Yuri Shunin

Resistance simulations for junctions of SW and MW carbon nanotubes with various metal substrates

This theoretical study focuses on junctions between the carbon nanotubes (CNTs) and contacting metallic elements of a nanocircuit. Numerical simulations on the conductance and resistance of these contacts have been performed using the multiple scattering theory and the effective media cluster approach. Two models for CNT-metal contacts have been considered in this paper: a) first principles “liquid metal” model and b) semi-empirical model of “effective bonds” based on Landauer notions on ballistic conductivity. Within the latter, which is a more adequate description of chirality effects, we have simulated both single-wall (SW) and multi-wall (MW) CNTs with different morphology. Results of calculations on resistance for different CNT-Me contacts look quantitatively realistic (from several to hundreds kOhm, depending on chirality, diameter and thickness of MW CNT). The inter-wall transparency coefficient for MW CNT has been also simulated, as an indicator of possible ‘radial current’ losses.

Simulation of electromagnetic properties in carbon nanotubes and graphene-based nanostructures

As carbon nanotubes (CNT) and graphene nanostructures (GNR) constitute the basis of high-speed nanoelectronics and nanosensors, we examine the fundamental properties of var- ious CNT-metal (Me), GNR-Me, and CNT-graphene interconnects. The cluster approach based on the multiple scattering theory as well as effective medium approximation were used to model the dispersion law, electronic density of states (DOS), and conductivity, etc. Multiple scattering problems were solved for nanostructures with radial (quantum dots) and axial (nanowires, nano- tubes) symmetry. Interconnect capacitances and impedances have been evaluated in the GHz and THz regimes. Parametrical numerical simulations of conductivity were carried out for zig-zag ðm;0Þ, armchair ðm;mÞ, and chiral ðm;nÞ CNTs, and the sensitivity of conductivity to the local electronic DOS in CNTs with local impurities (N and B atoms) was demonstrated. CNTs, CNT- Me, and GNR-Me based nanostructures are prospective nanosensor structures.

Simulation of Fundamental Properties of CNT- and GNR-Metal Interconnects for Development of New Nanosensor Systems

Cluster approach based on the multiple scattering theory formalism, realistic analytical and coherent potentials, as well as effective medium approximation (EMA-CPA), can be effectively used for nano-sized systems modeling. Major attention is paid now to applications of carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) with various morphology which possess unique physical properties in nanoelectronics, e.g., contacts of CNTs or (GNRs) with other conducting elements of a nanocircuit, which can be promising candidates for interconnects in high-speed electronics. The main problems solving for resistance C-Me junctions with metal particles appear due to the influence of chirality effects in the interconnects of single-wall (SW) and multi-wall (MW) CNTs, single-layer (SL) and multi-layer (ML) GNRs with the fitting metals (Me = Ni, Cu, Ag, Pd, Pt, Au) for the predefined carbon system geometry. Using the models of ‘liquid metal’ and ‘effective bonds’ developed in the framework of the presented approach and Landauer theory, we can predict resistivity properties for the considered interconnects. We have also developed the model of the inter-wall interaction inside MW CNTs, which demonstrates possible ‘radial current’ losses. CNT- and GNR- Metal interconnects in FET-type nanodevices provide nanosensoring possibilities for local physical (mechanical), chemical and biochemical influences of external medium. At the same time, due to high concentrations of dangling bonds CNT- and GNR- Metal interconnects as interfaces are also considered as electrically, magnetically and chemically sensitive elements for novel nanosensor devices.

Theoretical Simulations on Electric Properties of CNT-Me and GNR-Me Interconnects Using Effective Media Approach

Abstract To overcome disadvantages of nowadays microtechnology, a further miniaturization of electronic devices, high integration level as well as increase of both operation frequencies and power density is required, including the use of adequate materials and innovative chip interconnects. Due to their unique physical properties, especially due to a ballistic (without losses) mechanism of conductivity, carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) attract a permanently growing technological interest, for example, as promising candidates for nanointerconnects in a high-speed electronics.

Graphene, Fullerenes, Carbon Nanotubes: Electronic Subsystem

This chapter introduces the reader to the analysis of the structural and electronic system properties of various carbon allotropes (CNT, graphene) and several molecular derivatives. The genesis of the electronic system formation is investigated in detail. Non-regular defected nanocarbon systems are considered for possible applications in different fields, including energy storage; chemical, biochemical and electrochemical sensing; water purification; and catalysis.

Surface Nanophysics: Macro-, Meso-, Micro- and Nano-approaches

The surface factor is very important for manipulating objects at a nanoscale. Thermodynamic behaviour is observed from the classical point of view, and conditional division into macro-, meso-, micro- and nano-approaches is presented. Processes of physical and chemical adsorption on the surface are presented from the energy and structure aspects. The occurrence of electronic states of the surface is presented from the classical point of view in comparison with molecular electronic states. One of the most important non-invasive optical methods to investigate nanoparticles is the surface plasmon resonance (SPR), which is quite useful for practical detection of nanoparticles in the surrounding environment. The interaction of light with nanoparticles is discussed within the framework of a nanoscale process. Nanoshells as practical implementation of nanosurface phenomena are discussed.

Nanosensor Systems Simulations

The chapter presents functionalized CNT and GNR nanostructures as the basis for the creation of physical, chemical and biochemical nanosensors. We have shown in our simulations the sensitivity of electron conductivity of FET-type nanodevices (based on CNTs and GNRs) to local doping by nitrogen and boron. This phenomenon provides the prospective of creating nanosensors.

Classification and Operating Principles of Nanodevices

The chapter presents and explains the classification of sensors in accordance with their physicochemical principles of functioning, as well as the types of recognition. Several prototypes of physical, chemical and biosensors based on polar molecular compounds such as indandione, fluorene and carbazole derivatives are described from the point of view of their structure and energy. One of the most important applications of nanosensitive materials is realized in the class of memory nanodevices. The realization of bistability in molecular or layered derivatives is usually carried out through processes based on tautomers and conformers, as well as phase transition processes. Typical examples of biomolecular rotary machines are shown. Nanotransducers principles, nanoaerogels and nanocomposites applications are also reviewed. Typical examples of biomolecular rotary machines are presented and the principles of nanotransducer operation are explained, and application of nanoaerogels and nanocomposite materials is considered.

CNT and Graphene Growth: Growing, Quality Control, Thermal Expansion and Chiral Dispersion

The chapter presents and discusses the production of graphene sheets of carbon nanotubes (CNT) of various types. The Iijima arc discharge method, following the purification methods, is described identifying advantages and disadvantages. Several types of non-regularities such as the Stone–Wales defect and corner effect, which locally increases reactivity, are described from the structural point of view. The laser ablation method is presented as one of the most prominent methods in the production of CNTs. The catalytic chemical vapour deposition (CVD) method is a very effective tool for the controlled production of different carbon shells. The sporadic and simulated growth of CNTs depends on thermodynamic conditions (temperature, vapour pressure) as well as on the surface properties (size and the type of catalyst particles). The chapter also presents the model of magnetically stimulated CNT growth for a special case of Fe–Pt metallic nanoparticles, which have unique magnetic properties. We expect that in the presence of a magnetic field the growth of CNTs will be more determined from the point of view of possible CNT morphologies.

Introduction to Non-regular Nanosystems

The chapter presents a short description of the main topics in non-regular nanosystems. In general, the scientific content of the discussed problems is based on the research interests of the authors of this book. Non-regularity is considered as a basic stimulus for the operational abilities of novel nanomaterials.