单晶金刚石氢终端场效应晶体管特性

基于微波等离子体化学气相淀积生长的单晶金刚石制作了栅长为2μm的耗尽型氢终端金刚石场效应晶体管,并对器件特性进行了分析.器件的饱和漏电流在栅压为-6 V时达到了96 mA/mm,但是在-6 V时栅泄漏电流过大.在-3.5 V的安全工作栅压下,饱和漏电流达到了77 mA/mm.在器件的饱和区,宽5.9 V的栅电压范围内,跨导随着栅电压的增加而近线性增大到30 mS/mm.通过对器件导通电阻和电容-电压特性的分析,氢终端单晶金刚石的二维空穴气浓度达到了1.99×10~(13)cm~(-2),并且迁移率和载流子浓度均随着栅压向正偏方向的移动而逐渐增大.分析认为,沟道中高密度的载流子、大的栅电容以及迁移率的逐渐增加是引起跨导在很大的栅压范围内近线性增加的原因.     

受污染混沌信号的协同滤波降噪

根据混沌吸引子的自相似分形特性,提出了一种利用协同滤波重构受污染混沌信号的降噪算法.所设计的降噪算法通过对相似片段的分组将一维混沌信号的降噪转化为一个二维联合滤波问题;然后,在二维变换域用阈值法衰减噪声;最后,通过反变换获得原始信号的估计.由于分组中的相似片段具有良好的相关性,与直接在一维变换域做阈值降噪相比,分组的二维变换能获得原信号更稀疏的表示,更好地抑制噪声.仿真结果表明,该算法对原始混沌信号的重构精度和信噪比的提升都优于小波阈值、局部曲线拟合等现有的混沌信号降噪方法,对相图的还原质量也更好.     

170 keV Proton radiation effects on low-frequency noise of bipolar junction transistors

In this paper, the electrical properties and low-frequency noise for bipolar junction transistors irradiated by 170?keV proton are examined. The result indicates that for the sample under proton irradiation with fluence 1.25?×?10^14?p/cm², base current I_B in low bias range (V_BE < 0.7?V) increases due to superimposition of radiation-induced recombination current, while the gain decreases significantly. Meanwhile, the low-frequency noise increases in the proton-irradiated sample. By analysis of evolution of parameters extracted from low-frequency noise power spectra, it is demonstrated that radiation-induced noise is mainly originated from carrier fluctuation modulated by generation–recombination centers (G–R centers) located at the interface of Si/SiO₂, which are introduced by proton-radiation-induced defects. It is also confirmed that the electrical properties and noise behavior of irradiated sample are mostly affected by the carrier recombination process caused by G–R centers at the interface of Si/SiO₂ than by G–R centers in EB junctions.     

Effect of bromine substituent on optical properties of aryl compounds

Substituents significantly affect optical properties of organic compounds. In this study, a series of organic compounds were synthesized. Ultraviolet‐visible and cyclic voltammetry spectra were determined. The relationships between the number of π electron in an aryl ring and the redshift (and molecular orbital energy levels) were studied. To investigate mechanisms of the bromine substituent effects, theoretical calculations were carried out. Ultraviolet‐visible spectra of bromine‐containing compounds exhibit obvious redshifts (0.04‐0.17 eV) of the maximal absorption wavelengths and enhanced absorbance (11%‐57%) compared with corresponding reference compounds. The lowest unoccupied and highest occupied molecular orbital energy levels of compounds containing bromine substituents are 0.05 to 0.60 and 0.02 to 0.40 eV lower than that of corresponding reference compounds. On the whole, the redshifts and the reduced molecular orbital energy levels caused by bromine substituent decrease with the increase in the number of π electron in an aryl ring. The effects would be attributed to strong p‐π conjugation between p electron in the bromine substituent and π electrons in aryl rings. Therefore, this paper suggests a useful way for tuning optical absorption and molecular orbital energy levels of aryl compounds.     

NASICON型化合物结构的NMR研究

在水热晶化合成一系列NASICON型化合物的基础上,应用固体高分辨³¹P和²⁹Si MAS NMR,研究了几种NASICON化合物的结构,观察其骨架原子P和Si在结构中的状态及分布,并解释了由于在结构中发生取代作用而引起,Si或P的化学位移的变化.     

