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M. Senami and A. Fukushima
local region, vacancy, interface, and impurity for condensed matter and functional
group and bonding to other molecules for molecular devices.
Gate leakage current through dielectric thin film can be explained by the
percolation model [2, 3]. In this model, almost all leakage current flows through
defect chain in a film. In other words, observable leakage current for thin films
is concentrated on a very restricted region. In another example, benzenedithiol
is studied by many groups as prototype for future molecular electronics devices.
Experimental measured values of conductance of Au-benzene-1,4-dithiolate-Au
junction show very wide range, 10 −4 − 1[e 2 / ¯
h], [4–9]. This conductance is
considered to be heavily dependent on connections between Au atoms in electrodes
and sulfur atoms [10–12]. In addition, if π -bonding is broken by adding a functional
group, conductance is decreased significantly [13]. Therefore, analysis of a specific
local region in a material is important for nanosize device materials.
In Fig. 3.1, the difference between quantum mechanics and quantum field theory
is schematically depicted. Particularly, the local description of the equation of
Fig. 3.1 Schematic picture of the difference between quantum mechanics and quantum field
theory. The symbol, ˆ
O, is an operator and ˆ
H is the Hamiltonian. Wave function in quantum
mechanics is denoted by ψ, and field operator is denoted by ˆ
ψ
M. Senami and A. Fukushima
local region, vacancy, interface, and impurity for condensed matter and functional
group and bonding to other molecules for molecular devices.
Gate leakage current through dielectric thin film can be explained by the
percolation model [2, 3]. In this model, almost all leakage current flows through
defect chain in a film. In other words, observable leakage current for thin films
is concentrated on a very restricted region. In another example, benzenedithiol
is studied by many groups as prototype for future molecular electronics devices.
Experimental measured values of conductance of Au-benzene-1,4-dithiolate-Au
junction show very wide range, 10 −4 − 1[e 2 / ¯
h], [4–9]. This conductance is
considered to be heavily dependent on connections between Au atoms in electrodes
and sulfur atoms [10–12]. In addition, if π -bonding is broken by adding a functional
group, conductance is decreased significantly [13]. Therefore, analysis of a specific
local region in a material is important for nanosize device materials.
In Fig. 3.1, the difference between quantum mechanics and quantum field theory
is schematically depicted. Particularly, the local description of the equation of
Fig. 3.1 Schematic picture of the difference between quantum mechanics and quantum field
theory. The symbol, ˆ
O, is an operator and ˆ
H is the Hamiltonian. Wave function in quantum
mechanics is denoted by ψ, and field operator is denoted by ˆ
ψ