字图书馆的影响

HTML5目前得到了苹果及谷歌公司这两大移动互联网巨头的大力支持而在智能手机和平板电脑上得到了广泛应用。同时,移动设备也已经成为图书馆服务的新载体。本文介绍了HTML5的主要特点,分析了HTML5在移动设备上的优势,讨论了其对数字图书馆发展的影响。【     

土体性质对Cl-迁移过程影响的试验研究

通过室内土柱试验模拟污染物迁移,分析了平均粒径、孔隙比、不均匀系数等土体性质对迁移规律的影响。试验结果表明:平均孔隙流速随着土样平均粒径的增大而增大,初始穿透时间随着土样孔隙比变大而缩短;弥散系数随着平均粒径、孔隙比的增大而增大。通过试验数据拟合得到符合试验土样的弥散系数经验公式。试验结果为污染土体及地下水体的防治工作提供依据。     

A simple and accurate method for measuring program/erase speed in a memory capacitor structure

With the merits of a simple process and a short fabrication period, the capacitor structure provides a convenient way to evaluate memory characteristics of charge trap memory devices. However, the slow minority carrier generation in a capacitor often makes an underestimation of the program/erase speed. In this paper, illumination around a memory capacitor is proposed to enhance the generation of minority carriers so that an accurate measurement of the program/erase speed can be achieved. From the dependence of the inversion capacitance on frequency, a time constant is extracted to quantitatively characterize the formation of the inversion layer. Experimental results show that under a high enough illumination, this time constant is greatly reduced and the measured minority carrier-related program/erase speed is in agreement with the reported value in a transistor structure.     

A simple and accurate method to measure program/erase speed in a memory capacitor structure

With the merits of simple process and short fabrication period, the capacitor structure provides a convenient way to evaluate memory characteristics of charge trap memory devices. However, the slow minority carrier generation in a capacitor often makes an underestimation of the program/erase speed. In this paper, illumination around a memory capacitor is proposed to enhance the generation of minority carriers so that an accurate measurement of the program/erase speed can be achieved. From the dependence of the inversion capacitance on frequency, a time constant is extracted to quantitatively characterize the formation of the inversion layer. Experimental results show that under a high enough illumination, this time constant is greatly reduced and the measured minority carrier related program/erase speed is in agreement with the reported value in a transistor structure.     

Electron trapping properties at HfO_2/SiO_2 interface,studied by Kelvin probe force microscopy and theoretical analysis

Electron trapping properties at the HfO_2/SiO_2 interface have been measured through Kelvin Probe force microscopy,between room temperature and 90 ℃.The electron diffusion in HfO_2 shows a multiple-step process.After injection,electrons diffuse quickly toward the HfO_2/SiO_2 interface and then diffuse laterally near the interface in two sub-steps:The first is a fast diffusion through shallow trap centers and the second is a slow diffusion through deep trap centers.Evolution of contact potential difference profile in the fast lateral diffusion sub-step was simulated by solving a diffusion equation with a term describing the charge loss.In this way,the diffusion coefficient and the average life time at different temperatures were extracted.A value of 0.57 eV was calculated for the activation energy of the shallow trap centers in HfO_2.     

用推广的平面波展开法检验平面内极化的电子子带跃迁

把平面波展开包络函数的方法推广到求解8带的哈密顿量，使它同时包括Γ^c₁和Γ^v₁₅．在这种方法里，可以考虑反演不对称性、能带的非抛物性、有效质量不连续性以及自旋轨道耦合等效应的影响．作为应用，计算了两个量子阱结构的子带和光跃迁概率．实验上在这两个结构中观察到了平面内极化的电子子带跃迁．计算表明这种跃迁的概率很小．实验上观察到的平面内极化的电子子带吸收可能有其他的机制 关键词：     

简述公路工程土石方调配

路基土石方工程是公路工程路基的重要组成部分,是一种工程量大、劳动量多、施工条件复杂多变的工程。结合纬地软件,简述公路路基土石方调配中的相关问题。     

完善我国食品召回制度的法律思考

本文在分析我国食品公告收回制度和不安全食品召回制度存在的问题的基础上，提出了我国完善食品召回制度的相关对策。