Molecular electronics based on self-assembled monolayers
D. Vuillaume
备注：
To appear in "Oxford handbook of nanoscience and nanotechnology. Frontiers and advances", eds. A. Narlikar & Y. Fu (Oxford university press, 2008), vol. III, chap. 9
发表信息：
"The Oxford handbook of nanoscience and nanotechnology", eds. A.V. Narlikar & Y.Y. Fu (Oxford university press, 2010), vol. III, chap. 9, pp. 312-3342
Since the first measurement of electron tunneling through an organic monolayer in 1971,(Mann and Kuhn, 1971) and the gedanken experiment of a molecular current rectifying diode in 1974,(Aviram and Ratner, 1974) molecular-scale electronics have attracted a growing interest, both for basic science at the nanoscale and for possible applications in nano-electronics. In the first case, molecules are quantum object by nature and their properties can be tailored by chemistry opening avenues for new experiments. In the second case, molecule-based devices are envisioned to complement silicon devices by providing new functions or already existing functions at a simpler process level and at a lower cost by virtue of their self-organization capabilities, moreover, they are not bound to von Neuman architecture and this may open the way to other architectural paradigms. After a brief overview of the nanofabrication of molecular devices, we review in this chapter, the electronic properties of several basic devices, from simple molecules such as molecular tunnel junctions and molecular wires, to more complex ones such as molecular rectifying diodes, molecular switches and memories.
Nanostructured films obtained by the assembling of preformed atomic clusters are of strategic importance for a wide variety of applications. The deposition of clusters produced in the gas phase onto a substrate offers the possibility to control and engineer the structural and functional properties of the cluster-assembled films. To date the microscopic mechanisms underlying the growth and structuring of cluster-assembled films are poorly understood, and in particular the transition from the sub-monolayer to the thin film regime is experimentally unexplored. Here we report the systematic charac…
We report the formation of self-assembled monolayers of a molecular photoswitch (azobenzene-bithiophene derivative, AzBT) on cobalt via a thiol covalent bond. We study the electrical properties of the molecular junctions formed with the tip of a conductive atomic force microscope under ultra-high vacuum. The statistical analysis of the current-voltage curves shows two distinct states of the molecule conductance, suggesting the coexistence of both the trans and cis azobenzene isomers on the surface. The cis isomer population (trans isomer) increases (decreases) upon UV light irradiation. The si…
We report how the electron transport through a solid-state metal/Gly-Gly-His tripeptide (GGH) monolayer/metal junction and the metal/GGH work function are modified by the GGH complexation with Cu2+ ions. Conducting AFM is used to measure the current-voltage histograms. The work function is characterized by combining macroscopic Kelvin probe and Kelvin probe force microscopy at the nanoscale. We observe that the Cu2+ ions complexation with the GGH monolayer is highly dependent on the molecular surface density and results in opposite trends. In the case of a high density monolayer the conformati…
Two new photo-switchable terphenylthiazoles molecules are synthesized and self-assembled as monolayers on Au and on ferromagnetic Co electrodes. The electron transport properties probed by conductive atomic force microscopy in ultra-high vacuum reveal a conductance of the light-induced closed (c) form larger than for the open (o) form. We report an unprecedented conductance ratio up to 380 between the closed and open forms on Co for the molecule with the anchoring group (thiol) on the side of the two N atoms of the thiazole unit. This result is rationalized by Density Functional Theory (DFT) c…
We report on the phosphonic acid route for the grafting of functional molecules, optical switch (dithienylethene diphosphonic acid, DDA), on La0.7Sr0.3MnO3 (LSMO). Compact self-assembled monolayers (SAMs) of DDA are formed on LSMO as studied by topographic atomic force microscopy (AFM), ellipsometry, water contact angle and X-ray photoemission spectroscopy (XPS). The conducting AFM measurements show that the electrical conductance of LSMO/DDA is about 3 decades below that of the bare LSMO substrate. Moreover, the presence of the DDA SAM suppresses the known conductance switching of the LSMO su…
Self-assembled monolayer molecule dynamics are perturbed by surface- and surrounding monolayer-derived geometrical confinement
