Si4团簇电子输运性质的第一性原理计算

采用密度泛函理论和非平衡格林函数相结合的方法对Si₄ 团簇与Au(100)电极空位相连的纳米结点的电子输运性质进行了理论模拟计算, 得到了纳米结点在不同距离下的几何结构、电子结构、电导、透射谱、电荷转移量; 讨论了当距离d_z=12.004 Å时纳米结点的电导、电流随电压的变化关系. 关键词： 密度泛函理论 非平衡格林函数 4团簇')" href="#">Si₄团簇 电子输运     

分子结点电子输运性质的理论研究

采用基于密度泛函理论的非平衡态格林函数方法,研究了Pt-H₂微结点在平衡态和低偏压下的电子输运行为,考察了电极-分子耦合形貌对结点输运性质的影响,并采用费曼路径概念从结点局域轨道出发分析了其输运特性. 发现H₂分子的反键轨道可以参与结点的低偏压电子输运,偏压可以通过改变系统局域分子轨道来影响其输运性质. 关键词： 分子结点 电子输运 非平衡态格林函数方法 透射谱     

C20F20分子电子输运性质的第一性原理研究

利用第一性原理密度泛函理论和非平衡格林函数方法研究了C₂₀F₂₀分子的电子输运性质. 计算得到了C₂₀F₂₀分子的平衡电导为0385 G₀ 其I-V曲线表现出较好的线性特性. 在有限偏压范围内具有较稳定的电导值, 可以用于制备稳恒电阻分子器件. 关键词： 20F₂₀分子')" href="#">C₂₀F₂₀分子 电子输运 分子器件     

金电极下二元化合物氮化镓链结构演化和电导的从头计算（英文）

基于从头密度泛函理论结合非平衡格林函数方法,首次研究了二元化合物GaN链介于两个金电极之间的电子输运性质.模拟了Au-(GaN)_2-Au节点断裂过程,计算了相应的结合能,获得了平衡态电导以及平衡态下节点的投影态密度.此外,计算了平衡态下节点在微小偏压下的电流和电导.结果发现,随着偏压增强,GaN分子链的电导也随之下降.最后给出的伏安特性曲线呈现一个非线性关系,表明节点具有类似半导体的特征.     

Na掺杂对C20H20分子的电子输运性质影响

利用第一性原理密度泛函理论和非平衡格林函数方法研究了Na@C₂₀H₂₀分子的电子输运性质. 计算结果显示它的I-V曲线在偏圧 V范围内表现出了较好的线性特性, 出现了明显的负微分电阻现象, 并得到其平衡电导为0.0101G₀. 通过与Li@C₂₀H₂₀分子对比分析, 发现掺杂Na不仅能提高C₂₀H₂₀分子的电子输运能力, 而且 关键词： 20H₂₀分子')" href="#">Na@C₂₀H₂₀分子 电子输运 负微分电阻     

Au-Si_(60)-Au分子结电子输运性质的理论计算

运用密度泛函理论对Si60团簇的结构进行几何优化,得到基态结构是一个直径为1.131 nm,平均键长为0.239 nm,分子最低未占据轨道与最高占据轨道能量差即能隙值为0.72 eV,具有C1点群的空心笼状结构.然后把它与两半无限的Au(100)-4×4电极相连构成Au-Si60-Au三明治结构分子结点,运用密度泛函理论结合非平衡格林函数的方法对其电子输运性质进行了第一性原理计算.当两电极的距离为1.74 nm时,分子结点的平衡电导为1.93G0(G0=2e2/h),然后在-2.0—2.0 V的电压范围内,计算了不同电压下的电导与电流,得到其I-V曲线成近线性关系,从分子前线轨道与透射谱分析了Si60分子的电子输运特性,讨论了电荷转移量与电导之间的关系.     

