GaAs／GaInNAsSb超晶格性能的影响

用Keafing的价力场(valence force field)模型和蒙特卡罗方法计算了GaAs／GaInNAsSb超晶格中键的分布、原子的精确位置以及应变．用折叠谱(foldedspectrummethod)合Williamson经验赝势法计算了GaAs／GaInNAsSb超晶格应变条件下的电子结构．讨论了N和Sb原子以及超晶格单分子层数对电子结构的影响．发现导带底电子态在N原子周围的局域化减小了光跃迁矩阵元，从而影响了该超晶格的发光性能．计算并讨论了超晶格的电子和空穴的有效质量．     

INFLUENCE OF SPIN AND CHARGE FLUCTUATIONS ON THE HIGH-Tc SUPERCONDUCTIVITY

In the framework of the weak coupling theory of superconductivity, we have proved that spin and charge fluctuations in the high-T_c superconductors can pro-duce respectively, pair-breaking and pair-forming effects on the superconductivity resulting from the "generalized BCS mechanism". With the coupling constant for spin fluctuations larger than that for charge fluctuations, they combine to produce a temperature-dependent effective pair-breaking effect, which makes T_c decrease more rapidly than Δ(0), the superconducting gap at T=0, and therefore, enhances the ratio 2Δ(0)/T_c. This provides a reasonable physical interpretation for the relevant experimental results.     

大孔磷酸树脂吸附稼的研究

本文报道了大孔膦酸树脂对镓(Ⅲ)的吸附及洗脱条件试验,报道了混合体系中镓对共存离子的分离系数,以及树脂对稼的吸附容量和络合比,并探讨了膦酸树脂吸附镓(Ⅲ)的机理。红外光谱证明,树脂吸附Ga(Ⅲ)的过程,p-OH基中的H与Ga(Ⅲ)发生了交换,而p=0基参与配位,形成了配位化合物。     

GaAs基GaAsSb/GaInAs双层量子阱的发光

嵌入GaAs中的GaAsSb／GaInAs量子阱因其在1．3～1．5μm光通信波段发光的潜力而受到关注,我们研究了一系列MBE生长的GaAsSb／GaInAs量子阱样品的光致发光,发现所有样品在室温下都出现了一个较强的、波长在1．3μm附近的低能峰和一个较弱的高能峰。变温及变激发功率的荧光谱测量研究发现,高能峰只有在150K以上的测试条件下才能观测到,并且其相对强度随着温度的升高而增加,其调制光谱显示出第一类跃迁的特征。他们建立了理论模型,计算的结果支持将这一发光峰指派为GaInAs层内电子的基态与重空穴激发态间的跃迁,并与实验数据吻合得很好。同时初步讨论了改善1．3μm的低能峰发光的方法。     

Molecular Beam Epitaxy Growth and Photoluminescence of Type-Ⅱ （GaAs1-xSbx／InyGa1-yAs）／GaAs Bilayer Quantum Well

We report a systematical study on the molecular beam epitaxy growth and optical property of (GaAs1-xSbx/InyGa1-yAs)/GaAs bilayer quantum we]] (BQW) structures. It is shown that the growth temperature of the wells and the sequence of layer growth have significant influence on the interface quality and the subsequent photoluminescence (PL) spectra. Under optimized growth conditions, three high-quality (GaAsSb0.29/In0.4 GaAs)/GaAs BQWs are successfully fabricated and a room temperature PL at 1314 nm is observed. The transition mechanism in the BQW is also discussed by photoluminescence and photoreflectance measurements. The results confirm experimentally a type-Ⅱ band alignment of the interface between the GaAsSb and InGaAs layers.     

N,Sb和单分子层数对GaAs/GaInNAsSb超晶格性能的影响

用Keating的价力场 (valenceforcefield)模型和蒙特卡罗方法计算了GaAs GaInNAsSb超晶格中键的分布、原子的精确位置以及应变 .用折叠谱法 (foldedspectrummethod)结合Williamson经验赝势法计算了GaAs GaInNAsSb超晶格应变条件下的电子结构 .讨论了N和Sb原子以及超晶格单分子层数对电子结构的影响 .发现导带底电子态在N原子周围的局域化减小了光跃迁矩阵元 ,从而影响了该超晶格的发光性能 .计算并讨论了超晶格的电子和空穴的有效质量 .     

聚合物中光激发在电场作用下的转化

用动力学方法模拟了在聚合物中观察到的“场诱导电荷产生”现象,给出了聚合物链上键结构和电荷分布随时间的演变过程,并确定了激子变为极化子对的弛豫时间. 关键词：     

分子模拟研究烯二炔环发色团分子从新制癌菌素的释放机理

烯二炔环发色团分子(Enediyne ring chromophore)虽然对DNA具有较好的切割性, 但由于它缺乏稳定性, 必须与蛋白结合形成非共价化合物(即新制癌菌素: Neocarzinostatin)才能进入细胞发挥生理作用. 作为一种已在临床上应用的抗肿瘤药物, 烯二炔环发色团分子从结合蛋白释放到细胞过程仍然是不清楚的. 以新制癌菌素复合物和对应的结合蛋白的X射线衍射结构作为研究对象, 运用分子动力学的模拟和拉伸动力学方法研究烯二炔环发色团分子从结合蛋白中释放的机理. 模拟结果表明从萘酸基方向释放可能是烯二炔环发色团分子最佳的释放路径.     

高分子中双激子态对外电场的线性响应

在外电场中,非简并基态共轭高分子中的双激子具有反向极化的奇异特性.利用响应函数求得高分子链的双激子态在任意频率下的动态极化率χ(ω),并通过求ω→0极限,给出双激子态的静态极化率χ,证实了χ确实为负值.并与激子态和基态作了比较,分析了分子负极化率的起因.考察了响应函数在低频时的行为,指出激子和双激子的激发浓度增大会导致材料折射率n(ω)向不同方向变化. 关键词：     

INFLUENCE OF SPIN AND CHARGE FLUCTUATIONS ON THE HIGH-Tc SUPERCONDUCTIVITY

In the framework of the weak coupling theory of superconductivity, we have proved that spin and charge fluctuations in the high-T_c superconductors can pro-duce respectively, pair-breaking and pair-forming effects on the superconductivity resulting from the "generalized BCS mechanism". With the coupling constant for spin fluctuations larger than that for charge fluctuations, they combine to produce a temperature-dependent effective pair-breaking effect, which makes T_c decrease more rapidly than Δ(0), the superconducting gap at T=0, and therefore, enhances the ratio 2Δ(0)/T_c. This provides a reasonable physical interpretation for the relevant experimental results.