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Correlation of Nanotubes Parameters

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Correlation of Electron Properties of Individual Carbon Nanotubes, Atomic Structure and Parameters of Catalytic Synthesis

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics
  • INF-ELE/Microelectronics and Optoelectronics/Information and Communications
  • MAT-ALL/High Performance Metals and Alloys/Materials
  • MAT-CER/Ceramics/Materials
  • MAT-COM/Composites/Materials
  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
8 Project completed

Registration date
28.04.2003

Completion date
21.03.2007

Senior Project Manager
Endrullat B

Leading Institute
Institute of Microelectronics Technology and High Purity Materials, Russia, Moscow reg., Chernogolovka

Supporting institutes

  • VNIIKhT (Chemical Technology), Russia, Moscow\nInstitute of Problems of Chemical Physics, Russia, Moscow reg., Chernogolovka

Collaborators

  • Northwestern University / Department of Mechanical Engineering, USA, IL, Evanston\nGeorgia Institute of Technology / School of Materials Science and Engineering, США, GA, Atlanta\nMER Corporation, USA, AZ, Tucson

Project summary

The goal of the project is to study of the correlation between electron properties of inpidual carbon nanotubes with their atomic structure and conditions of catalytic synthesis.

Carbon nanotubes discovered by Iijima in 1991 possess unique electrical properties which have no analogy among other solid state structures. Among carbon nanotubes single-walled nanotubes have the simplest structure composed of a graphene monolayer rolled up in the cylinder. These nanotubes appear as molecular wires. Depending on geometry of rolling up (chirality) and diameter, the nanotubes can be metals and narrow- or wide-band semiconductors. In the metal state the nanotubes have conductivity exceeding that of copper and are able to conduct current up to 1010 А/cm2 at the room temperature. Such properties and unique small dimensions (down to 0.4 nm in diameter) make them very promising materials to be used in molecular electronics. The maim obstacle for such application is impossibility to produce nanotubes of predicted chirality and, consequently, desirable properties. Though numerous attempts to perform a controlled nanotube growth were made, all of them were unsuccessful.

The attempts are based on varying size and content of catalytic species used in the nanotube growth. The same scheme was used: a simultaneous growth of a great number of nanotubes on numerous catalytic particles. The position remained principally the same if domains of catalytic material of several micrometers in size were prepared by lithographic technique since each domain contained a great number of catalytic particles on which tens and hundreds of nanotubes were grown.

The project suggests a fundamentally new approach to solve the problem: the study of only SINGLE nanotube growth on a SINGLE catalytic particle of few nanometers in size, isolated by the method of sub-10 nm lithography from the deposited islanded film, and the study of electronic properties of namely this nanotube. This investigation suggests the study of nanotube and metal particle atomic structures, the nanotube-particle interface and nanotube chirality in high resolution electron microscope parallel to electric measurements. Such a combine investigation is possible due to the unique technique developed by us that consists in applying self-supported nanotubes thrown over a prepared hole in a thin insulating SiO2/Si3N4 membrane performing as a support. Such a technique has already been used by the participants in the study of properties and structure of inpidual nanotubes thrown over the hole using a laser ablation method. This technique shall be further developed in the project: attention shall be focused on a DIRECT catalytic synthesis of nanotubes above the hole directly in a growth set up.

It is planned to study the nanotube growth on single catalyst particles of a sub-nanometer size. Such a particle that appears as a cluster of a deposited domain film and can be isolated in a given local place using high resolution electron lithography. 3d-, 4d- and 4f- transition metals are suggested to be used as catalytic materials. Catalytic particles shall be prepared by electron beam evaporation of a target or vapor deposition as well as and liquid impregnation of prepared nanometer holes in a support using metallocenes, carbonyls, phthalocyanines and other reagents as precursors. The resulting metallic nanoparticles allow the study of the dependence of structural parameters of the nanotubes on the structure of catalytic particles and a nanotube/particle interface.

The synthesis of nanotubes of various diameter and chirality on nanometer-size catalytic particles of different atomic structure is also suggested to be performed using pyrolysis of hydrocarbons, which have different decomposition temperature, strongly diluted by inert gas. Aromatic and unsaturated hydrocarbons shall be used as a source of carbon. Argon, helium, and hydrogen are to be used as diluents. The application of promoters (thiophene, alkylmercaptane and ammonium) can be used as well. Besides, the modified technique of nanotube growth by arc discharge evaporation of graphite is planned to be used to obtain nanotubes. We suggest to insert a substrate with prepared catalytic nanoparticles deposited in the prepared nanoholes in the electron resist, into the zone with a hot carbon vapor formed as a result of graphite evaporation in the electric arc. The ability to control ionized carbon vapor flow by electrical and magnetic field is also planed to employ. Experiments with bimetallic catalytic particles are also planned.

Stages of the project are following:


1. Development of procedures to prepare catalytic nanoparticles
2. Electric arc synthesis of single-walled nanotubes (SWNT)
3. Pyrolytic synthesis of nanotubes on single-component catalysts
4. Electron microscopy and electrical study of nanotubes and nanotube/catalytic nanoparticle interface
5. Synthesis of nanotubes on two-component catalysts
6. Development of techniques for synthesis of nanotubes of desirable size and chirality
7. Investigation of conductivity of resulting nanotubes
8. Determination of correlation between electronic properties of carbon nanotubes, their structure and parameters of synthesis

Project realization allows us to acquire fundamental knowledge to estimate the perspectives of the design of molecular electronics based on carbon nanotubes and develop a scientific and technological basis to create electron devices based on the wave electron transport through the carbon nanotubes.

Main expected results:


1. Correlation of electron properties of carbon nanotubes with the type of their atomic structure will be found.
2. Correlation of the diameter and the chirality of nanotubes with the structure of nanotube/catalytic particle interface will be established.
3. Mechanism of carbon nanotube growth will be proposed and optimal synthesis conditions will be defined.
4. Methods to obtain inpidual nanotubes at the desirable substrate place will be developed.
5. Techniques of growth of nanotubes of desirable electron and structural properties will be developed.
6. Scientific and technological grounds of the creation of molecular electronics elements based on the one-dimensional wave electron transport through the carbon nanotubes will be developed.
7. Data base devoted to the properties of the created elements of molecular electronics will be presented.

The project involves highly qualified participants, namely, specialists in materials science and the design of nanomaterials. The goals and objectives of the project fully comply with those of ISTC.


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