C60在Ag(111)表面的STM图像理论模拟

本文利用离散变分和局域密度泛函（ＤＶ－ＬＤＦ）方法,通过计算Ｃ６０／Ａｇ（１１１）的电荷密度分布图,即模拟出该体系的ＳＴＭ图像,并详细地研究了体系的电子结构,结果表明,该体系中有２．３２ｅ自金属表面Ａｇ原子向Ｃ６０转移。外电场的极性对图像影响委 正偏压情形,ＬＵＭＯ电荷密度分布图为三个五边形围成则呈三叶状,反映的是体系中吸附分子的对称性,且隧道电流主要来自单键。而ＨＯＭＯ电荷密度分布图具有三重对称     

单分子吸附在Cu(100)表面上的振动谱及其STM图像模拟

本文利用第一性原理方法对乙炔（C2H2），苯（C6H6）和吡啶（C5H5N）及其离解物（CCH，C6H4和C5H4N等）吸附在Cu(100）表面时C－H伸缩振动频率进行了理论计算，同时还计算了H被D替代时的C－D伸缩振动频率，理论计算结果与STM－IETS给出的测量值相当吻合，基于Tersoff-Hamann理论模型，本文还模拟出这些小分子吸附在Cu(100)表面的STM图像，与实验图像的主要特征吻合。     

Ag3PO4(111)清洁面的原子弛豫对其体系能量及电子结构的影响

采用基于密度泛函理论的第一性原理GGA+U方法,研究了Ag3PO4(111)面的原子弛豫对其体系能量及电子结构的影响.发现Ag3PO4(111)面原子弛豫后,表面两个三配位的Ag原子均向里移动超过0.06 nm,而表面次层的O原子则均向外移动0.004 nm,导致弛豫后暴露在最表面的是O原子.而且弛豫使表面原子的核外电荷向表面内部发生了一定程度转移,表面键的杂化作用使共价左右增强,表面键长缩短.计算出的能带结构和态密度显示出原子弛豫窄化了价带宽度0.15 eV,增加了带隙宽度0.26 eV.同时未弛豫结构中存在于价带顶和导带底的两个表面峰在弛豫后完全消失,弛豫使Ag3PO4表面从金属特征向半导体特征转变.     

C_(90)分子单层膜在Au(111)表面的STM研究

在超高真空中使用热蒸发方法,在Au(111)表面上制备了C90分子的分子单层膜,并利用超高真空低温扫描隧道显微镜在120 K温度下对其结构进行研究。观察到C90分子在Au(111)表面上先是沿着台阶边缘生长,分子铺满一层后,会在薄膜上形成岛状结构。本文对岛状结构进行了原位高分辨表征,观察到C90分子在正偏压和负偏压下的几种不同形貌,并给出了各种形貌所对应的C90分子构型。     

C90分子单层膜在Au(111)表面的STM研究

在超高真空中使用热蒸发方法,在Au(111)表面上制备了C90分子的分子单层膜,并利用超高真空低温扫描隧道显微镜在120 K温度下对其结构进行研究.观察到C90分子在Au(111)表面上先是沿着台阶边缘生长,分子铺满一层后,会在薄膜上形成岛状结构.本文对岛状结构进行了原位高分辨表征,观察到C90分子在正偏压和负偏压下的...     

关于Ni（100）面上C复盖的LEED和STM研究

本文叙述了Ｃ／Ｎｉ（１００）系统的ＬＥＥＤ和ＳＴＭ的研究结果，并讨论了该系统的表面结构模型。     

Investigating local (photo-)current and structure of ZnPc:C60 bulk-heterojunctions

The performance of organic solar cells strongly depends on the nanoscale structure of the used mixed absorber layer. Utilizing photoconductive and conductive atomic force microscopy (pcAFM and cAFM), as well as transmission X-ray microscopy (TXM), we investigate the influence of different substrate temperatures T_sub on the thin-film structure and local photocurrent in bulk-heterojunctions (BHJs) of vacuum deposited zinc phthalocyanine (ZnPc) and Buckminsterfullerene (C₆₀) mixed absorber layers. In this paper, we present topography maps, photocurrent maps under short-circuit current conditions, dark-current maps, and TXM images with high lateral resolution down to 25 nm. We observe a strong influence of the substrate temperatures during deposition T_sub on the nanoscopical segregation of the two components in the BHJ. This segregation leads to a spatial extension of the dark-current and a reduced short-circuit current at higher substrate deposition temperatures T_sub.     

