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Novel Carbon Nanotube Array in Nano-porous Alumina: Weak Localization and Coulomb Blockade

Junji Haruyama*, Izumi Takesue, Keisuke Ohta, and Ryoji Koganei

Aoyama Gakuin University, Dept. Electrical Engineering and Electronics
Tokyo 157-8572 Japan

This is an abstract for a presentation given at the
Seventh Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is available on the web.

 

We firstly report on coexistence of weak localization (WL) and Coulomb blockade (CB) in an array of Carbon naotube/single nano-tunnel junction. The array of Carbon nanotube (CN) was fabricated by novel method, i.e. by using nano-porous Alumina film template. We have reported on mesoscopic phenomena by depositing metals into the nano-pores of the Alumina film[1]. In this work, CN was for the first time successfully deposited inside nano-pores by vapor phase method[2]. This method results in the following two different features of CN from past reports.

  • The CNs are arrayed in parallel with high packing density and uniformity.
  • The top of CN is not closed in this case.
In addition, since these pores have tunnel barrier layer between the bottom and Al substrate, this system is array of CN/single tunnel layer. Electrical features were measured by applying DC two terminal voltage between the top of CN and the Al substrate.

Temperature (T) dependence of conductance (G) exhibited a linear G-Log(T) relation at higher T region. In contrast, it shows a linear G-T relation. The linear G-Log(T) indicates presence of WL or electron-electron interaction. Magnetic field (H) dependence of G exhibited a linear G-Log(H) at higher H region. In contrast, it exhibited a negative magnetoconductance at low H region. This strongly suggests present WL. The result is consistent with the past report of multi-shell CN[3]. Here, the linear G-T relation indicates present CB in single tunnel junction[1]. This coexistence of WL and CB implies the following interesting facts

  • Phase coherence is conserved despite of present single tunnel junction.
  • WL plays a role of high impedance environment for the CB.
These are quite novel finding on which none reported.

This method makes easy measurement of arrayed CN possible. Observed results are also quite attractive. Besides more unique features are expected if some materials are deposited inside CN. Therefore, this novel CN array is promising both for mesoscopic physics and for device application.

References
  1. J.Haruyama, D.Davydov, et al., Solid-state Electronics, 42, 1257 (1998); D.Davydov, J.Haruyama, D.Routkevitch, et al., Phys.Rev.B, 57(21), 13550 (1998)
  2. J.Li,.M.Moskovits, et al., Chem.Mater., 10, 1963 (1998)
  3. L.Langer, V.Bayot et al., Phys.Rev.Lett., 76, 479 (1996)

*Corresponding Address:
Junji Haruyama
Aoyama Gakuin University, Dept. Electrical Engineering and Electronics
6-16-1 Chitosedai, Setagaya, Tokyo 157-8572 Phone: 81-35384-6411; Fax: 81-35384-6411 Japan
E-mail: J-haru@ee.aoyama.ac.jp



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