耦合形貌对Si4团簇电子输运影响的第一性原理计算

运用密度泛函理论与非平衡格林函数相结合的方法,对Si₄团簇与Au （100）-3×3两电极以顶位-顶位、顶位-空位、空位-空位三种形貌相连构成的Au-Si₄-Au纳米结点的拉伸过程进行第一性原理模拟,计算不同构型纳米结点在不同距离的电导和结合能.讨论耦合形貌、距离对结点电导的影响,结合能的计算表明三种不同耦合形貌结点存在稳定平衡结构,其平衡电导分别为0.71 G₀、0.96 G₀和2.44 G₀,且在-1.2 V~1.2 V的电压范围内,三种不同耦合形貌结点稳定结构表现出类似金属的导电特性,其I-V关系都近似为直线.计算结果表明Si₄团簇与电极的耦合形貌、两极距离对纳米结点电子输运有重要影响.     

Au-Si-Au结点电子输运性质的第一性原理计算

采用密度泛函理论和非平衡格林函数相结合的方法对Au(100)-Si-Au(100) 系统左侧对顶位、右侧对空位的纳米结点的电子输运性质进行了理论模拟计算, 结果得到纳米结点的电导随电极距离(d_z)增大而减小. 在d_z =9.72 Å时, 结点的结合能最低, 结构最稳定, 此时电导为1.227G₀ (G₀=2e²/h), 其电子输运通道主要是Si原子的p_x, p_y和 p_z轨道电子形成的最高占居轨道共振峰; 在外偏压下, 电流-电压曲线表现出线性特征; 随着外加正负电压的增大, 电导略有减小, 且表现出不对称性的变化. 关键词： 硅原子 电子输运 密度泛函理论 非平衡格林函数     

金电极下二元化合物氮化镓链结构演化和电导的从头计算

基于从头密度泛函理论结合非平衡格林函数方法,首次研究了二元化合物GaN链介于两个金电极之间的电子输运性质。模拟了Au-(GaN)2-Au节点断裂过程,计算了相应的结合能,获得了平衡态电导以及平衡态下节点的投影态密度。此外,计算了平衡态下节点在微小偏压下的电流和电导。结果发现,随着偏压增强,GaN分子链的电导也随之下降。最后给出的伏安特性曲线呈现一个非线性关系,表明节点具有类似半导体的特征。     

(CH3)2和(NH2)2基团修饰的齐聚苯乙炔分子电子输运性质研究

采用密度泛函理论和非平衡格林函数相结合的方法研究了S原子作为单、双端基的(CH₃)₂-OPE (齐聚苯乙炔)和(NH₂)₂-OPE分子在金电极间的电子输运性质. 通过第一性原理优化计算获得分子部分稳定结构, 再置于Au电极之间构成两极系统, 然后再优化整个两极系统获得稳定结构. 另外, 通过非平衡格林函数方法计算了两极系统的电子输运性质. 计算结果表明, 不同的修饰基团和桥接方式可以导致两极系统的开关效应、负微分电阻行为和整流行为等不同的电子输运性质. 通过计算不同偏压下的分子体系投影轨道电子分布、透射谱、态密度, 对这些新异的电输运性质出现的机理进行了解释.     

三明治结构Tan(B3N3H6)n+1 团簇的磁性和量子输运性质

利用密度泛函理论和非平衡格林函数方法, 本文对小尺寸团簇Ta_n(B₃N₃H₆)_n+1 (n ≤ 4)的磁性和量子输运性质进行了系统的研究. 计算结果表明, 此类体系采用三明治结构作为其基态并且具有较高的稳定性. 体系的磁矩随团簇尺寸的增大而线性增大. 当把Ta_n(B₃N₃H₆)_n+1团簇耦合到Au电极上时, 形成的Au-Ta_n(B₃N₃H₆)_n+1-Au体系在有限偏压下展示出了较强的自旋过滤能力, 因而可以被看做是一类新型的低维自旋过滤器.     

