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F Remacle

Publications and source records attributed to F Remacle.

4 recordsLinked to original sources
PubMed2002

Quantum dot artificial solids: understanding the static and dynamic role of size and packing disorder.

This perspective examines quantum dot (QD) superlattices as model systems for achieving a general understanding of the electronic structure of solids and devices built from nanoscale components. QD arrays are artificial two-dimensional solids, with novel optical and electric properties, which can be experimentally tuned. The control of the properties is primarily by means of the selection of the composition and size of the individual QDs and secondly, through their packing. The freedom of the architectural design is constrained by nature insisting on diversity. Even the best synthesis and separation methods do not yield dots of exactly the same size nor is the packing in the self-assembled array perfectly regular. A series of experiments, using both spectroscopic and electrical probes, has characterized the effects of disorder for arrays of metallic dots. We review these results and the corresponding theory. In particular, we discuss temperature-dependent transport experiments as the next step in the characterization of these arrays.

Journal Article↗
PubMed2001

Logic gates using high Rydberg states.

Connected logic gates can be operated on the levels of one molecule by making use of the special properties of high Rydberg states. Explicit experimental results for the NO molecule are provided as an example. A number of other options, including that of several gates concatenated so as to operate as a full adder, are discussed. Specific properties of high Rydberg states that are used are: their autoionization is delayed so that they can be distinguished from direct multiphoton ionization, during their long life such states also can decay by energy transfer to the molecular core in a way that can be controlled by the judicious application of very weak external electrical fields, and the Rydberg states can be detected by the application of an ionizing electrical field. The combination of two (or three) color photons with and without external weak fields allows the construction of quite elaborate logic circuit diagrams and shows that taking advantage of the different intramolecular dynamics of levels that differ by their excitation enables the compounding of logic operations on one molecular frame.

Journal Article↗
PubMed2000

Architecture with designer atoms: simple theoretical considerations.

The distinct electronic states of assemblies of metallic quantum dots are discussed in a simple approximation where each dot is mimicked as an "atom" that carries one valence electron. Because of their large size, the charging energy of the dots, I = energy required to add another electron, is much smaller than for ordinary atoms. The Coulomb blocking of charge migration is therefore easier to overcome. For the theory, however, this is a challenge, because ionic states, which are typically higher in energy, come down, so the density of electronic states is high, and special methods need to be adapted. Quantum dots are prepared by wet chemical methods and accordingly are not quite identical. They will have a size distribution that can be narrow (when the dots can be assembled into an ordered array) or broad. Other sources of disorder are packing imperfections, which are characteristic of a wider size distribution, ligand deformations, and chemical unevenness. Two experimental control parameters are the size of the dots and the spacing between them. We discuss the combined effects of the low charging energy and disorder and examine the distinct electronic phases that can be realized.

Chemical Phenomena↗