Electrical Switching in Carbon Nanotubes  and Conformational Transformation               of Chain M...
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Electrical Switching in Carbon Nanotubes and Conformational Transformation of Chain Molecules. 2006. 8. 30. Jisoon Ihm School of Physics, Seoul National University. Collaborators. Sangbong Lee, Seungchul Kim, Byoung Wook Jeong (Seoul Nat’l Univ.)

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Jisoon ihm school of physics seoul national university

Electrical Switching in Carbon Nanotubes and Conformational Transformation of Chain Molecules

2006. 8. 30

Jisoon Ihm

School of Physics, Seoul National University


Collaborators

Collaborators

  • Sangbong Lee, Seungchul Kim, Byoung Wook Jeong (Seoul Nat’l Univ.)

  • Young-Woo Son ,Marvin Cohen, Steven Louie (Berkeley)


Jisoon ihm school of physics seoul national university

Basics:Substitutional Impurity in Metallic Carbon Nanotubes

Boron or Nitrogen

Tube axis


Jisoon ihm school of physics seoul national university

Electronic Structure of Metallic Armchair Nanotube

Band structure of a (10,10) single-wall nanotube ( LDA, first-principles pseudopotential method )


Jisoon ihm school of physics seoul national university

CBM

VBM


Jisoon ihm school of physics seoul national university

Tube axis


Jisoon ihm school of physics seoul national university

Conductance with Boron Impurity

Similarity to acceptor states in semiconductors

A

A

H.J. Choi et al, PRL 84, 2917(2000)


Jisoon ihm school of physics seoul national university

Conductance with Nitrogen Impurity

Similarity to donor states in semiconductors

D

D


Jisoon ihm school of physics seoul national university

I. Electrical switching in metallic carbon nanotubes

( Y.-W. Son, J. Ihm, etc., Phys. Rev. Lett. 95, 216602(2005) )


Jisoon ihm school of physics seoul national university

1. Motivation

  • Metallic and semiconducting carbon nanotubes are produced simultaneously.

C. Dekker, A. Zettl

Selection Problem!

  • Semiconducting nanotubes : easy to change conductance using gate

  • Metallic nanotubes: robust against impurities, defects, or external fffffffff fields (difficult to change conductance)


Jisoon ihm school of physics seoul national university

1. Motivations – cont’d

Is it possible to control the conductance of metallic single-wall carbon nanotubes?

S.B. Lee, A. Zettl

Interplay between defects and electric fields

electron flow


Jisoon ihm school of physics seoul national university

2. Calculational Method

2

: Landauer formalism

SCattering-state appRoach for eLEctron Transport (SCARLET)

H. J. Choi et al, PRB 59, 2267(1999), and in preparation


Jisoon ihm school of physics seoul national university

Nitrogen Boron

The electronic potential of N(B) is lowered. Levels of quasibound states move down.

The electronic potential of N(B) is raised. Levels of quasibound states move up.

3. B(N) doped (10,10) SWNT


Jisoon ihm school of physics seoul national university

4. Switching in B-N codoped (10,10) SWNT

B

N

  • Switching behavior: off/on ratio=607kΩ/6.4kΩ~100

  • Maximum resistance depends on the relative position between N and B.

  • Asymmetric resistance w.r.t. the direction of Eext


Jisoon ihm school of physics seoul national university

5. Scaling for larger (n,n) SWNT

∆H ∝ Eext · (diameter)2


Jisoon ihm school of physics seoul national university

6. Switching in (10,10) SWNT with Vacancies

  • Four carbon atoms are removed (Strong repulsive potential).

  • Doubly degenerate quasibound states at fermi level

  • Switching behavior: off/on ratio=1200kΩ/6.4kΩ ~200

  • Symmetric resistance w.r.t. the direction of Eext


Jisoon ihm school of physics seoul national university

6. Switching in (10,10) with Vacancies – cont’d

Quasibound states move up or down depending on the direction of Eext.


Summary

Summary

  • Conductance of metallic CNTs with impurities and applied electric fields is studied.

  • With N and B impurity atoms on opposite sides, asymmetric switching is possible using external fields.

  • With a large vacancy complex, symmetric switching is possible using external fields.


Jisoon ihm school of physics seoul national university

II. Conformational Transform of Azobenzene Molecules

( B.-Y. Choi et al., Phys. Rev. Lett. 96, 156106(2006) )


Jisoon ihm school of physics seoul national university

Azobenzene (AB) : C6H5-N=N-C6H5


Jisoon ihm school of physics seoul national university

Transformation between transAB and cisAB

(Voltage bias using STM)


Jisoon ihm school of physics seoul national university

Geometries of tAB


Jisoon ihm school of physics seoul national university

Geometries of cAB


Jisoon ihm school of physics seoul national university

Optimal geometry of tAB and cAB


Jisoon ihm school of physics seoul national university

STS for tAB and cAB


Jisoon ihm school of physics seoul national university

Disperse Orange 3 (NH2-C6H4-N=N-C6H4-NO2)


Jisoon ihm school of physics seoul national university

Flat geometry of cAB


Summary1

Summary

  • Electrical pulse is found to induce molecular flip between trans and cis structures.


Example of material design total reflection by three nitrogen impurities

Appendix

Example of MATERIAL DESIGN : totalreflection by three nitrogen impurities

Importance of geometric symmetry (equilateral triangle)

Doubly degenerate impurity states cause perfect reflection at 0.6 eV.

(Both even and odd states are fully reflected at same energy.)


Jisoon ihm school of physics seoul national university

Difference between Eext and impurity potential U

Lippman-Schwinger formalism:

Eigenstate |ψ> of Htot associated with the eigenstate |> of H0 with the same energy E (with impurity potential U at site a)


Jisoon ihm school of physics seoul national university

Projection on to the impurity |>

where

Reflection for the specific state |> :

Total transmission :

Resonance condition :


Jisoon ihm school of physics seoul national university

Effect of Eext : Green’s function itself changes.

: G0 projected at site a

With applied electric fields,

Suppose ∆H at site α is ∆E.

In other words, is G0(α;E) shifted by ∆E.


Jisoon ihm school of physics seoul national university

(10,10) SWNT with single attractive impurity of U=-5|t|


Changing e ext is different from changing u

(10,10) SWNT with NO Eext while changing the strength of the attractive potential, U.

EF

Changing Eext is different from changing U.

(10,10) SWNT with a single attractive impurity of U=-5|t| while changing Eext


Jisoon ihm school of physics seoul national university

SAMSUNG SDI FED – 2005 -


Power consumption of sed lcd pdp 36in

Power consumption of SED, LCD, PDP (36in)

Canon-Toshiba SED at CEATEC2004

SED

LCD

PDP


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