Biomedical subjects

Kurt Stokbro

Publications and source records attributed to Kurt Stokbro.

4 recordsLinked to original sources

PubMed2004

Scanning tunneling microscopy of self-assembled phenylene ethynylene oligomers on Au(111) substrates.

In this paper, we report the self-assembly, electrical characterization, and surface modification of dithiolated phenylene-ethynylene oligomer monolayers on a Au(111) surface. The self-assembly was accomplished by thiol bonding the molecules from solution to a Au(111) surface. We have confirmed the formation of self-assembled monolayers by scanning tunneling microscopy (STM) and optical ellipsometry, and have studied the kinetics of film growth. We suggest that self-assembled phenylene ethynylene oligomers on Au(111) surfaces grow as thiols rather than as thiolates. Using low-temperature STM, we collected local current-voltage spectra showing negative differential resistance at 6 K.

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PubMed2003

Do Aviram-Ratner diodes rectify?

We present state-of-the-art first principles calculations for the IV characteristics of a donor-insulator-acceptor (DsigmaA) type molecular diode anchored with thiolate bonds to two gold electrodes. We find very poor diode characteristics of the device, and the origin of this is analyzed in terms of the bias-dependent electronic structure. At zero bias, the highest occupied molecular orbital (HOMO) is confined to the D part, and the lowest unoccupied molecular orbital (LUMO) is confined to the A part, while at 3.8 V the two states align, and this gives rise to an increasing current. The latter is a potential mechanism for rectification and may in some cases lead to favorable diode characteristics. We identify the origin of the vanishing rectification for the investigated molecule, and on the basis of this we suggest parameters which are important for successful chemical engineering of DsigmaA rectifiers.

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PubMed2003

TranSIESTA: a spice for molecular electronics.

Our recently developed method, TranSIESTA, enables modelling of molecular electronic devices under operation conditions. The method is based on density functional theory, and calculates the self-consistent electronic structure of a nanostructure coupled to three-dimensional electrodes with different electrochemical potentials. It uses a full atomistic ab initio description of both the electrodes and the nanoscale device. The calculations reveal information about the scattering states, transmission coefficients, electron current, and non-equilibrium forces in the systems. In this paper we use the method to investigate the electrical properties of three ring phenyl-ethynylene oligomers (OPE). We present results for the electrical effect of side groups and molecular conformations of the molecules. The calculations indicate that molecular switching and negative differential conductance (NDC) are related to rotations of the middle phenyl ring.

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PubMed2002

Theory of rectification in tour wires: the role of electrode coupling.

We report first-principles studies of electronic transport and rectification in molecular wires attached to gold electrodes. Our ab initio calculation gives an accurate description of the voltage drop as well as the broadening and alignment of the molecular levels in the metal-molecule-metal complex. We find that the operation range and rectification in such strongly chemisorbed molecules is limited by the width of the transmission resonances and their proximity to the Fermi level.

Journal Article↗