Quantum Mechanical Study on Tunnelling and Ballistic Transport of Nanometer Si MOSFETs

Using self-consistent calculations of million-atom SchrSdinger-Poisson equations, we investigate the I-V characteristics of tunnelling and ballistic transport of nanometer metal oxide semiconductor field effect transistors （MOSFET） based on a full 3-D quantum mechanical simulation under nonequilibtium condition. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. We find that the ballistic transport dominates the I-V characteristics, whereas the effects of tunnelling cannot be neglected with the maximal value up to 0.8mA/μm when the channel length of MOSFET scales down to 25 nm. The effects of tunnelling transport lower the threshold voltage Vt. The ballistic current based on fully 3-D quantum mechanical simulation is relatively large and has small on-off ratio compared with results derived from the calculation methods of Luo et al.     

Ab initio study of I<Subscript>2</Subscript> and T<Subscript>2</Subscript> stacking faults in C14 Laves phase MgZn<Subscript>2</Subscript>

Based on the synchroshear mechanism, the formation of intrinsic stacking fault I ₂ and twin-like stacking fault T ₂ in C14 Laves phases has been modeled in detail and the generalised stacking fault energy curve of I ₂ and T ₂ for C14 Laves phase MgZn₂ has been calculated from first-principles. The results demonstrate that the unstable stacking fault energy of I ₂ by synchroshear is still very large, and the stable stacking fault energy of I ₂ is higher in comparison with pure Mg implying that the formation of I ₂ stacking fault in MgZn₂ is difficult. Starting with the I ₂ configuration, the T ₂ stacking fault can be formed by an additional synchroshear. The unstable and stable stacking fault energies of T ₂ are only slightly larger than those of I ₂, implying that the formation of T ₂ may be essentially similar to that of I ₂. From the obtained generalised stacking fault energy, the relevant deformation mechanism of MgZn₂ is also discussed. Finally, the electronic structure during synchroshear process is further studied.     

基于双(苯并咪唑)桥联配体构筑的三个配位聚合物的合成、晶体结构及荧光识别性能

利用双(苯并咪唑)桥联配体1,4-双(2-苯并咪唑基)苯(bbib)和4,4′-双(2-苯并咪唑基)联苯(bbibp)与过渡金属盐在水热条件下反应,合成了3种新型的一维配位聚合物,{[Mn(bbib)(H_2O)_4](H_2BTC)·2H_2O}_n(1),[Zn(bbib)Cl_2]_n(2)和[Zn(bbibp)Cl_2]_n(3),并通过元素分析、红外光谱、粉末X射线衍射分析、单晶X射线衍射等对其结构进行了表征。结构分析表明,配合物1中的O-H…O氢键以及配合物2和3中的C-H…Cl氢键在上述配合物的三维超分子结构的构筑过程中起着重要的作用。在考虑配合物强氢键作用的基础上,配合物1的超分子结构可以简化为(4,6)-连接的{42·58·64·7}{42·64}网络,配合物2可以看做是一个5-连接的{43·67}骨架,配合物3可以简化成6-连接(48·67)-msw网络结构。此外,荧光识别性能研究表明配合物2和3可以实现对水相中Fe~(3+)离子的高灵敏性和高选择性识别。     

Electronic Stopping Power for 0.05--10MeV Protons in a Group of Organic Materials

Electronic stopping powers for 0. 05-10 MeV protons in a group of organic materials are systematically calculated. The calculations are based on Ashley＇s dielectric model, and an evaluation approach of optical energy loss function is incorporated into Ashley＇s model because no experimental optical data are available for most of the organic materials under consideration. The Barkas-effect correction and Bloch correction are included. The proton stopping powers for the considered organic materials except for mylar in the energy range from 0.05 to 10 MeV are presented for the first time. The results may be useful for studies of various radiation effects in these materials and for space research.     

