Transmission eigenvalue distributions in highly conductive molecular junctions

• Justin P. Bergfield,
• Joshua D. Barr and
• Charles A. Stafford

Beilstein J. Nanotechnol. 2012, 3, 40–51, doi:10.3762/bjnano.3.5

• each Pt tip, we include one s, three p and five d orbitals in our calculations, which represent the evanescent tunneling modes in free space outside the apex atom of the tip. At room temperature, the Pt density of states (DOS) ρα(E) = Σlρlα(E) is sharply peaked around the Fermi energy [26] with ρα(εF

• the quasi-atomic wavefunctions of the atomically sharp electrode are relevant. In this case we may express the elements of Γα as [6] where the sum is calculated over the evanescent tunneling modes emanating from the metal tip, labeled by their angular-momentum quantum numbers, is the local density of

• states on the apex atom of electrode α, and is the tunneling matrix element of orbitals l [25]. The constants Cl can in principle be determined by matching the evanescent tip modes to the wavefunctions within the metal tip [25]; however, we set and determine the constant C by fitting to the peak of the

When “small” terms matter: Coupled interference features in the transport properties of cross-conjugated molecules

• Gemma C. Solomon,
• Justin P. Bergfield,
• Charles A. Stafford and
• Mark A. Ratner

Beilstein J. Nanotechnol. 2011, 2, 862–871, doi:10.3762/bjnano.2.95

• to each electrode, with coupling strength γ = βS/3 = −1 eV. For this system we have: The transmission is then calculated by using the nonequilibrium Green’s function formalism assuming the wide-band limit for the density of states of the electrodes and setting where ρ is the density of states of the

• Green’s functions in the same way as the Hückel model calculations, that is simply by using the gDFTB Hamiltonian in place of the Hückel Hamiltonian. A wide-band approximation is also employed in which the density of states used to construct the self-energies is set to a value for bulk gold (1.9 eV −1

Current-induced dynamics in carbon atomic contacts

• Jing-Tao Lü,
• Tue Gunst,
• Per Hedegård and
• Mads Brandbyge

Beilstein J. Nanotechnol. 2011, 2, 814–823, doi:10.3762/bjnano.2.90

• the frequency (energy) domain. This can be expressed by using the coupling-weighted electron–hole-pair density of states, Λαβ, inside or between electrodes α,β L,R, where Λ can be expressed in terms of the electrode DOS, We have included a factor of 2 from the spin degeneracy and have explicitly

STM study on the self-assembly of oligothiophene-based organic semiconductors

• Elena Mena-Osteritz,
• Marta Urdanpilleta,
• Erwaa El-Hosseiny,
• Berndt Koslowski,
• Paul Ziemann and
• Peter Bäuerle

Beilstein J. Nanotechnol. 2011, 2, 802–808, doi:10.3762/bjnano.2.88

• , center) submolecular resolution was obtained for the oligothiophene backbones. Due to the low negative bias applied and at the limit given by the tunneling barrier of this compound, we can assume that the observed eight lobes per molecule correspond to the local density of states (LDOS) of the molecule

Effect of the environment on the electrical conductance of the single benzene-1,4-diamine molecule junction

• Shigeto Nakashima,
• Yuuta Takahashi and
• Manabu Kiguchi

Beilstein J. Nanotechnol. 2011, 2, 755–759, doi:10.3762/bjnano.2.83

• techniques. In the simple tunneling model, the transmission (T(E)) of the single-molecule junction can be represented by where t, ρ, Crk and εk are the hopping integral between the metal and molecular orbitals (MO), the local density of states (LDOS) of the metals at the Fermi level (EF), the kth MO

Towards quantitative accuracy in first-principles transport calculations: The GW method applied to alkane/gold junctions

• Mikkel Strange and
• Kristian S. Thygesen

Beilstein J. Nanotechnol. 2011, 2, 746–754, doi:10.3762/bjnano.2.82

• eV. This finding agrees well with previous studies on a broader range of small molecules [24][29][30]. In the junction, the molecular orbitals, , were obtained by diagonalizing the DFT Hamiltonian corresponding to the molecule. The projected density of states (PDOS) of such a state is then given by

Nonconservative current-induced forces: A physical interpretation

• Tchavdar N. Todorov,
• Daniel Dundas,
• Anthony T. Paxton and
• Andrew P. Horsfield

Beilstein J. Nanotechnol. 2011, 2, 727–733, doi:10.3762/bjnano.2.79

• the electronic density of states, evaluated at the Fermi level μ; Δ(Q) is the nonequilibrium part of the one-electron density matrix (that is, the difference between the steady-state current-carrying density matrix and the equilibrium density matrix); finally, (Q) is the force operator where Ĥe(Q) is

• the continuum r-representation, We also have where ν = x,y,z and j(r,R) is the electron particle-current density. Then, to lowest order in C, we obtain where D(r,μ) = D(r,r,μ) and j(r) are the local density of states at the Fermi level and the particle-current density in the absence of the point

• two form a complete orthonormal set. The left reservoir populates states l, in a grand-canonical ensemble with electrochemical potential μL (and a chosen electronic temperature); the right reservoir populates states r with electrochemical potential μR. It is convenient to define the density of states

STM visualisation of counterions and the effect of charges on self-assembled monolayers of macrocycles

• Tibor Kudernac,
• Natalia Shabelina,
• Wael Mamdouh,
• Sigurd Höger and
• Steven De Feyter

Beilstein J. Nanotechnol. 2011, 2, 674–680, doi:10.3762/bjnano.2.72

• nitrogen atoms. As STM contrast is a convolution of the physical height and the local density of states [28], the large iodides “sitting” on top of the macrocycle rim logically result in a strong STM signal. Additionally, higher polarisability of iodine, as compared to the other atoms present, can

