Biomedical Engineering Reference
In-Depth Information
energy
LUMO
Au, Ag (-4.3 eV)
G* (-4 eV)
A* (-4.2 eV)
C*,T*(-4.6 eV)
E
g
= 3.75 eV
Pt (-5.36 eV)
G (-7.75 eV)
A (-7.95 eV
C, T (-8.3) eV
HOMO
contact barrier
Fig. 1.35
Work functions of metals and DNA bases
+
-
DNA
Pt
Si
3
N
4
SiO
2
Si
Fig. 1.36
DNA molecule trapped between gap electrodes for conduction measurements
The wide bandgap semiconducting behavior of dsDNA was demonstrated in
Porath
et al.
(
2000
), in which it was considered that there is an overlap of orbitals of
neighboring base pairs in a 10.4-nm-long dsDNA structure, which covers the gap
between two Pt electrodes and contains 30 base pairs of the same type (poly(G)-
poly(C)). The DNA was trapped by electrostatic trapping when a bias was applied
between the two electrodes (see Fig.
1.36
).
The 1lof DNA from a dilute aqueous solution, which contained one DNA
molecule per .100 nm/
3
, was trapped between the electrodes. The gap between
electrodes is 8 nm and was obtained by EBL. The I
V characteristic of the device,
similar to that of a Zenner diode, is displayed in Fig.
1.37
. The authors in
Porath
et al.
(
2000
) have attributed this behavior to the offset between the Fermi level of
the nanogap electrodes and the molecular energy bands of DNA (see Fig.
1.35
).
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