E. S. Soldatov

Single-electron transistor based on a single cluster molecule at room temperature

A single-electron molecular transistor is implemented at room temperature on the basis of a stable Langmuir monomolecular film consisting of a mixture of stearic acid and carborane clusters. Control of the tunneling current with the aid of an independent voltage source is recorded at room temperature. The results are compared with the “orthodox” theory of single-charge electronics.

Molecular clusters as building blocks for nanoelectronics: the first demonstration of a cluster single-electron tunnelling transistor at room temperature

This work is the result of coherent effort of a multi-disciplinary research team working for a considerable number of years in the former USSR in the area of nanocluster molecular electronics. For the first time the successful demonstration of a single-electron tunnelling transistor working reliably at room temperature and based on a single molecular metallorganic cluster is presented. A broad spectrum of different molecular clusters was investigated. Our group has developed a complete cycle of custom-designed molecular cluster manufacturing, deposition, characterization and modification of nanoelectronic devices based on a single molecular cluster. It was shown that the atomic and electronic structure of nanoclusters containing from 3 up to 23 metal atoms had no crucial importance for the transistor fabrication. At the same time extensive research into characteristics of nanoelectronic devices based on single molecular clusters and their tunnelling properties is summarized.

STM study of morphology and electron transport features in cytochrome c and nanocluster molecule monolayers

The morphology and electron tunneling through single cytochrome c and nanocluster Pt(5)(CO)(7)[P(C(6)H(5))](4) molecules organized as monolayer Langmuir-Blodgett (LB) films on graphite substrate have been studied experimentally using scanning tunneling microscopy (STM) and spectroscopy techniques with sub-nanometer spatial resolution in a double barrier tunnel junction configuration STM tip-monomolecular film-conducting substrate at ambient conditions. STM images of the films revealed globular structures with characteristic diameters (approximately 3.5 nm for the protein molecule and approximately 1.2 nm for the nanocluster). The spectroscopic study by recording the tunneling current-bias voltage (I-V) curves revealed tunneling I-V characteristics with features as steps of different width and heights that are dependent on the STM tip position over the molecule in the monolayer, giving evidence for sequential discrete electron-tunneling effects with the combination of the single electron Coulomb-charging energy and the electronic energy level separation (molecular spectrum) in such immobilized metalloprotein and nanocluster structures that can be of interest for the development of bioelectronic and hybrid functional nanosystems.

Interfacial nanofabrication strategies in development of new functional nanomaterials and planar supramolecular nanostructures for nanoelectronics and nanotechnology

Clusters, nanoparticles, nanowires, long molecules as nanotubes and polynucleotides, and functional supramolecular nanostructures are currently considered as potential building blocks for nanotechnology and nanoelectronic devices and circuits, and development and introduction of new methods to control effectively their structure, composition and nanoscale organization are necessary. Here we describe a number of new nanofabrication methods which are based on the monolayer techniques, biomimetic principles, interfacial reactions and interactions. The methods allowed to produce new stable reproducible planar one-dimensional and two-dimensional arrays of ligand-stabilized nanoclusters and nanoparticles on solid substrates, ultrathin polymeric nanoscale-ordered mono- and multilayer quasi-crystalline and nanocomposite films, planar polymeric complex films with integrated DNA and inorganic building blocks as semiconductor and iron oxide nanoparticle quasi-linear arrays and nanowires. Transmission electron microscopy, STM and AFM techniques were used to characterize the fabricated nanostructures. Effects related to discrete electron tunneling were observed in the monolayers of nanoclusters and small gold nanoparticles at room temperature using STM.

Langmuir–Blodgett films in the development of high temperature single electron tunneling devices

Abstract Mixed Langmuir–Blodgett (LB) films consisting of inert molecular stearic acid matrix and embedded cluster molecules (carborane and organo-metallic molecules) were used to create reproducible, stable, ordered, planar nanostructures with different systems of electron tunnel junctions. All clusters were chemically synthesized and hence had atomically equal structure and reproducible properties. Mixed monolayers on the water surface were studied. Formed molecular structures were studied at room temperature using scanning tunneling microscopy and effects related to single-electron tunneling and energy quantization of electrons were observed in such structures.

