稀土离子掺杂Ⅲ-Ⅴ族半导体的发光

稀土离子掺杂Ⅲ-Ⅴ族半导体的发光是近年来开展起来的新的研究领域.在GaAs,InP和GaP等材料中,用离子注入、LPE、MBE、MOCVD以及单晶生长等方法掺杂Er、Yb和Nd等稀土离子,得到了尖锐稀土离子的特征发光.这些发光来自占据正常立方格点和非立方格点的稀土离子的内部4f能级跃迁,其发光行为与掺杂条件关系很大.这种稀土一半导体材料已开始用来制备具有稳定发射波长的发光和激光器件.     

有机薄膜电致发光器件载流子注入和传输性质的研究

制备了不同电极、不同厚度、以8-羟基喹啉铝螯合物(Alq3)为发光层的有机薄膜电致发光(TFEL)器件。分析了它们的电流密度-电压关系。不同阳极器件的电流变化很大,而改变阴极时电流密度的变化较小,说明电流以空穴为主。根据不同阴极器件的电致发光效率的比较,说明电子是决定器件电致发光效率的少数载流子。从不同厚度的器件的结果讨论了载流子的传输性质,认为在ITO/Alq3/Al器件中的电流符合陷阱限制的空间电荷电流.     

取代环戊二烯锆、铪络合物光解活泼自由基的ESR研究

本文用自旋捕捉术技与ESR相结合的方法,研究取代环成二烯锆、铪络物(RC₅H₄)₂ZrCl₂(R=H,CH₃,C₃H₇,C₄H₉,C₅H₁₁,C₆H₁₁)及(RC₅H₄)₂HfCl₂(R=CH₃,C₂H₅,C₃H₇)光解的活泼自由基。结果表明,取代环成二烯锆、铪络合物与取代环戊二烯钛结合物光解机理相同,即光解初级过程是M-(RC₅H₄)(M=Ti,Zr,Hf)π键的均裂。其差别在于RCpMCl₂(M=Zr,Hf)可为PBN及ND捕获,并后者的加合物表现出氯核的分裂。     

取代吡啶衍生物的13C NMR谱研究

本文测试了三十三个α、β、γ单取代吡啶和二、三取代吡啶衍生物的¹³C NMR谱,归属了全部¹³C NMR谱线。由其¹³C NMR谱线变化规律,研究和总结出各类碳数大于2的烷基取代基对α、β、γ单取代吡啶环碳化学位移的经验取代参数和吡啶环作为一个官能团对烷烃衍生物的取代效应,讨论了单烷基和多烷基吡啶的取代基加和规律。     

Evaluation of negative bias temperature instability in ultra-thin gate oxide pMOSFETs using a new on-line PDO method

A new on-line methodology is used to characterize the negative bias temperature instability (NBTI) without inherent recovery. Saturation drain voltage shift and mobility shift are extracted by I_D-V_D characterizations, which were measured before stress, and after every certain stress phase, using the proportional differential operator (PDO) method. The new on-line methodology avoids the mobility linearity assumption as compared with the previous on-the-fly method. It is found that both reaction--diffusion and charge-injection processes are important in NBTI effect under either DC or AC stress. A similar activation energy, 0.15 eV, occurred in both DC and AC NBTI processes. Also degradation rate factor is independent of temperature below 90\du\ and sharply increases above it. The frequency dependence of NBTI degradation shows that NBTI degradation is independent of frequencies. The carrier tunnelling and reaction--diffusion mechanisms exist simultaneously in NBTI degradation of sub-micron pMOSFETs, and the carrier tunnelling dominates the earlier NBTI stage and the reaction--diffusion mechanism follows when the generation rate of traps caused by carrier tunnelling reaches its maximum.     

Effect of ultrasound on adsorption of Geniposide on polymeric resin

The effects of pulse ultrasound with different pulse parameter on the adsorption isotherm and kinetics of Geniposide on Resin 1300 were studied. And the mass transfer model describing the adsorption process was constructed. Amount of Geniposide adsorbed on Resin 1300 in the presence of ultrasound is lower than that in the absence of ultrasound. At our experimental conditions, the adsorption equilibrium constant decreases with increasing ultrasonic intensity and pulse duty ratio, and with decreasing pulse period. In addition, pulse ultrasound can enhance both liquid film diffusion and intraparticle diffusion, and the intensification of liquid film diffusion with pulse ultrasound is stronger than that of intraparticle diffusion. The intraparticle diffusion coefficient D(e)/R2 increases with increasing ultrasonic intensity and pulse duty ratio, and with decreasing pulse period.     

SiO2-羟基表面上金属原子的第一性原理研究

采用第一性原理方法研究了SiO2-羟基表面上几种金属原子的吸附性质,发现In和Ga在SiO2-羟基表面上的结合很弱,而Fe,Co,Ni在该表面上与Si,O形成强的化学键.等势能面和扩散势垒计算表明In(Ga)的扩散激活能只有0.1-0.3 eV,表明这两种原子容易在表面上扩散.这些结果可以定性地解释纳米合成中的一些实验现象.     

Fourier-domain low-coherence interferometry for differential mode delay analysis of an optical fiber

We propose a novel mode analysis and differential mode delay measurement method for an optical fiber using Fourier-domain low-coherence interferometry. A spectral interferometer based on a Mach-Zehnder interferometer setup was used with a broadband source and an optical spectrum analyzer to detect relative temporal delays between the guided modes of a few-mode optical fiber by analyzing spectral interference signals. We have shown that experimental results of the proposed method agree well with those results obtained by using a conventional time-domain measurement method. We have demonstrated that this new mode analysis technique has high sensitivity (<60 dB) and very good resolution (<1 ps/m).