Density functional study of TaSin (n = 1-3, 12) clusters adsorbed to graphene surface

A plane-wave density functional theory (DFT) calculations have been performed to investigate structural and electronic properties of TaSi_n (n = 1-3, 12) clusters supported by graphene surface. The resulting adsorption structures are described and discussed in terms of stability, bonding, and electron transfer between the cluster and the graphene. The TaSi_n clusters on graphene surface favor their free-standing ground-state structures. Especially in the cases of the linear TaSi₂ and the planar TaSi₃, the graphene surface may catalyze the transition of the TaSi_n clusters from an isomer of lower dimensionality into the ground-state structure. The adsorption site and configuration of TaSi_n on graphene surface are dominated by the interaction between Ta atom and graphene. Ta atom prefers to adsorb on the hollow site of graphene, and Si atoms tend to locate on the bridge site. Further, the electron transfer is found to proceed from the cluster to the surface for n = 1 and 2, while its direction reverses as n > 2. For the case of TaSi, chemisorption is shown to prevail over physisorption as the dominant mode of surface-adsorbate interaction by charge density analysis.     

4,4′,4″-三(N-3-甲基苯基-N-苯基氨基)三苯胺掺杂MoOx作为空穴传输层对有机太阳电池性能的影响

通过采用4,4′,4″-三(N-3-甲基苯基-N-苯基氨基)三苯胺 (m-MTDATA)掺入MoO_x作为器件的空穴传输层来提高酞菁铜(CuPc)/C₆₀小分子 有机太阳电池的效率. 采用真空蒸镀的方法制备了一系列器件, 其中结构为铟锡氧化物 (ITO)/m-MTDATA:MoO_x(3:1)(30 nm)/CuPc(20 nm)/C₆₀(40 nm)/4,7-二苯 基-1,10-菲罗啉 (Bphen)(8 nm)/LiF(0.8 nm)/Al(100 nm)的器件, 在AM1.5 (100 mW/cm²)模拟太阳光的照射条件下, 开路电压V_oc=0.40 V, 短路电流J_sc=6.59 mA/cm², 填充因子为0.55, 光电转换效率达1.46%, 比没有空穴传输层的器件ITO/CuPc(20 nm)/C₆₀(40 nm)/Bphen(8 nm)/LiF(0.8 nm)/Al(100 nm) 光电转换效率提高了38%. 研究表明, 加入m-MTDATA:MoO_x(3:1)(30 nm)空穴传输层减小了有机层和ITO电极之间的接触电阻, 从而减小了整个器件的串联电阻, 提高了器件的光电转换效率.     

Transport properties and mechanism of C60 coupled to carbon nanotube electrode

By applying non-equilibrium Green's functions in combination with density-functional theory, we investigate electronic transport properties of C₆₀ coupled to carbon nanotubes and Li electrodes. The results show that electronic transport properties of CNT-C₆₀-CNT and Li-C₆₀-Li systems are completely different. Nonlinear I-V characteristic, varistor-type behavior and negative differential resistance (NDR) phenomenon are observed when electrodes are carbon nanotubes. We discuss the mechanism of I-V characteristics of CNT-C₆₀-CNT systems in details. Our results suggest conductance, energy level of Frontier molecular orbitals, energy gap between HOMO and LUMO, the coupling between molecular orbitals and electrodes are all playing critical roles in electronic transport properties.     

Modulation structure in the STM images of the non-metallic misfit-layer compound (PbS)1.12VS2

This paper presents the scanning tunneling microscopy (STM) results of the misfit-layer compound (PbS)_1.12VS₂, which is constructed of alternately stacking of PbS (Q) and VS₂ (H) layers. Temperature dependent resistivity measurements show a semiconducting behavior with small activation energies. Unlike the metallic 1Q/1H type of compounds we have succeeded to take both the STM images of a Q layer and a H layer, because electron tunneling from the underlying H layer is suppressed when intermediate positive bias voltage (V_b) is applied to a tip. At V_b = 0.15 V the image shows pseudo-tetragonal arrays of bright spots, although it is obscure with decreasing bias voltage and disappears at less than 10 mV. A modulation structure is found on the H layer of a stepped surface on which surface atoms are undulated in a period being twice the V-V interatomic distance in the [1 0]_H or the [1 1]_H direction.     