锑掺杂氧化锡粉体的太赫兹透射特性

以SnCl45H2O和SbCl3为原料,采用液相化学共沉淀法制备锑掺杂氧化锡（ATO）粉体。分析了不同Sb掺杂质量分数条件下,ATO粉体的禁带宽度变化,并对材料在0.2~1.6 THz波段的透射时域和频域谱,以及吸收和屏蔽参数进行了对比分析。结果表明,ATO粉体的禁带宽度随着Sb掺杂量的增加先减小后增大;同时,ATO粉体对THz波的吸收系数随着Sb掺杂量的增加先增大后减小,当Sb掺杂质量分数为9%时,ATO的吸收系数在1.25 THz处达到最大值156.5 cm-1,屏蔽效能在1.24~1.60 THz范围内最高达到45.0 dB。     

Scheme for Generating a Genuine Five-Atom Entangled State in Cavity QED

We propose a scheme for the generation of a genuine five-atom entangled state in cavity QED. In our scheme, the atoms interact simultaneously with a highly detuned cavity mode with the assistance of a strong classical driving field. Thus the scheme is insensitive to both the cavity decay and the thermal field, which is of importance from the experimental point of view.     

拉曼光谱结合偏最小二乘法测定血清胆固醇含量

以日常体检用血清样品为分析对象,采集了其拉曼光谱,波数范围为250～2 400cm-1,并对信号进行归属,与临床传统生化法测定得到的胆固醇含量对比,结合偏最小二乘法建立了血清胆固醇拉曼光谱定量模型(n=73)。结果表明,拉曼光谱能够表征血清中主要化学基团的信息。所建立的血清胆固醇定量校正模型的相关系数R为0.909 6,交叉验证校正标准差(RMSECV)为0.24;检验集(n=17)预测标准差(RMSEP)为0.69,相关系数r为0.926 2。证明了应用拉曼光谱技术结合偏最小二乘法建立血清胆固醇定量模型,用于未知血清样品胆固醇含量无损快速检测是可行的。     

Bi2WO6纳米晶的制备、表征及光催化性能

以硝酸铋、钨酸钠等为原料,利用水热法在150℃下反应24h得到Bi2WO6纳米晶。X射线粉末衍射结果表明,所制备的Bi2WO6属于正交晶系,晶胞参数为a=5.457,b=16.435及c=5.438。XPS结果表明所制造的Bi2WO6纯度较高。研究了分别以水、N,N-二甲基甲酰胺、乙二醇为溶剂时所制备Bi2WO6样品在可见光激发下对罗丹明B的降解活性,结果表明,以乙二醇为溶剂时,Bi2WO6光催化活性最佳,主要是由于在乙二醇中制备的Bi2WO6分散性好,粒径小,对紫外-可见光具有较大波长范围的吸收所致。另外,研究了以水为溶剂时溶液pH及添加表面活性剂等对所制备Bi2WO6光催化活性的影响,结果表明,反应温度为140～150℃,pH在1.0附近及添加SDS后所制备Bi2WO6光催化活性较佳。荧光光谱分析发现,添加表面活性剂的样品发射荧光的强度较弱,表明载流子复合程度低,因而光催化效率高。     

Molecular dynamics study of thermal stress and heat propagation in tungsten under thermal shock

Using molecular dynamics （MD） simulation, we study the thermal shock behavior of tungsten （W）, which has been used for the plasma facing material （PFM） of tokamaks. The thermo-elastic stress wave, corresponding to the collective displacement of atoms, is analyzed with the Lagrangian atomic stress method, of which the reliability is also analyzed. The stress wave velocity corresponds to the speed of sound in the material, which is not dependent on the thermal shock energy. The peak pressure of a normal stress wave increases with the increase of thermal shock energy. We analyze the temperature evolution of the thermal shock region according to the Fourier transformation. It can be seen that the “obvious” velocity of heat propagation is less than the velocity of the stress wave; further, that the thermo-elastic stress wave may contribute little to the transport of kinetic energy. The heat propagation can be described properly by the heat conduction equation. These results may be useful for understanding the process of the thermal shock of tungsten.