Na2O掺杂C12A7材料的结构及其抗菌性能

本文利用溶胶-凝胶方法制备了Na2O掺杂的C12A7(12CaO.7Al2O3-Na2O)材料,通过X-射线衍射(XRD)、电子顺磁共振(EPR)、电感等离子体耦合-原子发射光谱(ICP-AES)和飞行时间质谱(TOF-MS)研究了材料结构与性能。选用金黄色葡萄球菌和大肠杆菌为受试菌种,研究了C12A7-Na2O的抗菌性能。结果表明,Na2O掺杂对C12A7的晶体结构以及材料中的氧负离子的浓度没有显著的影响,且C12A7-Na2O材料具有较高的抗菌性能。利用扫描电镜(SEM)对杀菌前后的金黄色葡萄球菌和大肠杆菌的菌体形态进行了观测,初步探讨了C12A7-Na2O的抗菌机理。     

Yb-Er共掺光波导放大器增益特性模拟及优化

为提高光波导放大器的增益特性,从Yb-Er共掺系统的能级结构及能量传递过程出发,建立了Yb-Er共掺光波导放大器增益的理论模型,对增益特性进行数值模拟;讨论了铒离子的掺杂浓度、泵浦光功率和信号光功率等因素对光波导放大器增益的影响,并进行优化。数值模拟结果表明:当波导长度小于其最佳值时,增益随铒离子的掺杂浓度和泵浦光功率的增加而显著增大;超过最佳波导长度,增益随之下降;泵浦光功率一致,信号光功率增强时,增益下降。抽运功率为70 mW时,长度为2.24 cm的光波导放大器,单位长度增益为4.73 dB/cm,该结果与实验数据基本吻合。     

Mottness,phase string,and high-Tc superconductivity

It is a great discovery in physics of the twentieth century that the elementary particles in nature are dictated by gauge forces, characterized by a nonintegrable phase factor that an elementary particle of charge $q$ acquires from $A$ to $B$ points: $P \exp \left( \text{i} \frac q {\hbar c}\int_A^B A_{\mu}\text{d} x^{\mu}\right),$ where $A_{\mu}$ is the gauge potential and $P$ stands for path ordering. In a many-body system of strongly correlated electrons, if the so-called Mott gap is opened up by interaction, the corresponding Hilbert space will be fundamentally changed. A novel nonintegrable phase factor known as phase-string will appear and replace the conventional Fermi statistics to dictate the low-lying physics. Protected by the Mott gap, which is clearly identified in the high-$T_{\rm c}$ cuprate with a magnitude $> 1.5$ eV, such a singular phase factor can enforce a fractionalization of the electrons, leading to a dual world of exotic elementary particles with a topological gauge structure. A non-Fermi-liquid "parent" state will emerge, in which the gapless Landau quasiparticle is only partially robust around the so-called Fermi arc regions, while the main dynamics are dominated by two types of gapped spinons. Antiferromagnetism, superconductivity, and a Fermi liquid with full Fermi surface can be regarded as the low-temperature instabilities of this new parent state. Both numerics and experiments provide direct evidence for such an emergent physics of the Mottness, which lies in the core of a high-$T_{\rm c}$ superconducting mechanism.     

Synthesis of Porous,Nitrogen‐Doped Adsorption/Diffusion Carbonaceous Membranes for Efficient CO2 Separation

A porous, nitrogen‐doped carbonaceous free‐standing membrane (TFMT‐550) is prepared by a facile template‐free method using letrozole as an intermediate to a triazole‐functionalized‐triazine framework, followed by carbonization. Such adsorption/diffusion membranes exhibit good separation performance of CO₂ over N₂ and surpassing the most recent Robeson upper bound. An exceptional ideal CO₂/N₂ permselectivity of 47.5 was achieved with a good CO₂ permeability of 2.40 × 10⁻¹³ mol m m⁻² s⁻¹ Pa⁻¹. The latter results arise from the presence of micropores, narrow distribution of small mesopores and from the strong dipole–quadrupole interactions between the large quadrupole moment of CO₂ molecules and the polar sites associated with N groups (e.g., triazine units) within the framework.     

