Vertical resonant tunneling transistors with molecular quantum dots

Lunes, Septiembre 4, 2017 - 12:00
Place: 
Donostia International Physics Center
Who: 
Ryoma Hayakawa (NIMS, Tsukuba, Japan)
Source Name: 
DIPC

Vertical resonant tunneling transistors with molecular
quantum dots

Ryoma Hayakawa

International
Center for Materials Nanoarchitectonics (WPI-MANA)

National
Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan

HAYAKAWA.Ryoma@nims.go.jp

Quantum
molecular devices hold considerable promise for the construction of new data
processing architectures that cannot be achieved using current Si technology. Although the
relevant basic quantum transport properties have been examined by specific
methods such as scanning probe and break-junction techniques, these
methodologies are not compatible with current complementary metal-oxide–semiconductor (CMOS) applications.

In this regard, we have proposed to use organic molecules as quantum
dots in double tunnel junctions.1-3 A striking feature of the proposed system is that the tunnel junction is
composed of a MOS structure, which is the heart of current Si transistors.
Thus, the structure satisfies both requirements above, namely, the integration
of molecular functions and close affinity with current CMOS devices. The
molecules are embedded in the insulating layers, which consist of a silicon
oxide (SiO2) layer and an aluminum oxide (Al2O3)
layer (Fig. (a)). The number
density of molecules was estimated in the order of 1012-1013
cm-2, and we have observed
clear resonant tunneling through discrete energy levels of the embedded molecules.1 This finding enabled the following attractive manipulations of the
tunneling currents, which are unique features of organic molecules: the employment
of binary molecules, including copper phthalocyanine and fluorinated
phthalocyanine, produced multilevel control of the resonant tunneling;2
and the adoption of diarylethene photochromic molecules allowed for optical
manipulation of the tunneling, with the current being reversed by alternating
ultraviolet and visible light irradiation.3

Futhermore, we employed abovementioned
double tunnel junctions as the transistor channels in vertical resonant
tunneling transistor.4
The transistors enabled multilevel
operations induced by the discrete energy levels of the molecules. The
effective gate modulation of the resonant tunneling currents was produced by
depletion layers in the Si substrates. Thus, the proposed
device has potential to integrate molecular functions into future CMOS devices,
and to deliver unique device operations unobtainable with inorganic quantum
dots.

References

1)    R. Hayakawa and Y. Wakayama et
al.
, Adv. Funct. Mater. 2011, 21,
2933-2937.

2)    R. Hayakawa
and Y. Wakayama et al., ACS Appl. Matter. Interfaces 2013, 5, 11371-11376.

3)    H.-S. Seo , R. Hayakawa and Y. Wakayama et al., J. Phys. Chem. C 2014,
118, 6467-6472.

4)    R. Hayakawa and Y. Wakayama et al., Nanoscale 2017 (under
review).

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