Deconvolution of the density of states of tip and sample through constant-current tunneling spectroscopy

• Holger Pfeifer,
• Berndt Koslowski and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 607–617, doi:10.3762/bjnano.2.64

• Holger Pfeifer Berndt Koslowski Paul Ziemann Institut für Festkörperphysik, Universität Ulm, D-89069 Ulm, Germany 10.3762/bjnano.2.64 Abstract We introduce a scheme to obtain the deconvolved density of states (DOS) of the tip and sample, from scanning tunneling spectra determined in the constant

• property that can be accessed by STS is the local electronic density of states (LDOS). For that purpose, the applied tunneling bias, V, is ramped while the probe–sample separation is kept constant (commonly denoted as I–V spectroscopy) [1][3]. However, determination of the sample LDOS from such a

• transmission probability function (TPF), T(E,V,z). Assuming zero temperature, application of a bias, V, results in a tunneling current which, according to WKB, can be written as where ρS and ρT are the sample and tip density of states (DOS), respectively, and E is the energy of electrons participating in the

Terthiophene on Au(111): A scanning tunneling microscopy and spectroscopy study

• Berndt Koslowski,
• Anna Tschetschetkin,
• Norbert Maurer,
• Elena Mena-Osteritz,
• Peter Bäuerle and
• Paul Ziemann

Beilstein J. Nanotechnol. 2011, 2, 561–568, doi:10.3762/bjnano.2.60

• indicating an adsorption-induced dimensionality transition of the involved tunneling processes. Keywords: Au(111); electronic density of states; STM; STS; terthiophene; Introduction Because of their expedient properties and their diversity, oligo- and polythiophenes are among the most investigated organic

• separation of the molecules from the surface of 0.315 nm [20]. Such a considerable difference requires an explanation. Typically one would argue in STM that a change of the density of states (DOS) or the barrier height, Φ, above a molecule changes the tip–sample separation. However, the spatial distribution

• contributes perceptibly to the density of states (DOS) and, to maintain the current setpoint under feedback, the tip must be withdrawn from the surface with increasing bias in accordance with the DOS of the LUMO, thus leading to an enhanced apparent height of the 3T molecule. For the LUMO energy, a molecular

Charge transfer through single molecule contacts: How reliable are rate descriptions?

• Denis Kast,
• L. Kecke and
• J. Ankerhold

Beilstein J. Nanotechnol. 2011, 2, 416–426, doi:10.3762/bjnano.2.47

• notable difference, of course, that in this case one has a discrete density of states for both sites [20][22]. The fundamental assumption underlying the golden rule treatment is that equilibration of the phonon mode occurs much faster than charge transfer. In the last two cases this is typically

Influence of water on the properties of an Au/Mpy/Pd metal/molecule/metal junction

• Jan Kučera and
• Axel Groß

Beilstein J. Nanotechnol. 2011, 2, 384–393, doi:10.3762/bjnano.2.44

• electronic structure of these Pd atoms is considerably modified which is reflected in a reduced local density of states at the Fermi energy. At higher coverages, water can be arranged in a hexagonal ice-like bilayer structure in analogy to water on bulk metal surfaces, but with a much stronger binding which

• of the palladium monolayer with respect to bulk Pd [7][8]. For both the Mpy- and the ATP-SAM the density of states (DOS) of the Pd monolayer was found to be significantly reduced at the Fermi level with the maximum of the DOS shifted to about −1.8 eV below the Fermi energy. Two possible scenarios

• adsorption. In particular we will discuss the character of the palladium local density of states (LDOS) in the presence of water and compare the findings with experimental UPS spectra of the corresponding system. Results and Discussion Before addressing the water adsorption on the Au/Mpy/Pd junction, we will

Extended X-ray absorption fine structure of bimetallic nanoparticles

• Carolin Antoniak

Beilstein J. Nanotechnol. 2011, 2, 237–251, doi:10.3762/bjnano.2.28

• structure (XANES) The XANES includes information about the density of states (DOS) of the absorbing atoms. More precisely, the XANES is connected to the unoccupied electronic DOS of the excited atom in the presence of a core-hole. In this section, the description of the XANES by the standard one-electron

Defects in oxide surfaces studied by atomic force and scanning tunneling microscopy

• Thomas König,
• Georg H. Simon,
• Lars Heinke,
• Leonid Lichtenstein and
• Markus Heyde

Beilstein J. Nanotechnol. 2011, 2, 1–14, doi:10.3762/bjnano.2.1

• microscopic tip is within ±2 meV. All defect types analyzed show a characteristic fingerprint due to different charge states. The measurements based on NC-AFM are supported by complementary STS. For all defects the local density of states (LDOS) has been detected. The tunneling spectra measurements have been

On the reticular construction concept of covalent organic frameworks

• Binit Lukose,
• Agnieszka Kuc,
• Johannes Frenzel and
• Thomas Heine

Beilstein J. Nanotechnol. 2010, 1, 60–70, doi:10.3762/bjnano.1.8

• distances. Generally, AB, serrated and inclined stacked COFs have band gaps comparable to, or larger than, that of their AA stacked analogues. We have calculated the electronic total density of states (TDOS) and the individual atomic contributions (partial density of states, PDOS). The energy state

• electronic properties. We have studied each COF in high-symmetry AA and AB as well as low-symmetry inclined and serrated stacking forms. The optimized COF structures exhibit different interlayer separations and band gaps in different kinds of layer stackings; however, the density of states of a single layer

• second code, which can perform calculations using k-points, was used to calculate the electronic properties (band structure and density of states). Band gaps have been calculated as an additional stability indicator. While these quantities are typically strongly underestimated in standard LDA- and GGA