Dark current and photovoltage models on the formation of depletion region in C60/NPB organic heterojunctions

We establish quantitative models on the formation of depletion regions in organic photodiodes (OPD) based on fullerene/N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (C₆₀/NPB) heterojunctions. The models describe the relation of dark current and open-circuit voltage to the deposited thickness of C₆₀ or NPB. Interfacial electronic structures, such as built-in potential, the charge density, the minimized thicknesses of completely developed depletion regions and the energy level bending on each side of the heterojunction were derived from the fitting model. Also, we observed a shift of depletion region from NPB to C₆₀ due to the relative change of charge density under illumination. The device performance proved the reasonability of the models. This paper provides a universally applicable method to probe the interfacial information of organic semiconductors.     

Si(111)表面电子结构

本文利用自洽LMTO-ASA方法研究了晶体Si及Si(111)表面的几种模型的电子结构,给出了在slab模型各不同结构下的态密度和分波态密度,以及各不等价原子态密度和分波态密度,该结果与其它理论计算和实验结果相吻合     

Strain tunable band structure of a new 2D carbon allotrope C568

Recently, C₅₆₈ has emerged as a new carbon allotrope, which shows semiconducting properties with a band gap around 1 eV and has attracted much attention. In this work, the external strain effects on the electronic properties of C₅₆₈ have been studied theoretically through first-principle calculations. The numerical results show that while in-plane uniaxial and biaxial strains both reduces the band gap of C₅₆₈ in case of tensile strain, their effects are quite different in the case of compressive strain. With increasing compressive uniaxial strain, the band gap of C₅₆₈ first increases, and then dramatically decreases. In contrast, the application of compressive biaxial strain up to –10% only leads to a slight increase of band gap. Moreover, an indirect-to-direct gap transition can be realized under both types of compressive strain. The results also show that the optical anisotropy of C₅₆₈ can be induced under uniaxial strain, while biaxial strain does not cause such an effect. These results indicate good strain tunability of the band structure of C₅₆₈, which could be helpful for the design and optimization of C₅₆₈-based nanodevices.     

Sn在Cu(111)上欠电位沉积的现场STM研究

本文用现场扫描隧道显微镜（in-situ STM)研究Sn在Cu(111）上的欠电位沉积（underpotential deposition UPD)过程,实验结果表明：Sn原子在Cu(111)表面上的UPD首先在晶面的边缘处发生,随后向晶面的其余地方发展并取代吸附在表面的SO4^2-,这一过程伴随着显著的台阶轮廓的变化,在Sn的UPD层溶出过程中,台阶边缘形状发生了更剧烈的变化。并且观察到凹洞的出现,表明Sn与Cu (111)基底形成了表面合金。     

A comparison of two air-stable molecular n-dopants for C60

We compare two air-stable n-dopants for the fullerene C₆₀: AOB and DMBI-POH. Conductivity and Seebeck coefficient measurements were performed at various doping concentrations and the thermal activation of the conductivity was determined. A superlinear increase of conductivity upon doping was found for DMBI-POH doped C₆₀ reaching a maximum conductivity of 5.3 S/cm. In contrast to this, a linear rise of conductivity and an exponential thermal activation of mobility was observed for C₆₀ doped by AOB. This suggests a different doping mechanism for the two compounds.     

C_(60),M@C_(60)电子传输特性研究

采用扩展的Hückel方法与格林函数方法,分析了双Au电极作用下,C60,M@C60(M=Si,Ge)富勒烯分子的电子结构与导电性,并对三种富勒烯分子的电子结构与电子输运特性进行了对比。研究结果表明,三种富勒烯分子与A u电极“接触”后,其最高占据分子轨道与最低未占据分子轨道间的能隙减小,它们与A u电极之间的结合既有共价键的成分,又有离子键的成分;三种富勒烯分子的电子输运性能依次具有Ge@C60>Si@C60>C60的顺序。     

Zn掺杂和Sn空位对p型SnO2电子结构和光学性能的影响

用第一性原理计算了本征SnO2、Zn掺杂SnO2、带Sn 空位(VSn)的SnO2和Zn-VSn共掺杂 SnO2的电子结构和光学性能。结果表明,Zn 原子替位SnO2中的Sn原子后费米能级进入价带,价带顶的空能态由Zn 3d和O 2p态组成,Zn掺杂SnO2显示p型半导体性能。 带Sn空位的Zn掺杂SnO2的相对空穴数量较Zn掺杂SnO2的相对空穴数量有明显增加,Sn空位有助于增加Zn掺杂SnO2的p型导电性。Zn掺杂SnO2在可见光区域有明显的光吸收,带Sn空位的Zn掺杂SnO2的光吸收较Zn掺杂SnO2明显增强,吸收光谱发生蓝移。     

