Coulomb Blockcade and Novel Conductance Quantization Related to 1D
Electron-electron Interaction in Nano-porous Alumina Film
Junji Haruyama*
Department of Electrical Engineering and Electronics,
Aoyama Gakuin University, Tokyo, JAPAN
This is an abstract
for a presentation given at the
Sixth
Foresight Conference on Molecular Nanotechnology.
There will be a link from here to the full article when it is
available on the web.
Recent progress of nano-fabrication technologies has successfully
brought observation of many attractive nano-phenomena. Coulomb blockade (CB)
which is a typical phenomenon originated from single electron tunneling is
one of such nano-phenomena. It has been well studied theoretically and
experimentally in many nano-tunnel junction systems, e.g. semiconductor
nano-tunnel junctions fabricated by nano-lithographies and crystal growth
methods like an artificial atom, metal nano-particle array like a glanular
film. The emergence of CB strongly depends on impedance of external
environment around the junction, particularly in single junction system.
Unless a high impedance block(>> resistance quantum) is much closely
connected to the junction, the CB is easily smeared out by the
electro-magnetic fluctuation from the external circuit. Hence it is the
core importance to study the relation between CB and physics of electron
transport in the external environment directly located to the junction.
Also conductance quantization (CQ) is very interesting nano-phenomenon
observable in some nano-structures, e.g. quantum hall effects, CQ in
quantum point contact. Although CQ with universal
value(i.e.2e2/h) has been well reported, its collapse has
recently attracted much attention. Some one-dimensional(1D) semiconductor
wires actually exhibited such collapse of universal CQ (so called
non-universal CQ:NUCQ), e.g. with value of (2e2/h)(1/4). One of
such structures is Tomonaga-Luttinger liquid (TLL) with
electron-electron(e-e) interaction and impurity scattering (i.e. dirty TLL).
The UCQ can be drastically collapsed in it depending on the wire length,
mean free path, temperature, etc.
In contrast, we have recently reported novel nano-fabrication
technique by utilizing nano-porous Alumina film template. Porous Alumina
film is grown through self-organizing process by simply anodizing pure
Aluminum film. It includes high packing density of pores like a honey-comb
with high uniformity and repeatability. We have successfully developed how
to control the structure parameters into nano-size order, e.g. pore
diameter of 5 nm, inter-pore spacing of 30 nm[1]-[3]. One can easily build up
varieties of unique nano-structure arrays by electrochemically depositing
some materials in the nano-pores, e.g. metals, semiconductors, organic
materials, superconductors. In this work, we, for the first time, report on
novel CB and NUCQ observed in such nano-strutures.
The nano-structure reported here consists of array of a long Ni
nano-wire/Al2O3 nano-tunnel junction/Al substrate.
The most unique point is in the long nano-wire (2 µm length and nm order
diameter) with tunnel junction only on the one end. In the sample with the
wire diameter around 12 nm, only a CB was observed originating from the
single tunnel junction, related to high impedance environment by e-e
interaction in the Ni nano-wire. The detailed temperature measurements of
the electrical characteristics revealed that the e-e interaction took
transition from the 3D to 1D regimes with reducing applied voltage and the
CB emerged in the 1D e-e interaction regime as the e-e scattering rate
drastically decreased. This suggests that internal electrical fluctuation
by strong e-e interaction smears the CB out even under high impedance
environment. Hence this CB voltage is much different from that in orthodox
theory (i.e. V=e/2C). On the other hand, in the sample with wire diameter
around 7 nm, novel NUCQ was observed with value of
(2e2/h)(1/200)2(-n) in addition to the CB. The
conductance (G)-V curve was much asymmetric and the relation mentioned above
is fit only in the +V region. In contrast, clearer G plateau can be
observed with different relation in the -V region. This NUCQ emerged only
in the 1D e-e interaction regime of the Ni-wire mentioned above. Besides it
could be observed only in the 7 nm wire-diameter sample and the quantized
value was extremely small as mentioned above. Based on those, the
possibility of dirty TLL in the Ni nano-wire is discussed.
Both the CB and the NUCQ reported in this work are much novel. None
has reported such effects because it can emerge only in much long nano-wire
with single tunnel junction and only our method was much suitable for
making such structure. This is one of the examples of unique
nano-structures fabricatable by using our method. This nano-fabrication
technique by using porous Alumina film will open up more chances to find
out novel nano-phenomena.
References
- Tager, A.; Routkevitch, D.; Haruyama, J; et al. (1996) Future
Trends in Microelectronics edited by S.Luryi, J.M.Xu, and A.Zalavsky, NATO
ASI Series E-323, pages 171-183. Nonlithographic fabrication and physics of
nanowire and nanodot array devices -present and future-
- Davydov, D.; Haruyama, J.; Routkevitch, D.; Ellis, D.; Statt, B.W.; Moskovits, M.; and Xu, J.M. (1998) Phys.Rev.B, Vol.57(21), pages 13550-13553. Nonlithographic nanowire-array tunnel devices: fabrication, zero-bias anomalies, and Coulomb blockade
- Haruyama, J.; Davydov, D.; Routkevitch, D.; Ellis, D.;
Statt, B.W.; Moskovits, M.; and Xu, J.M. (1988) Solid-state Electronics as
the proc. NPE'97, Vol.42(7-8), pages 1257-1266. Coulomb blockade in
nanojunction array fabricated by nonlithographic method
*Corresponding Address:
Junji Haruyama
Department of Electrical Engineering and Electronics, Aoyama Gakuin University
6-16-1 Chitosedai, Setagaya, Tokyo, 157-8572 JAPAN,
phone: 81-35384-6411, fax 81-35384-6411
email: [email protected]
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