宏观长Ag2S纳米线簇的制备及其温度电导特性和光电导特性

以固态离子学方法制备的宏观长银(Ag)纳米线簇为基础,采用气-固反应法制备出宏观长硫化银(Ag₂S)纳米线簇.利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能量色散谱(EDS)和X射线光电子能谱(XPS)等手段对样品形貌和成分进行表征.将厘米长的Ag₂S纳米线簇两端涂敷金胶作为电极,并与外电路连接.在不同温度或采用不同波长的光束辐照下,测试了样品的输运性质.无光照时,在144—380 K的温度范围内,样品的电导随温度上升而非线性增大.室温下,Ag关键词： 硫化银纳米线 温度电导 光电导     

The electrical properties of dielectric stacks of SiO2 and Al2O3 prepared by atomic layer deposition method

We produced dielectric stacks composed of ALD SiO₂ and ALD Al₂O₃, such as SiO₂/Al₂O₃, Al₂O₃/SiO₂, and SiO₂/Al₂O₃/SiO₂, and measured the leakage currents through the stacks in comparison with those of the single oxide layers. SiO₂/Al₂O₃ shows lowest leakage current for negative bias region below 6.4 V, and Al₂O₃/SiO₂ showed highest current under negative biases below 4.5 V. Two distinct electron conduction regimes are observed for Al₂O₃ and SiO₂/Al₂O₃. Poole-Frenkel emission is dominant at the high-voltage regime for both dielectrics, whereas the direct tunneling through the dielectric is dominant at the low-voltage regime. The calculated transition voltage between two regimes for SiO₂ (6.5 nm)/Al₂O₃ (12.6 nm) is −6.4 V, which agrees well with the experimental observation (−6.1 V). For the same EOT of entire dielectric stack, the transition voltage between two regimes decreases with thinner SiO₂ layer.     

Geometrical,electronic, and magnetic properties of Au n V (n = 1–8) clusters: A density functional study

The geometrical, electronic, and magnetic properties of small Au _n V (n?=?1–8) clusters have been investigated using density functional theory at the PW91 level. An extensive structural search indicates that the V atom in low-energy Au _n V isomers tends to occupy the most highly coordinated position and the ground-state configuration of Au _n V clusters favors a planar structure. The substitution of a V atom for an Au atom in the Au _{n +1} cluster transforms the structure of the host cluster. Maximum peaks are observed for the ground-state Au _n V clusters at n?=?2 and 4 for the size dependence of the second-order energy differences, implying that the Au₂V and Au₄V clusters possess relatively higher stability. The energy gap of the Au₃V cluster is the largest of all the clusters. This may be ascribed to its highly symmetrical geometry and closed eight-electron shell. For ground-state clusters with the same spin multiplicity, as the clusters size increases, the vertical ionization potential decreases and the electron affinity increases. Magnetism calculations for the most stable Au _n V clusters demonstrate that the V atom enhances the magnetic moment of the host clusters and carries most of the total magnetic moment.     

Au电极连接富勒烯C32分子的电子结构与传输特性

采用基于密度泛函理论(DFT)和非平衡格林函数(NEGF)的第一性原理方法对富勒烯C₃₂分子及在C₃₂分子的距离最远的两个碳原子处连接Au(1,1,1)电极的分子器件进行了电子结构和电子输运性质的研究.考虑到中间分子与Au电极间距离变化的情况,通过计算得出了在不同距离下分子器件的电子传输谱和I-V特性,分析了各器件的电子结构和电子输运特性产生的原因,并分析了电极与中间分子的连接距离及门电压对分子器件电子输运的影响.得出了电极与所连接的中间分子之