Self-Injection and Acceleration of Monoenergetic Electron Beams from Laser Wakefield Accelerators in a Highly Relativistic Regime

Self-injection and acceleration of monoenergetic electron beams from laser wakefield accelerators are first investigated in the highly relativistic regime, using 100 TW class, 27 fs laser pulses. Quasi-monoenergetic multi- bunched beams with energies as high as multi-hundredMeV are observed with simultaneous measurements of side-scattering emissions that indicate the formation of self-channelfing and self-injection of electrons into a plasma wake, referred to as a ＇bubble＇. The three-dimensional particle-in-cell simulations confirmed multiple self-injection of electron bunches into the bubble and their beam acceleration with gradient of 1.5 GeV/cm.     

External Electric Field Effect on Hydrogenic Donor Impurity in Zinc-Blende InGaN Quantum Dot

The binding energy of a hydrogenic donor impurity in zinc-blende (ZB) InGaN quantum dot (QD) is calculated in the framework of effective-mass envelope-function theory using the plane wave basis. It is shown that the donor binding energy is highly dependent on the impurity position, QD size and the external electric field. The symmetry of the electron probability distribution is broken and the maximum of the donor binding energy is shifted from the centre of QD in the presence of the external electric field. The degenerating energy levels for symmetrical positions with respect to the centre of QD are split. The splitting increases with the increase of QD height while the splitting increases up to a maximum value and then decreases with the increase of QD radius.     

Field-induced spin-polarized electronic and optical properties of armchair stanene nanoribbons

Electronic and optical properties of armchair stanene nanoribbons are studied within the $s{p}^3$ tight-binding model including spin-orbit coupling in the presence of in-plane electric field. Electric field strongly modulates energy dispersions leading to a zero-gap transition, shift in edge-states, and exhibition of spin-splitting states. Then, the complex dielectric functions in the long wavelength limit is calculated from the gradient approximation. More field-induced transition channels exhibit richer optical spectra which further reveal spin-polarized feature at low frequency. Prominent plasmons in loss spectra come from π–σ mixing orbital. The plasmon peak frequency and height are tuned by field strength. Also, the threshold plasmon frequency linearly decreases as electric field increases and it vanishes at critical field. The reflectance exhibits oscillatory behaviors and shows dip structures with sharp plasmon edge, undergoing a red-shift with increasing field. The calculated results fully show that field-modulations of electronic and optical properties strongly depend on nanoribbon's geometry.     

甲烷-二氧化碳重整制合成气与现代分析技术应用于探究性化工专业实验的设计与探索

以甲烷-二氧化碳重整制合成气为实例，设计探究性实验，将合成气的制备和现代分析技术应用于化工专业实验的教学实践中以提高学生的创新和实践能力。实验包括催化剂的制备，催化剂的性能评价和催化剂的表征等3大部分。采用工业最常用的浸渍法制备含有不同助剂的Ni/X/γ-Al2O3（X为Co，Fe，MgO，CeO2）催化剂，以甲烷-二氧化碳重整反应评价其催化性能，并采用XRD、H2-TPR、BET和TG对催化剂的微观结构进行表征。结合催化剂的性能评价结果和表征结果，探讨不同助剂对镍基催化剂性能的改善效果及机制。通过开设该实验，可以让学生了解化工学科的前沿知识以及现代分析技术的基本原理和用途，掌握专业的实验操作、数据处理和谱图绘制方法，提高学生的专业素养和综合能力。     

Experimental investigation of effects of airflows on plasma-assisted combustion actuator characteristics

The effects of the airflow on plasma-assisted combustion actuator(PACA) characteristics are studied in detail. The plasma is characterized electrically, as well as optically with a spectrometer. Our results show that the airflow has an obvious influence on the PACA characteristics. The breakdown voltage and vibrational temperature decrease, while the discharge power increases compared with the stationary airflow. The memory effect of metastable state species and the transportation characteristics of charged particles in microdischarge channel are the dominant causes for the variations of the breakdown voltage and discharge power, respectively, and the vibrational temperature calculated in this work can describe the electron energy of the dielectric barrier discharge plasma in PACA. These results offer new perspectives for the use of PACA in plasma-assisted combustion.