四配位有机锗化合物的13C NMR表征

对三十多年所发表的四配位有机锗化合物的核磁共振碳谱进行了综合评论.即对饱和烃基锗、不饱和烃基锗、锗杂环化合物、有机锗卤化合物、有机锗醚化合物这五类有机锗化合物的¹³C NMR数据作了系统的归纳,对光谱特征进行了总结.     

线状锗等离子体X射线线谱的时间分辨测量

用自行研制的X射线条纹晶体谱仪首次测量了线状锗等离子体的X射线时间分辨谱。给出了类Ne-锗L线共振线的时间演化过程,并用类Ne-锗L线共振线与其双电子俘获伴线的相对强度比粗估了锗等离子体的电子温度及其随时间的变化,实验给出了X光激光增益区介质的电子温度为400～760eV,同时给出了电子温度保持相对恒定的时间不小于90ps(电子温度变化小于2％)。     

激光等离子体电子温度的时间分辨诊断

本文描述在LF-11激光装置上进行的线状锗等离子体电子温度时间分辨诊断的实验。在实验中利用时间分辨X射线晶体谱仪测量了线状锗等离子体X射线的时间分辨谱,并借助碰撞辐射模型(CR模型),由类Ne锗L线特征线相对强度比确定出锗等离子体的电子温度及其时间演化过程。并与用部分局部热平衡模型(PLTE)得出的结果做了比较。     

激光锗等离子体电子密度诊断

本工作测量了激光加热锗等离子体XUV光谱,对所测得的Ge ⅩⅫ谱线进行了辨认和分类。通过对各谱线的考察,找出了对电严密度敏感,对电子温度不敏感,波长在20nm左右的类钠离子3p—3d及3s—3p跃迁线,收集和计算了所需参数,给出谱线强度比随电子密度变化曲线,根据谱线强度比推导了锗等离子体的电子密度,并与理论计算结果进行了比较,二者符合较好。     

X光激光实验中的等离子体状态诊断

在LF-12激光装置上,将500～600J、约1.5ns脉冲宽度的Nd玻璃激光聚焦成约120μm宽、20mm长的线作用到1mm厚的锗平面靶上。在靶室内设置具有空间分辨本领的平晶谱仪(测量波长范围在0.6～0.9nm)诊断锗等离子体状态。用2p-nd(n≥4)能级跃迁的类Ne离子谱线间的相对强度比估计等离子体电子温度在400～600eV。在实验中测到的线谱主要是类Ne GeXXⅢ离子产生的,类F GeXXⅣ离子产生的谱线次之,类Na GeXXⅡ离子产生的谱线比较弱。并且初步观察到线状等离子体轴向分布均匀性和横向离子分布特征。     

槲皮素锗的合成及表征

槲皮素在碱溶液中,与锗离子反应生成槲皮素锗并通过元素分析、紫外光谱、红外光谱和热差分析对槲皮素锗进行了表征.     

柱状锗等离子体状态的时空分辨诊断

在四靶串接X光激光实验中,用时间分辨晶体谱仪记录了类Ne锗共振线及其类Na伴线的时间扫描特性。测出了这些谱线的辐射持续时间(FWHM)约为0.95ns。考察了锗等离子体电子温度T_e随时间的演化,观测到T_e≥400eV的维持时间大于1.2ns。用空间分辨晶体谱仪诊断得到锗等离子体电子温度T_e和电子密度n_e的轴向分布,其平均值T_e=4.9×10~2eV,n_e=1.2×10~(20)/cm~3。     

简并态锗在大注入下的自发辐射谱模拟

基于费米狄拉克模型模拟了应变、温度以及掺杂对简并态锗的直接带自发辐射谱的影响.随着温度升高,更多的电子被激发到导带中,使得锗自发辐射谱的峰值强度和积分强度随温度的升高而增大.对自发辐射谱峰值强度的m因子进行计算,结果表明张应变可以显著提高锗自发辐射的温度稳定性.在相同应变水平下,由Γ-hh跃迁引起的自发辐射谱峰值强度大于Γ-lh跃迁引起的自发辐射谱峰值强度,但二者的积分强度几乎相等.此外,计算结果还证明了n型掺杂能显著提高锗的自发辐射强度.以上结果对于研究简并态半导体的自发辐射性质有重要的参考意义.     

