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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