Effect of compression of a stearic acid monolayer on interfacial binding of copper ions and cluster formation

Abstract The effect of compression of a stearic acid Langmuir monolayer on the interaction of copper ions with the monolayer and on the formation of interface clusters has been studied as functions of pH and ionic content of the water subphase. Copper binding was estimated by direct electron paramagnetic resonance measurements of ion concentrations in the water subphase. A scanning tunnelling microscopy study of monolayer Langmuir-Blodgett films, deposited on graphite substrates, gave evidence for the formation of nanosized clusters on the monolayer surface. The data obtained showed that the interaction of the monolayer with copper ions and the accompaning cluster formation processes were determined by the arrangement, order and mobility of the stearic acid molecules in the monolayer and the electrostatics at the interface.

The design, fabrication and characterization of controlled-morphology nanomaterials and functional planar molecular nanocluster-based nanostructures

Abstract New nanofabrication methods based on the monolayer techniques, biomimetic principles, interface reactions and interactions have been developed. The formation and deposition of the mixed Langmuir monolayers composed of inert amphiphile matrix and guest ligand-stabilized metal-core nanocluster molecules allowed to obtain ordered stable reproducible planar monomolecular nanocluster-based nanostructures on solid substrates. The decomposition of similar metal–organic precursor compounds in the mixed Langmuir monolayers at the gas–liquid interface resulted in the initiation of two-dimensional growth of inorganic nanoparticles in the plain of monolayer. Gold and iron-containing nanoparticles were synthesized and characterized by scanning probe microscopy and transmission electron microscopy techniques. Effect of external applied field on the shape of two-dimensionally grown magnetic nanoparticles was observed. Effects related to discrete electron tunneling were observed in the monolayer structures of nanocluster molecules and gold nanoparticles at room temperature using STM.

Structure and properties of Langmuir-Blodgett films containing cluster molecules

Abstract An approach based on the use of mixed Langmuir–Blodgett (LB) films containing various chemically synthesized nanocluster molecules has been proposed in order to create single-electron transfer model systems functioning at room temperatures. The nanoclusters are shown to form ordered structures (quasilinear chains, two-dimensional arrays, etc.) in such monolayers deposited onto the solid substrates. The tunnel current–bias voltage ( I – V ) characteristics of isolated cluster molecules Pt 5 (CO) 6 (PPh 3 ) 4 taken at 300 K exhibit rich structures resulting from the interplay between Coulomb charging effects and discreteness of an electronic spectrum of the cluster. The platinum Pt 5 (CO) 6 (PPh 3 ) 4 clusters appear to posses surface-active properties and can form stable homogeneous Langmuir monolayers on the water surface. Such monolayers can be effectively transferred onto the solid substrates so that corresponding multilayer LB films are obtained. X-ray difractograms recorded for those films show a number of Bragg peaks caused by the ordered layered structure of the films. Close values of intensity of the second harmonic generation measured for the mono- and 11-layer LB films of the platinum clusters give evidence of the centrosymmetrical Y-type packing of the cluster molecules in multilayer LB films. The pertinent theoretical model of cluster molecule packing in such films has been proposed.

Fabrication and properties of carboran clusters contained in stearic acid LB films and possible applications for single electron electronics

Abstract Correlated discrete transfer of single electrons in ultrasmall tunnel junctions is of great interest for applications in molecular electronics. We report single-electron tunnelling at 300 K in the double tunnel junction system “graphite substrate-carboran cluster-STM tip”. The problem of reliably fixing clusters on the graphite surface has been solved by means of cluster incorporation into a stearic acid LB (Langmuir-Blodgett) monolayer matrix. We obtained compression isotherms of mixed monolayers with varying molar ratio [stearic acid]:[clusters]. STM images of deposited mixed films revealed that the clusters formed a regular structure.

Molecular cluster based nanoelectronics

The use of molecular clusters as a basis of molecular single-electronic systems is considered experimentally and theoretically. The Langmuir-Blodgett formation and scanning tunneling microscope study of structures with chemically different cluster molecules is described. I-V curves and control curves of molecular single-electron transistors based on various single molecules were studied at room temperature. Comparison of experimental I-V curves with simulated ones allows us to identify a regime of slow energy relaxation of electrons in experimental transistors. Experimental study of electron transport through the planar molecular nanosystems has shown a correlated character of electron tunneling in such systems.