(InSb)m/(HgTe)n短周期超晶格的电子结构

Theelectronicstructureof（InSb）m/（HgTe）nshortperiodsuperlatticesgrownalongthe（001）directionis studiedtheoreticallyusingnorm-conservingpseudo-potentialstogetherwiththelocal-densityapproximationforthe exchange-correlationpotential.Thebandstructuredependsonthevalueofmandn,thenumberofmono-layersand on the ordering of atoms at the InSb/HgTe interface in one unit cell. Our calculation indicates that the superlattice can be a semiconductor having a band gap between the occupied and unoccupied bands, or a metal with no band gap at the Fermi energy. According to the further calculation of total charge density between（InSb）m/（HgTe）nwith different structures, a clearly different behavior happens when the structure changes from a system with a gap and a system without a gap.     

Electronic structures and optical properties of Nb-doped SrTiO3 from first principles

The n-type Nb-doped SrTiO₃ with different doping concentrations were studied by first principles calculations. The effects of Nb concentration on the formation enthalpy, electronic structure and optical property were investigated. Results show that Nb preferentially enters the Ti site in SrTiO₃, which is in good agreement with the experimental observation. The Fermi level of Nb-doped SrTiO₃ moves into the bottom of the conduction band, and the system becomes an n-type semiconductor. The effect of Nb-doping concentration on the conductivity was discussed from the microscopic point of view. Furthermore, the 1.11 at% Nb-doped SrTiO₃ shows strong absorption in the visible light and becomes a very useful material for photo-catalytic activity. The 1.67 at% and 2.5 at% Nb-doped models will be potential transparent conductive materials.     

二氧化钛掺杂系统的电子结构和光学性质的研究

采用总能量平面波赝势方法研究了Sc掺杂、含氧空位、氧空位与Sc掺杂共存时的锐钛矿TiO2系统的电子结构和光学性质。结果表明,Sc掺杂对系统的主要贡献在价带区,在可见光区有明显的光吸收;氧空位可以使系统发生莫特相变,系统在可见光区也有较强的吸收;氧空位与Sc掺杂共存时系统在可见光区的吸收相干加强。     

Stability and Electronic Characteristics of Epitaxial Silicene Multilayers on Ag(111)

In this study, the stability and electronic characteristics of epitaxial silicene bilayers and multilayers on the Ag(111) surface are investigated through synchrotron‐based soft X‐ray emission and absorption spectroscopy and first‐principles, full‐potential density functional theory simulations. The calculations predict a novel tristable AA‐stacked bilayer structure that can explain the (√3 × √3)R30° honeycomb topography commonly observed through scanning tunneling microscopy and noncontact atomic force microscopy. It is reported that the electronic structure of this epitaxial bilayer is similar to those of epitaxial monolayers on Ag(111), namely, metallic and showing significant interaction with the underlying substrate. However, the soft X‐ray spectroscopy experiments suggest that during multilayer growth a majority of the epitaxial silicon reverts to a bulk‐like state, a result that has significant implications toward the existence of large‐area epitaxial silicene multilayers.     

锐钛矿TiO2(101)面电子性质和光学性质的第一性原理研究

The TiO₂（101） surface was studied using the plane-wave ultrasoft pseudopotential method based on the density functional theory,with emphasis on the structure,surface energy,band structure,density of states, and charge population.The anatase TiO₂（101） crystal surface structure,whose outermost and second layers were terminated by twofold coordinated oxygen atoms and fivefold coordinated titanium atoms,was found to be much more stable.The surface energy of the 18-layer atoms model was 0.580 J/m2.The surface electronic structure was similar to that of the bulk and no surface state.Compared with the bulk structure,the band gap increased 0.36 eV, the Ti5c-02c bond lengths reduced 0.171（?） after relaxation,and the charges of the surface were transferred to the body.Analysis of the optical properties of the TiO₂（101） surface showed that it did not absorb in the low-energy region.An absorption edge in the ultraviolet region corresponding to the energy of 3.06 eV was found.     

半金属表面上酞菁锰分子的转动态研究

利用低温STM研究了半金属Bi(111)表面上单个酞菁锰分子的转动态。通过高分辨STM图发现,在液氮温度(77K)下单个酞菁锰分子呈六角形。利用STM操纵技术实现了对单个酞菁锰分子的制动,并通过对单分子的高低起伏和吸附构型分析,确定分子在Bi(111)表面做非连续的中心转动。这种单分子转动是三种相对稳定的吸附构型交替变化的结果。结合I-t谱技术,进一步验证了这三种分子吸附构型的存在;并利用近似统计分析方法得到三种吸附构型各自出现的概率以及其相对能量。