锗掺杂聚合物及其泡沫的制备与表征北大核心CSCD

采用稳定自由基聚合法合成了锗掺杂聚苯乙烯类聚合物,并利用聚合物溶液的热致相分离原理和冷冻干燥技术制备出具有多孔结构的锗掺杂泡沫材料。通过核磁共振氢谱、等离子体发射光谱及扫描电镜等测试手段表征了聚合物分子和泡沫结构。结果表明,聚合物分子具有极窄的分子量分布,锗掺杂原子分数为2．6％;泡沫具有多孔网络结构和薄片状骨架,骨架间的孔洞尺寸为1～10／zm,泡沫骨架随密度的降低趋于细化,孔洞变大。     

X光激光研究中的等离子体状态诊断

在预作X光激光增益介质的中Z靶(象锗靶)中均匀掺人少量的低Z元素(象铝),利用后者的类氦谱线强度比确定了等离子体状态;同时还在PLTE近似下由锗线的强度比确定了等离子体状态,二者基本吻合。     

Ab initio determination of crystal lattice constants and thermal expansion for germanium isotopes

The temperature dependence of the equilibrium lattice constants for five isotopically pure Ge crystals (⁷⁰Ge, ⁷²Ge, ⁷³Ge, ⁷⁴Ge and ⁷⁶Ge) and naturally occurring Ge were calculated from ab initio electronic theory within the quasiharmonic approximation. It is shown that at very low temperature, calculations including zero point motions contribution to the free energy correctly reproduced the experimental unit cell parameters for the five isotopes. For ⁷⁰Ge, ⁷⁴Ge, ⁷⁶Ge and naturally occurring Ge, the predicted thermal expansion coefficients agree very well with experiments. The calculated thermal expansitivity for ⁷³Ge does not agree well with experiment. It is speculated that this anomaly may due to the non-zero nuclear spin of the ⁷³Ge isotope.     

掺杂对多层Ge/Si(001)量子点光致发光的影响

利用超高真空化学气相沉积设备, 在Si (001) 衬底上外延生长了多个四层Ge/Si量子点样品. 通过原位掺杂的方法, 对不同样品中的Ge/Si量子点分别进行了未掺杂、磷掺杂和硼掺杂. 相比未掺杂的样品, 磷掺杂不影响Ge/Si量子点的表面形貌, 但可以有效增强其室温光致发光; 而硼掺杂会增强Ge/Si量子点的合并, 降低小尺寸Ge/Si量子点的密度, 但其光致发光会减弱. 磷掺杂增强Ge/Si量子点光致发光的原因是, 磷掺杂为Ge/Si量子点提供了更多参与辐射复合的电子. 关键词： Ge/Si量子点 磷掺杂 光致发光     

Ge/Si混合物纳米薄膜中Ge钠米颗粒氧化态的XPS研究(英文)

pacc:7300,3320R TheoxidationstatesofGenanoparticlesin thesurfacelayerofGe/SifilmwerestudiedbyX-rayphotoelectronspectroscopy.Newfeatures appearedatthehighbindingenergysideofthe XPSGe3dpeakwhensampleswereannealedin atmosphere,whichwerecausedbythelargein ter…     

Theoretical analysis of fluorine-passivated germanium surface for high-k/Ge gate stack by molecular orbital method

Energy state and coordination of fluorine (F)-passivated Ge surface have been theoretically analyzed by semi-empirical molecular orbital method in comparison with hydrogen-passivated Ge surface to predict usefulness of F for passivation element and surface stabilization. Heat of formation for the reaction of F atoms and Ge layer system decreased simultaneously without energy barrier. Resultantly, F-Ge bonds were formed on Ge layer system and Ge surface dangling bonds were passivated by F dissimilar to the reaction of H atoms and Ge layer system. Furthermore, it was confirmed experimentally that the electrical properties of HfO₂/Ge gate stack were improved by F₂-ambient treatment of Ge substrate prior to HfO₂ deposition. It is concluded that F-passivation of Ge surface is useful in making stable and low-defective Ge substrate for high-k dielectric layer deposition.     

In Situ Transmission Electron Microscopy Observation of Melted Germanium Encapsulated in Multilayer Graphene

Germanene is a two-dimensional germanium (Ge) analogous of graphene, and its unique topological properties are expected to make it a material for next-generation electronics. However, no germanene electronic devices have yet been reported. One of the reasons for this is that germanene is easily oxidized in air due to its lack of chemical stability. Therefore, growing germanene at solid interfaces where it is not oxidized is one of the key steps for realizing electronic devices based on germanene. In this study, the behavior of Ge at the solid interface at high temperatures is observed by transmission electron microscopy (TEM). To achieve such in situ heating TEM observation, this work fabricates a graphene/Ge/graphene encapsulated structure. In situ heating TEM experiments reveal that Ge like droplets move and coalesce with other Ge droplets, indicating that Ge remains as a liquid phase between graphene layers at temperatures higher than the Ge melting point. It is also observed that Ge droplets incorporate the surrounding amorphous Ge as Ge nuclei, thereby increasing its size (domain growth). These results indicate that Ge crystals can be grown at the interface of van der Waals materials, which will be important for future germanene growth at solid interfaces.     