薄膜附着的表面和周围的单层导致被询问分子的几何限制;我们研究了Au上SC $_{18}H_{37}$单层中SC $_{18}H_{37}$的基本情况[111]。正常模式分析用于获得振动，并且这些使用模式特征指标进行分析，这些指标可以量化：一个元素在模式中的活跃程度;模式的总体方向;以及哪些化学坐标是相关的。我们研究了4种可能的包装结构。我们发现，更稳定的结构，更少的扰动的表面和周围的单层支持。表面扰动模式低于100 cm $^{-1}$，具有较高的全局、碳、硫、纵向和扭转特征，表明晶胞骨架运动，通常具有平行于表面的增加的S运动和增加的末端甲基运动。通过这种技术确定的模式显示出实验振动（有和没有表面）之间的差异是那些没有确定的两倍。周围的单层对单分子动力学的影响比表面大，包括稳定分子足以使12个高能量模式将$\approx$ 425 cm $^{-1}$的能量降低到低于$k_B T$，使它们在室温下被填充。这些模式具有较高的局域性和高H值特性，并受到SAM结构的高度调制。这项工作显示了新的方法来分析振动，并证明了至关重要的需要，包括几何约束效应SAM的研究。
Effects of charged defects on the electronic and optical properties of self-assembled quantum dots
研究了点电荷缺陷对应变In $_{0.6}$ Ga $_{0.4}$ As/GaAs和无应变GaAs/Al $_{0.3}$ Ga $_{0.7}$ As量子点的单粒子电子结构、发射能量、精细结构分裂和激子跃迁振子强度的影响.我们发现，带电缺陷显着修改单粒子的电子结构和激子光谱在应变和无应变的结构。然而，激子精细结构分裂，偏振各向异性和偏振方向在应变量子点几乎不受影响，而观察到显着的变化为无应变量子点。
Electronic and Optical Properties of Self-Assembled Quantum Wires
我们研究了自组装量子线的能带和光学性质。特别地，通过有效键轨道模型（EBOM），考虑了价带各向异性和能带混合的影响，从理论上研究了应变多量子线（QWR）的能带结构和光学矩阵元。结果表明，应变导致载流子的进一步限制和各向异性的增强。利用EBOM和价力场模型，系统地研究了微应变对Ga $_{1-x}$ In $_x$ As短周期应变诱导横向有序超晶格自组装量子线的电学和光学性质的影响.模型考虑了原子水平上的价带各向异性、能带混合以及局域应变分布的影响，给出了模型中不同结构的综合集合.最后，利用我们的包络函数模型研究了SILO量子线的激子吸收谱。
Benzo-bis(imidazole) self-assembled monolayers molecular junctions in meta or para conformation: effects of protonation on the electrical and thermal conductances
Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), CNRS（马赛跨学科纳米科学中心）
Nanoscience offers a unique opportunity to design modern materials from the bottom up, via low-cost, solution processed assembly of nanoscale building blocks. These systems promise electronic band structure engineering using not only the nanoscale structural modulation, but also the mesoscale spatial patterning, although experimental realization of the latter has been challenging. Here we design and fabricate a new type of artificial solid by stacking graphene on a self-assembled, nearly periodic array of nanospheres, and experimentally observe superlattice miniband effects. We find conductanc…
To quantify charge transport through molecular junctions fabricated using the conducting probe atomic force microscopy (CP-AFM) platform, information on the number of molecules $N$ per junction is absolutely necessary. $N$ can be currently obtained only via contact mechanics, and the Young's modulus $E$ of the self-assembled monolayer (SAM) utilized in the key quantity for this approach. The experimental determination of $E$ for SAMs of CP-AFM junctions fabricated using oligophenylene dithiols (OPDn, $1 \leq n \leq 4$) and gold electrodes turned out to be too challenging. Recent measurements (…
We report the first principle theory-based study of stability, electronic structure and optical properties of cluster assembled materials in various 1D, 2D and 3D nanostructures using a cage-like Cd9Te9 cluster as the super-atom. The bulk 3D self-assemblies form in 2D stacked structures for different cubic lattices. The face centered stacking is the most stable as compared to the simple cubic, body centered and zinc blende type stackings. The 2D stacks are formed as cluster assembled monolayers and the monolayer derived from the face centered structure is most stable. Further, the cluster chai…
Some electronic and optical properties of self-assembled quantum dots: asymmetries in a lens domain
具有透镜畴的自组装量子点具有旋转对称性，但当电子垂直于其圆形基底运动时，其本质上是不对称的，{ \it i. e.}沿着旋转轴。为了表征这种不对称性，沿旋转轴的正或负方向施加外部电场。我们报告了不同的斯塔克位移出现在光谱中作为一个函数的场强度为不同的透镜域。结果表明，对于一个平坦的透镜域的不对称性的影响减少，但即使是非常平坦的透镜，他们不能近似的柱面域。最后，我们研究了它的介电常数和电吸收等光学性质。能谱的特征显示了这些量。强调了只要调节特定能级跃迁的大小和方向场，就应考虑适当的透镜域的重要性。
The OH-terminated self-assembled monolayers, as protein-resistant surfaces, have significant potential in biocompatible implant devices, which can avoid or reduce adverse reactions caused by protein adhesion to biomaterial surfaces, such as thrombosis, immune response and inflammation. Here, molecular dynamics simulations were performed to evaluate the degree of protein adsorption on the self-assembled monolayer terminated with two hydrophilic OH groups ((OH)2-SAM) at the packing densities (Σ) of 4.5 nm-2 and 6.5 nm-2, respectively. The results show that the (OH)2-SAM itself can significantly …
Using the continuum model, we investigate theoretically contribution of the low-energy electronic excitations to the Raman spectrum of superconducting monolayer graphene. We consider superconducting phases characterised by an isotropic order parameter in a single valley and find a Raman peak at a shift set by the size of the superconducting gap. The height of this peak is proportional to the square root of the gap and the third power of the Fermi level, and we estimate its quantum efficiency as $I\sim10^{-14}$.
