2,503 research outputs found
Charge Transport in Single Au|Alkanedithiol|Au Junctions: Coordination Geometries and Conformational Degrees of Freedom
Recent STM molecular break-junction experiments have revealed multiple series
of peaks in the conductance histograms of alkanedithiols. To resolve a current
controversy, we present here an in-depth study of charge transport properties
of Au|alkanedithiol|Au junctions. Conductance histograms extracted from our STM
measurements unambiguously confirm features showing more than one set of
junction configurations. Based on quantum chemistry calculations, we propose
that certain combinations of different sulfur-gold couplings and trans/gauche
conformations act as the driving agents. The present study may have
implications for experimental methodology: whenever conductances of different
junction conformations are not statistically independent, the conductance
histogram technique can exhibit a single series only, even though a much larger
abundance of microscopic realizations exists.Comment: 19 pages, 9 figures, 1 table; published versio
Reflection of plane waves by rough surfaces in the sense of Born approximation
The topic of the present paper is the reflection of electromagnetic plane waves by rough surfaces, i.e., by smooth and bounded perturbations of planar faces. Moreover, the contrast between the cover material and the substrate beneath the rough surface is supposed to be low. In this case, a modification of Stearns' formula based on Born approximation and Fourier techniques is derived for a special class of surfaces. This class contains the graphs of functions if the interface function is a radially modulated almost periodic function. For the Born formula to converge, a sufficient and almost necessary condition is given. A further technical condition is defined, which guarantees the existence of the corresponding far field of the Born approximation. This far field contains plane waves, far-field terms like those for bounded scatterers, and, additionally, a new type of terms. The derived formulas can be used for the fast numerical computations of far fields and for the statistics of random rough surfaces
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