Beiträge zu den Niveauschemata der Ge-Isotope71Ge,73Ge,74Ge und75Ge aus der Untersuchung von (n, γ)-Reaktionen in natürlichem Germanium

Low energy γ-spectra from neutron capture in natural germanium have been studied with several high resolution Ge(Li)-detectors. Measurements have been made with two different target configurations. In the first measurement a normal Ge-target was irradiated with neutrons; no neutrons were allowed to enter the Ge(Li)-detector. In the second measurement the Ge(Li)-detector was used simultaneously as target and as γ- ande ^?-detector. By combination of the results convertion coefficients of several transitions in⁷³Ge have been determined. Several unknown low energy transitions in Ge isotopes have been found with the aid of the second method. The level schemes of⁷¹Ge,⁷³Ge,⁷⁴Ge and⁷⁵Ge have been revised by means of coincidence measurements with a Ge(Li)-Ge(Li)-coincidence system of high efficiency and resolution.     

Formation mechanism of Ge nanocrystals embedded in SiO2 studied by fluorescence x-ray absorption fine structure

This paper reports that the Ge nanocrystals embedded in SiO2 matrix are grown on Si（100） and quartz-glass substrates, and the formation mechanism is systematically studied by using fluorescence x-ray absorption fine structure （XAFS）. It is found that the formation of Ge nanocrystals strongly depends on the properties of substrate materials. In the as-prepared samples with Ge molar content of 60%, Ge atoms exist in amorphous Ge （about 36%） and GeO2 （about 24%） phases. At the annealing temperature of 1073 K, on the quartz-glass substrate Ge nanocrystals are generated from crystallization of amorphous Ge, rather than from the direct decomposition of GeO2 in the as-deposited sample. However, on the Si（100） substrate, the Ge nanocrystals are generated partly from crystallization of amorphous Ge, and partly from GeO2 phases through the permutation reaction with Si substrate. Quantitative analysis reveals that about 10% of GeO2 in the as-prepared sample are permuted with Si wafer to form Ge nanocrystals.     

Ge(SiO2)n团簇结构和电子性质的密度泛函理论研究

采用密度泛函理论中的广义梯度近似(GGA)对Ge(SiO2)n (n = 1—7)团簇的几何构型进行优化,并对能量、频率和电子性质进行了计算。 结果表明,Ge(SiO2)n的最低能量结构是在(SiO2)n端位O原子以及近邻端位O原子的Si原子上吸附一个Ge原子优化得到;随着锗原子数的增加,增加的锗原子易与原来的锗原子形成锗团簇。掺杂锗原子后团簇的能隙比(SiO2)n团簇的能隙小,当多个Ge原子掺杂到(SiO2)3团簇时,其能隙随着Ge原子个数的增加出现了振荡,Gem(SiO2)3的能隙从可见光区到近红外光区变化。二阶能量差分、分裂能表明Ge(SiO2)2和Ge(SiO2)5团簇是稳定的。     

Room temperature oxidation of Cu(3)Ge films grown on Si and Si(1-x)Ge(x) substrates

Room temperature oxidation of Cu3Ge films grown on Si, Si(0.85)Ge(0.15) and Si(0.52)Ge(0.48) substrates, respectively, at a temperature of 200-300 degrees C was studied using transmission electron microscopy (TEM) in conjunction with energy dispersive spectrometry (EDS) and scanning electron microscopy (SEM). For Cu(3)Ge films grown at 200 degrees C and subsequently exposed in air for 1 week oxide protrusions and oxide networks appeared in the film surface and grain boundaries of Cu(3)Ge, respectively. At room temperature O from air and Si from the substrate, diffused along the grain boundaries of Cu(3)Ge to react with Cu(3)Ge grains, initiating the Cu(3)Si-catalyzed oxidation. Cu(3)Ge films are superior to Cu(3)(Si(1-x)Gex) films in retarding Cu(3)Si-catalyzed oxidation. Annealing at 300 degrees C allowed Si diffusion from the substrate into the Cu(3)Ge overlayer to form Cu(3)(Si(1-x)Gex), enhancing the Cu(3)Si-catalyzed oxidation rate. In the present study, Cu(3)Ge films grown on Si(0.52)Ge(0.48) at 200 degrees C show the best resistance to room temperature oxidation because higher Ge concentration in the substrate and lower temperature annealing can more effectively retard Si diffusion from the substrate into the Cu(3)Ge overlayer, and hence reduce the Cu(3)Si-catalyzed oxidation rate.     

Photoluminescence and infrared absorption studies of Ge doped with Mg

The photoluminescence spectrum of Ge doped with the double acceptor Mg reveals lines due to both bound excitons and bound multiexciton complexes, which are in some ways similar to those previously reported for Ge:Be and Ge:Zn. As in Ge:Zn, the Ge:Mg bound exciton line was found to be a doublet, showing that the Mg double acceptor in Ge also has a split ground state. Further evidence for this ground state splitting is found from the temperature dependence of the infrared absorption spectrum of the Mg double acceptor.