Migration of gold atoms into a thiol-bonded molecular self-assembled monolayer, forming a cluster exhibiting a Coulomb staircase
Cavendish Laboratory, University of Cambridge（剑桥大学卡文迪许实验室）；Department of Chemistry, Korea University（韩国大学化学系）；Physics Department, Lancaster University（兰卡斯特大学物理系）
The interaction of DNA nucleobases with monolayer GaSe has been studied with in DFT framework using vdW functional. We found that nucleobases are physisorbed on the GaSe monolayer. The order of binding energy per atom is C > T > G > A. The room temperature recovery time estimated to be maximum of 113.88 micro sec. for T+GaSe indicting reusability of the GaSe based devices. The modulation in the electronic structures of GaSe has been clearly captured within the simulated STM measurements. We also demonstrate quantum capacitance as a key parameter for sensing applications. Furthermore, in optica…
We investigate the electronic transport property of lateral heterojunctions of semiconducting and metallic transition-metal dichalcogenide monolayers, MoSe$_2$ and NbSe$_2$, respectively. We calculate the electronic transmission probability by using a multi-orbital tight-binding model based on the first-principles band structure. The transmission probability depends on the spin and valley degrees of freedom. This dependence qualitatively changes by the interface structure. The heterostructure with a zig-zag interface preserves the spin and the valley of electron in the transmission process. On…
Strain engineering applied to carbon monosulphide monolayers allows to control the bandgap, controlling electronic and thermoelectric responses. Herein, we study the semiconductor-metal phase transition of this layered material driven by strain control on the basis of first-principles calculations. We consider uniaxial and biaxial tensile strain and we find a highly anisotropic electronic and thermoelectonic responses depending on the direction of the applied strain. Our results indicate that strain-induced response could be an effective method to control the electronic response and the thermo…
We report an easy and broadly applicable method for the controlled self-assembly of atomically precise Au32(nBu3P)12Cl8 nanoclusters into micro-crystals. This enables the determination of emergent optoelectronic properties resulting from long-range order in such assemblies. Compared to the same nanoclusters in glassy, polycrystalline ensembles, we find a 100-fold increase in the electric conductivity and charge carrier mobility as well as additional optical transitions. We show that these effects are due to a vanishing energetic disorder and a drastically reduced activation energy to charge tr…
It is highly desirable to search for promising two-dimensional (2D) monolayer materials for deep insight of 2D materials and applications. We use first-principles method to investigate tetragonal perovskite oxide monolayers as 2D materials. We find four stable 2D monolayer materials from SrTiO$_3$, LaAlO$_3$, KTaO$_3$, and BaFeO$_3$, denoting them as STO-ML, LAO-ML, KTO-ML, and BFO-ML. Our further study shows that through overcoming dangling bonds the first three monolayers are 2D wide-gap semiconducotors, and BFO-ML is a 2D isotropic Heisenberg ferromagnetic metal. There is a large electrosta…
First-principle calculations of phononic, electronic and optical properties of monolayer arsenene and antimonene allotropes
最近，在三维拓扑绝缘体Bi $_2$ Te $_3$和Sb $_2$ Te $_3$上成功地生长了一种稳定的单层锑，其具有弯曲的蜂窝结构，称为锑烯，显示出半导体性质。通过第一性原理计算，系统地研究了单层砷烯/锑烯同素异形体$α-$和$β-$的声子、电子和光学性质.通过考虑声子色散，我们研究了这四种材料的动力学稳定性。计算结果表明，单层$α-$ As/Sb具有直接带隙，单层$β-$ As/Sb具有间接带隙，$α-$ Sb具有明显的吸收，可作为一种宽饱和吸收体.
The recently synthesized two-dimensional electride Gd$_2$C was proposed to be a ferromagnetic metal that possesses multiple pairs of Weyl points and may display a large anomalous Hall conductivity [Liu \textit{et al.}, Phys. Rev. Lett. \textbf{125}, 187203 (2020)]. In view of its layered structure, here we carry out first-principles studies on the magnetic and electronic properties of Gd$_2$C in the ultrathin monolayer limit. We find that monolayer Gd$_2$C remains ferromagnetic like the bulk form and the hydrogenation can effectively tune its magnetism and electronic structure. With one-sided …
2H phase (trigonal prismatic D3h) of layered two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted a lot of interests due to the superior electronic and optoelectronic properties. However, flexible electronic devices and thermoelectric performances based on 2H phase have been potentially limited by the strain sensitive electronic band gap and high lattice thermal conductivity (kappa_L). Here, we predict and calculate two 1T (octahedral Oh) phase monolayer telluride materials SnTe2 and SiTe2 with soft mechanics, ultralow kappa_L and electronic properties. The calculated in…
The monolayer WSe2 is interesting and important for future application in nanoelectronics, spintronics and valleytronics devices, because it has the largest spin splitting and longest valley coherence time among all the known monolayer transition-metal dichalcogenides (TMDs). To obtain the large-area monolayer TMDs' crystal is the first step to manufacture scalable and high-performance electronic devices. In this letter, we have successfully fabricated millimeter-sized monolayer WSe2 single crystals with very high quality, based on our improved mechanical exfoliation method. With such superior…