Fast synthesis of Cu‐doped ZnO nanosheets at ambient condition

A new, fast and low cost method to produce Cu‐doped ZnO nanosheets is reported for the first time in this paper. Zinc foil specimens were immersed into CuSO₄ aqueous solutions with various concentrations for 3 seconds and then dried at ambient condition. The immersed specimens were characterized with a scanning electron microscope, an X‐ray diffractometer and a transmission electron microscope. The results show that Cu‐doped ZnO nanosheets with a multilayer structure on a cupper layer are formed. Cu‐doped ZnO nanosheets show hexagonal crystalline structure and comprises polycrystalline grains with diameters of 5∼10 nm. A physical modal is suggested to explain the prepared Cu‐doped ZnO nanosheet structure, based on the chemical reactions and a metallurgical cell.     

Ion Beam Mixing for Silicide Formation

Refractory metal silcides are under intensive investigation to be used as contact and interconnect materials in VLSI circuits. Ion beam mixing has been proposed as a technique for simultaneous doping and metal silicide formution. This work presents a theoretical model for calculating the different parameters required for ion beam mixing through ion implantation. The minimum ion beam energy and dose for complete mixing is calculated. A plot of the obtained energy-dose relation shows that the dose increases linearly with energy. The dose-silicide thickness relation is also plotted. It is found that the thickness of the formed metal silicide increases linearly with the square root of the applied dose. A good agreement is found between the values and relations of the proposed model and experimental results.     

The electronic and optical properties of Cu doped CdI2

Based on the density functional pseudopotential method, the electronic structures and the optical properties of CdI₂ doped with Cu are investigated in detail. The calculation results indicate that the defect of Cu(Cd) exists steadily with a certain solubility. For the Cu doped CdI₂, the new highly localized impurity bands induced by Cu 3d states lie just across the Fermi energy at the top of the valence band. The doping of Cu induces reduction of band gap of CdI₂; red shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change in band gaps. Moreover, the study of the reflection spectrum and the loss function shows that the doped Cu is responsible for the increased reflection peak intensity and the red shift of the plasma resonant frequency of CdI₂.     

Gain clamped L-band EDFA with forward–backward pumping scheme using fiber Bragg grating

The paper proposes a novel two stage L-band erbium doped fiber amplifier with forward–backward pumping scheme for transmission of 32 wavelength division multiplexed (WDM) channels. It is gain clamped with an in-line fiber Bragg grating (FBG) to provide flat gain over 45 nm by restricting and reutilizing amplified spontaneous emission (ASE). We demonstrate that it provides an efficient small signal gain with minimum noise figure of over 20 dB and 5.5 dB, respectively, in the L-band region (1565–1610 nm) by comparing with its forward and backward pumped counterparts with fixed Er³⁺ fiber length of 20 m for −30 dBm/channel input power. We also obtain the gain and noise figure dependence as a function of each of the Er³⁺ fiber lengths, pump power (both 1480 and 980 nm), and temperature. Hence a 10 nm region (1580–1590 nm) has been acknowledged where temperature variations become constricted for 30 °C variations (15–45 °C).     

Mg含量对Mg_xZn_(1-x)O∶Ga薄膜电学性质的影响

通过金属有机物化学气相沉积法制备了不同Mg组分的MgxZn1-xO∶Ga(x=0,0.03,0.14)薄膜。透射谱中MgxZn1-xO∶Ga薄膜的光学带隙随x增大而出现的蓝移证实了Mg在Zn O晶格中的替位掺入。薄膜上金叉指电极间的变温I-V曲线显示,在同等温度下,Ga掺杂MgxZn1-xO薄膜的电阻率随着x值的增大而逐渐升高。这是由于Mg组分增大使材料的导带底显著上升,Ga的施主能级深度增大,导致n型载流子浓度降低。根据I-V曲线计算了270 K温度下MgxZn1-xO∶Ga薄膜的浅能级施主深度。与x=0,0.03,0.14对应的施主能级深度分别为45.3,58.5,65 me V,说明随着薄膜Mg含量的升高,Ga的施主能级深度有增加的趋势。     

高重复频率、单模纳秒脉冲全光纤激光器

报道了一种基于主振荡放大技术的全光纤脉冲激光器.种子激光器使用直接调制的单纵模半导体激光器,其输出波长为1 063.8 nm,重复频率100 kHz~10 MHz连续可调谐,光纤放大器采用了多级放大器级联的方法.在重复频率100 kHz、脉冲宽度5 ns时,激光器获得了平均功率为1.2 W,峰值功率为2.4 kW的单横模激光脉冲输出.